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Chapter 5 Flashcards

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1
Q

Does metabolism change between humans and smaller organisms?

A

No, it does not change

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2
Q

What is the definition of metabolism?

A

The sum total of all chemical reactions in a cell

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3
Q

What is metabolism?

A

The buildup and breakdown of nutrients within a cell.

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4
Q

What do metabolic chemical reactions provide?

A

Energy and substances that sustain life.

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5
Q

What are the two key players in metabolism?

A

Enzymes and adenosine triphosphate (ATP).

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6
Q

What is the role of enzymes in metabolism?

A

They catalyze reactions for specific substrates.

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7
Q

What is a substrate?

A

The specific molecule an enzyme acts on.

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8
Q

What is a product?

A

The new substance formed after an enzymatic reaction.

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9
Q

What happens to a substrate during an enzymatic reaction?

A

It is transformed into products.

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10
Q

What are enzymes usually made of?

A

Proteins.

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11
Q

What are cofactors?

A

Nonprotein molecules required for some enzymes to function.

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12
Q

What are inorganic cofactors?

A

Metal ions.

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13
Q

What are organic cofactors called?

A

Coenzymes.

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14
Q

Name examples of coenzymes listed in the text.

A

FAD, NAD⁺, and NADP⁺.

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15
Q

Why will some reactions never occur without energy?

A

Because energy is required even if enzymes are present.

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16
Q

What molecule do cells use to manage energy needs?

A

Adenosine triphosphate (ATP).

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17
Q

How can excess energy from reactions be stored?

A

In the bonds of ATP.

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18
Q

How does a cell release energy from ATP?

A

By breaking ATP’s bonds.

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19
Q

When is energy released from ATP?

A

When the terminal phosphate is split from ATP.

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20
Q

What is a metabolic pathway?

A

A set of many coordinated chemical reactions working toward a common goal.

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21
Q

What are the two general types of metabolic pathways?

A

Catabolic and anabolic pathways.

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22
Q

What do catabolic pathways do?

A

Break down macromolecules into simpler components.

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23
Q

What happens to energy during catabolic reactions?

A

Energy is released.

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24
Q

What do catabolic reactions provide for anabolic reactions?

A

Energy.

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25
What do anabolic pathways do?
Build macromolecules by combining simpler molecules.
26
What happens to energy during anabolic reactions?
Energy is used (added).
27
How are catabolic and anabolic pathways linked?
By energy.
28
What is the role of ATP in linking these pathways?
Energy released from catabolism is stored in ATP and used for anabolism.
29
Can microbial metabolism cause disease and food spoilage?
Yes.
30
Are all microbial metabolic pathways harmful?
No, many are beneficial rather than pathogenic.
31
What metabolic process is used in food and beverage production?
Fermentation.
32
Name examples of foods produced using microbial metabolism.
Beer, wine, cheese, yogurt, pickles, sauerkraut, and soy sauce.
33
What organism is mentioned as performing fermentation?
Yeasts such as Saccharomyces cerevisiae.
34
How does the pharmaceutical industry use microbial metabolism?
To produce antibiotics and other treatments.
35
Name antibiotics mentioned that are derived from microbial metabolism.
Penicillin, bacitracin, and erythromycin.
36
Besides antibiotics, what other products come from microbial metabolism?
Vaccines, vitamins, and enzymes.
37
What do enzymes facilitate?
Metabolic reactions.
38
What is ATP used for in cells?
Managing energy needs.
39
What do catabolic reactions couple with?
ATP synthesis.
40
What do anabolic reactions couple with?
ATP breakdown.
41
What is catabolism?
Breakdown of complex molecules
42
What type of chemical process is associated with catabolism?
Hydration
43
What happens to energy during catabolism?
Energy is released
44
What type of reaction is catabolism?
Exergonic reaction
45
What does “ex” mean in exergonic?
Outside
46
What is metabolism?
The sum of all chemical reactions within a living organism.
47
Why can metabolism be viewed as an energy-balancing act?
Because chemical reactions either release energy or require energy.
48
Into what two classes can metabolic reactions be divided?
Reactions that release energy and reactions that require energy.
49
What is catabolism?
The breakdown of complex organic compounds into simpler ones.
50
What type of reactions are catabolic reactions? KNOW
Degradative reactions.
51
What kind of chemical reactions are catabolic reactions usually?
Hydrolytic reactions (use water to break chemical bonds).
52
Are catabolic reactions exergonic or endergonic?
Exergonic (produce more energy than they consume).
53
What is an example of catabolism?
Breakdown of sugars into carbon dioxide and water.
54
What does catabolism provide for the cell?
Energy and building blocks for anabolic reactions.
55
What is anabolism?
The building of complex organic molecules from simpler ones.
56
What are anabolic reactions also called?
Biosynthetic reactions.
57
What type of reactions are anabolic reactions usually?
Dehydration synthesis reactions (release water).
58
Are anabolic reactions exergonic or endergonic?
Endergonic (consume more energy than they produce).
59
Give examples of anabolic processes.
Proteins formed from amino acids Nucleic acids formed from nucleotides Polysaccharides formed from simple sugars
60
What is the purpose of anabolic reactions?
To generate materials for cell growth.
61
What is ATP used for in cells?
To manage energy needs.
62
What are the components of ATP?
Adenine, ribose, and three phosphate groups.
63
What happens when the terminal phosphate is removed from ATP?
ADP is formed and energy is released.
64
How is inorganic phosphate represented?
Pi
65
Write the reaction for ATP breakdown.
ATP → ADP + Pi + energy
66
Write the reaction for ATP synthesis.
ADP + Pi + energy → ATP
67
How are catabolic and anabolic reactions linked?
By energy through ATP.
68
Which reactions are coupled to ATP synthesis?
Catabolic reactions.
69
Which reactions are coupled to ATP breakdown?
Anabolic reactions.
70
Why is ATP important for coupling reactions?
It stores energy from catabolism and releases it to drive anabolism.
71
Is all energy from catabolism available to the cell?
No, some energy is lost as heat.
72
What is a metabolic pathway?
A sequence of chemical reactions in a cell.
73
What determines a cell’s metabolic pathways?
Its enzymes.
74
What determines which enzymes a cell has?
The cell’s genetic makeup.
75
Distinguish catabolism from anabolism.
Catabolism: breaks down molecules, releases energy Anabolism: builds molecules, requires energy
76
How is ATP an intermediate between catabolism and anabolism?
Catabolism stores energy in ATP; anabolism uses energy released from ATP.
77
Do we call microbial metabolism or just metabolism?
We just call it metabolism
78
Distinguish catabolism from anabolism.
Catabolism is the breakdown of complex organic molecules into simpler ones. Catabolic reactions release energy, are generally hydrolytic, and are exergonic (produce more energy than they consume). Anabolism is the building of complex organic molecules from simpler ones Anabolic reactions require energy, often involve dehydration synthesis, and are endergonic (consume more energy than they produce).
79
How is ATP an intermediate between catabolism and anabolism?
Energy released during catabolic reactions is captured and stored in ATP. When ATP is broken down into ADP + Pi, energy is released. This released energy is used to drive anabolic reactions. Therefore, ATP links energy-releasing catabolism with energy-requiring anabolism.
80
What is anabolism?
Synthesize / build
81
What type of chemical process is associated with anabolism?
Dehydration
82
What happens to energy during anabolism?
Uses energy
83
What type of reaction is anabolism?
Endergonic reaction
84
What does “ender” mean in endergonic?
Towards inside
85
What is collision theory
How chemical reactions occur and how certain factors affect the rates of those reactions.
86
When do chemical reactions occur according to collision theory?
When atoms, ions, or molecules collide with sufficient energy and proper orientation.
87
Why don’t all collisions result in a reaction?
Because collisions must have enough energy and the particles must be properly oriented.
88
What is activation energy
The minimum amount of energy required to disrupt a molecule’s stable electronic configuration so a reaction can occur.
89
Why do only some molecules react at a given temperature?
Only a small fraction of molecules possess energy at or above activation energy.
90
What is reaction rate
The frequency of collisions that contain sufficient energy to produce a reaction.
91
How does temperature affect reaction rate?
Increasing temperature increases molecular velocity, collision frequency, and the number of molecules reaching activation energy.
92
How do concentration and pressure affect reaction rate?
Higher concentration or pressure decreases distance between molecules, increasing collision frequency.
93
What is a catalyst
A substance that speeds up a chemical reaction without being permanently altered.
94
What role do enzymes play in cells?
Enzymes act as biological catalysts.
95
What is a substrate?
The specific substance an enzyme acts upon.
96
How do enzymes increase reaction rate?
By lowering activation energy, allowing more molecules to react.
97
Do enzymes increase temperature to speed reactions?
No — enzymes increase reaction rate without raising temperature.
98
What is the active site?
The specific region on the enzyme where the substrate binds.
99
What is an enzyme–substrate complex? Don’t need
A temporary intermediate formed when the substrate binds to the enzyme.
100
What happens to the substrate during enzyme action?
It is rearranged, broken down, or combined with another substrate.
101
What happens to the enzyme after products are released?
The enzyme is unchanged and can be reused.
102
How does an enzyme affect activation energy? Know
It lowers the activation energy required for the reaction.
103
Why do more reactions occur when an enzyme is present?
Because more reactant molecules reach activation energy.
104
What does enzyme specificity mean?
Each enzyme acts on specific substrates and catalyzes only one reaction.
105
Why can enzymes distinguish between similar molecules like starch and cellulose?
Because the orientation of bonds differs, and enzyme active sites are shape-specific.
106
What model explains enzyme specificity?
The lock-and-key model, with induced fit (active site and substrate change shape slightly).
107
Why is enzyme flexibility important?
It allows a tighter fit, increasing reaction efficiency.
108
What is the common molecule between catabolism and anabolism?
ATP
109
What is ATP considered in the cell?
Currency / principal form of energy in any cell
110
How is ATP used in the cell?
Spend, save, exchange
111
How many phosphates does ATP have?
Three phosphates (“P’s”) attached in tandem
112
What type of charge do the phosphate groups have?
Three negative charges
113
What happens when the last phosphate is broken off ATP?
Energy is released
114
What remains after ATP loses its last phosphate? KNOW
ADP + P + Energy
115
What is the first task to maintain life in a cell?
Anabolism
116
What is metabolism?
Metabolism is the sum of all chemical reactions that occur within a cell.
117
What two types of reactions make up metabolism?
Catabolism and anabolism.
118
What is catabolism?
Catabolism is the breakdown of complex molecules into simpler ones, releasing energy.
119
What is anabolism?
Anabolism is the synthesis of complex molecules from simpler ones, requiring energy.
120
How is ATP an intermediate between catabolism and anabolism?
Energy released during catabolic reactions is captured in ATP and then used to drive anabolic reactions.
121
What is collision theory?
Collision theory explains that chemical reactions occur when atoms, ions, or molecules collide with sufficient energy and proper orientation.
122
What is activation energy?
Activation energy is the minimum amount of energy required to initiate a chemical reaction.
123
124
How does temperature affect reaction rate?
Increasing temperature increases molecular motion, collision frequency, and the number of molecules that reach activation energy.
125
How do enzymes affect reaction rate?
Enzymes increase reaction rate by lowering the activation energy without raising temperature.
126
Why are enzymes essential in living systems?
Without enzymes, reactions would require high temperatures that would destroy cellular proteins.
127
What is a catalyst?
A catalyst is a substance that speeds up a chemical reaction without being permanently altered.
128
What role do enzymes play in cells?
Enzymes act as biological catalysts that accelerate biochemical reactions.
129
What is a substrate?
A substrate is the specific molecule an enzyme acts upon.
130
Are enzymes reusable?
Yes, enzymes are unchanged after a reaction and can be reused.
131
What is the active site?
The active site is the specific region on an enzyme where the substrate binds.
132
What is an enzyme–substrate complex? KNOW
When a substrate temporarily binds to an enzyme
133
What happens to the substrate during enzyme action?
The substrate is transformed by rearrangement, breakdown, or combination with another substrate.
134
135
136
Why are enzymes specific?
The three-dimensional shape of the enzyme’s active site fits only particular substrates.
137
What model explains enzyme specificity?
The lock-and-key model, with slight shape adjustment during binding (induced fit).
138
What is an apoenzyme?
The protein portion of an enzyme - not working yet
139
What is a cofactor? KNOW
A nonprotein component required for enzyme activity, often an inorganic ion.
140
What is a coenzyme?
An organic cofactor required for enzyme function.
141
What is a holoenzyme? KNOW
The complete, active enzyme formed when an apoenzyme binds its cofactor.
142
Can an apoenzyme function without a cofactor? KNOW
No, it is inactive without its cofactor.
143
What are oxidoreductases? KNOW
Enzymes that catalyze oxidation–reduction reactions.
144
What do dehydrogenases do? KNOW
They remove hydrogen atoms from substrates.
145
146
What do Metabolic pathways consist of?
Catabolism pathways + anabolism pathways
147
What is an enzyme?
Biological catalyst
148
How do enzymes speed up reactions?
By reducing the chemical requirement needed
149
How do enzymes affect the energy needed to start a reaction? KNOW
They make the required energy go down
150
Are enzymes specific?
Yes, they are specific
151
What key structural feature do enzymes have?
An active site
152
What are enzymes made of?
Proteins
153
What is a Simple enzyme made of?
Protein only
154
What is a conjugated enzyme? Mod
An enzyme that needs a helper molecule
155
What is the protein part of a conjugated enzyme called?
Apoenzyme
156
What completes the enzyme so the active site is functional?
A helper molecule
157
What is a cofactor?
Inorganic helper molecule
158
Give examples of cofactors KNOW
Manganese (Mn⁺), Mg⁺, Ca⁺, Fe⁺
159
What is the role of a cofactor?
Completes the enzyme to complete the active site
160
What is a coenzyme?
Organic helper molecule
161
Give an example of a coenzyme.
Vitamin B
162
Coenzymes are derived from which vitamin?
Vitamin B
163
What is the main role of coenzymes in enzymes?
Complete the active site
164
What do coenzymes pick up during a chemical reaction?
Electrons and protons
165
What do coenzymes become after picking up electrons and protons? KNOW
Electron carriers
166
How do coenzymes carry electrons and protons?
Pick up electrons/protons into their structure
167
What happens to coenzymes after they pick up electrons/protons?
Rearrange their molecules
168
What is added to coenzymes after they pick up electrons/protons?
“Plus”
169
Why are coenzymes important in metabolism?
They become electron carriers (important)
170
What are enzymes made of?
Most enzymes consist of a protein portion called an apoenzyme and a nonprotein component called a cofactor.
171
What is an apoenzyme?
The protein portion of an enzyme that is inactive by itself.
172
What is a cofactor? KNOW
A nonprotein component required to activate an enzyme.
173
What types of substances can act as cofactors? Mod
Metal ions such as iron, zinc, magnesium, or calcium, or organic molecules.
174
What is a coenzyme?
An organic cofactor, often derived from vitamins.
175
What is a holoenzyme?
The complete, active enzyme formed when an apoenzyme binds to its cofactor.
176
What happens if the cofactor is removed from a holoenzyme?
The apoenzyme becomes inactive and the enzyme no longer functions.
177
How can cofactors help catalyze enzymatic reactions?
By forming a bridge between the enzyme and its substrate.
178
179
180
What is the primary role of coenzymes? KNOW
They carry electrons during reactions
181
What is NAD⁺? YES
Nicotinamide adenine dinucleotide, a coenzyme derived from niacin that functions as an electron carrier. NAD is a coenzyme that’s acts as an electron carrier
182
In which type of reactions is NAD⁺ primarily involved?
Catabolic (energy-yielding) reactions.
183
What is NADP⁺?
Nicotinamide adenine dinucleotide phosphate, an electron-carrying coenzyme.
184
In which type of reactions is NADP⁺ primarily involved?
Anabolic (energy-requiring) reactions.
185
What are FMN and FAD?
Flavin coenzymes derived from riboflavin that function as electron carriers.
186
What vitamin are FMN and FAD derived from? KNOW
Riboflavin (vitamin B₂).
187
188
What are oxidoreductases?
Enzymes that catalyze oxidation–reduction reactions.
189
What type of reactions do oxidoreductases participate in?
Reactions involving the transfer of electrons or hydrogen.
190
How many major enzyme classes exist?
Six.
191
192
What do hydrolases do?
Catalyze hydrolysis reactions involving the addition of water.
193
194
195
196
What are the two primary ways enzyme function is regulated in cells?
Control of enzyme synthesis and control of enzyme activity.
197
What does control of enzyme synthesis refer to? KNOW
How much enzyme is produced by the cell.
198
What does control of enzyme activity refer to? KNOW
How active the enzyme is once it is present.
199
What does the N stand for in NADP? KNOW
Nicotinamide
200
What does the A stand for in NADP? KNOW
Adenine
201
What does the D stand for in NADP? KNOW
Dinucleotide
202
What does the P stand for in NADP? KNOW
Phosphate
203
What does the F stand for in FAD? KNOW
Flavin
204
What does the A stand for in FAD?
Adenine
205
What does the D stand for in FAD?
Dinucleotide
206
What are NADP and FAD used for?
Carrying electrons and protons
207
In what cycle are NADP and FAD used to carry electrons and protons? KNOW
Krebs cycle (steps not important)
208
Are the steps of the cycle important to memorize?
No, steps not important
209
What do coenzymes carry within the cycle?
Broken-up parts to the next level in the cycle
210
What is folic acid used for?
DNA synthesis
211
How important is folic acid?
Very important
212
What do enzymes and coenzymes pick up during reactions?
Electrons and protons
213
What do enzymes and coenzymes become after picking them up?
Electron carriers (important)
214
How does temperature affect enzymatic activity?
Enzymes have an optimum temperature where activity is highest
215
What shape does the enzyme activity vs temperature graph follow?
Bell curve
216
What does the peak of the bell curve represent?
Optimum temperature
217
What is the approximate optimum temperature for most cells?
Around 37°C
218
Around what temperature do most human cells operate?
37°C
219
Why does the reaction rate decline steeply to almost zero at high temperatures?
Protein becomes denatured
220
What happens to an enzyme when it is denatured?
It no longer has an active site
221
Why does the reaction rate decline steeply to almost zero at high temperatures?
The enzyme becomes denatured and loses its active site.
222
What are the two primary cellular controls of enzymes?
Control of enzyme synthesis and control of enzyme activity.
223
What does control of enzyme activity refer to?
How much enzyme is present versus how active it is.
224
What major factors influence enzyme activity? KNOW
Temperature, pH, substrate concentration, and the presence or absence of inhibitors.
225
How does temperature affect enzyme activity?
Increasing temperature increases reaction rate up to an optimal temperature.
226
What happens to enzyme activity above the optimal temperature?
The reaction rate drops sharply due to enzyme denaturation.
227
What is the optimal temperature range for most disease-producing bacteria in humans?
Between 35°C and 40°C.
228
What is enzyme denaturation?
The loss of an enzyme’s characteristic three-dimensional (tertiary) structure.
229
What is Denaturation? KNOW
Denaturation breaks hydrogen bonds (not covalent bonds) changing enzyme shape and function
230
Why does denaturation reduce enzyme activity?
The active site loses its shape and can no longer bind the substrate properly.
231
Is enzyme denaturation always irreversible?
No, denaturation can be partially or fully reversible.
232
When does enzyme denaturation become irreversible?
When the enzyme loses solubility and coagulates.
233
What are common causes of enzyme denaturation besides heat? KNOW
- extreme pH - concentrated acids or bases - heavy metals (lead, arsenic, mercury) - alcohol - ultraviolet radiation
234
How does substrate concentration affect enzyme activity? KNOW
Increasing substrate concentration = increases reaction rate Until all enzymes are full
235
What happens when all enzyme active sites are occupied?
The reaction reaches its maximum rate and cannot increase further.
236
How does pH affect enzymatic activity?
Creates a bell curve
237
Where do most cells fall on the pH activity curve?
In the middle of the bell curve
238
What type of pH do most cells prefer?
Neutral pH
239
How does substrate concentration affect enzymatic activity?
Active sites will fill and not be available
240
What happens to enzymatic activity when all active sites are occupied?
Activity becomes a plateau
241
Is the effect of substrate concentration on enzyme activity time dependent?
Yes, time dependent
242
What is the optimum pH of an enzyme
The pH at which an enzyme is most active.
243
What happens to enzyme activity when pH is above or below its optimum?
Enzyme activity and reaction rate decline.
244
Why does changing pH affect enzyme activity?
Changes in H⁺ concentration alter the enzyme’s three-dimensional structure.
245
How can extreme pH changes affect enzymes?
Extreme pH changes can cause enzyme denaturation.
246
How do acids and bases cause enzyme denaturation?
H⁺ and OH⁻ ions compete with hydrogen and ionic bonds in the enzyme, disrupting its structure.
247
What does enzyme saturation mean?
All enzyme active sites are occupied by substrate or product molecules.
248
Under what condition is an enzyme catalyzing a reaction at its maximum rate?
When substrate concentration is extremely high and the enzyme is saturated.
249
Why does increasing substrate concentration beyond saturation not increase reaction rate?
Because all active sites are already in use.
250
Are enzymes usually saturated with substrate under normal cellular conditions?
No, many enzyme molecules are inactive due to lack of substrate.
251
Why does substrate concentration usually influence reaction rate in cells?
Because enzymes are not all being used, so increasing substrate increases reaction rate Until all enzymes are being used
252
What is competitive inhibition?
Inhibitor mimics the real substrate
253
What drug is an example of competitive inhibition?
Sulfur drug
254
What normal substrate does the sulfur drug mimic?
PABA
255
What does PABA stand for?
Para Amino Benzoic Acid
256
PABA is used by bacteria to ___ folic acid *KNOW*
Make folic acid
257
Do humans synthesize folic acid using PABA?
No, humans do not synthesize it this way
258
How do humans obtain folic acid?
As a vitamin in the diet
259
What happens when the sulfur drug replaces PABA? KNOW
Shuts down folic acid synthesis
260
What is the result when sulfur replaces PABA?
Bacterial cell death (cannot synthesize folic acid)
261
Why is sulfur drug used to treat patients?
Because it competes for the normal site of an enzymatic reaction
262
What does the sulfur drug compete with?
PABA
263
Is competitive inhibition described as reversible or irreversible (as written)?
Irreversible
264
What food contains folic acid (as written)?
White bread
265
Do non-competitive inhibitors compete for the active site?
No
266
Where do non-competitive inhibitors bind?
A site that is not the active site
267
How do non-competitive inhibitors affect the enzyme?
Alter the active site
268
What is the name of the site non-competitive inhibitors bind to?
Allosteric site
269
Can non-competitive inhibitors shut down enzymatic activity?
Yes
270
Why is allosteric inhibition useful?
Used by cells to conserve important resources
271
Is non-competitive inhibition reversible (as written)?
Kind of reversible
272
What process uses non-competitive inhibition in small cells? Know
Feedback inhibition
273
What is feedback inhibition? KNOW
Cell stops manufacturing product based on quantity available
274
What molecule stops the enzymatic reaction in feedback inhibition? KNOW
End product
275
How does the end product stop the reaction? KNOW
Binds allosterically
276
What happens when the end product binds allosterically? KNOW
Shuts down the enzymatic reaction
277
When does the enzymatic reaction resume?
When the end product is used up
278
Why do cells use feedback inhibition?
To stop production until excess is used up
279
What are oxidation–reduction reactions also called? KNOW
Redox reactions
280
How many molecules are involved in a redox reaction?
Two molecules
281
Why are redox reactions important?
They are major producers of energy
282
What role do enzymes play in redox reactions?
Enzymes facilitate the reaction
283
What happens between molecule A and molecule B in a redox reaction?
Molecule A gives up something, molecule B receives it
284
What happens to molecule A during the reaction?
A is changed
285
What happens to molecule B during the reaction?
B picks up what A gives up and changes
286
What happens to molecule A during oxidation?
It loses electrons
287
In biological systems, what is commonly lost along with electrons?
Hydrogen atoms
288
What does loss of hydrogen represent? KNOW
Loss of an electron and a proton together
289
What is oxidation also called when hydrogen is lost?
Dehydrogenation
290
What happens to molecule B during reduction?
It gains electrons
291
In biological systems, what does molecule B often gain?
Hydrogen atoms
292
What does gain of hydrogen represent?
Gain of an electron and a proton together
293
What is reduction also called when hydrogen is gained?
Hydrogenation
294
Why is redox often described as hydrogen transfer in metabolism?
Because electrons are usually transferred together with hydrogen atoms
295
What does one hydrogen atom consist of?
One electron and one proton
296
What is happening to substrate molecules during redox reactions? KNOW
They are broken into smaller molecules
297
What does oxidation mean?
Loss of electrons / loss of hydrogen
298
What does reduction mean?
Gain of electrons / gain of hydrogen
299
What are oxidation–reduction reactions also called? KNOW
Redox reactions
300
How many molecules are involved in a redox reaction?
Two molecules
301
Why are redox reactions important?
They are major producers of energy
302
What role do enzymes play in redox reactions?
Enzymes facilitate the reaction
303
What happens between molecule A and molecule B in a redox reaction?
Molecule A gives up something, molecule B receives it
304
What happens to molecule A during the reaction?
A is changed
305
What happens to molecule B during the reaction?
B picks up what A gives up and changes
306
What happens to molecule A during oxidation?
It loses electrons
307
In biological systems, what is commonly lost along with electrons?
Hydrogen atoms
308
What does loss of hydrogen represent?
Loss of an electron and a proton together
309
What is oxidation also called when hydrogen is lost?
Dehydrogenation
310
What happens to molecule B during reduction?
It gains electrons
311
In biological systems, what does molecule B often gain?
Hydrogen atoms
312
What does gain of hydrogen represent?
Gain of an electron and a proton together
313
What is reduction also called when hydrogen is gained?
Hydrogenation
314
Why is redox often described as hydrogen transfer in metabolism? KNOW
Because electrons are usually transferred together with hydrogen atoms
315
What does one hydrogen atom consist of?
One electron and one proton
316
What is happening to substrate molecules during redox reactions?
They are broken into smaller molecules
317
What does oxidation mean? KNOW
Loss of electrons / loss of hydrogen
318
What does reduction mean? KNOW
Gain of electrons / gain of hydrogen
319
What does enzyme saturation mean?
All active sites are occupied, and the enzyme is working at its maximum rate.
320
What happens to reaction rate after enzyme saturation is reached?
Increasing substrate concentration no longer increases the reaction rate.
321
What is a competitive inhibitor?
A molecule that competes with the substrate for the enzyme’s active site.
322
How do competitive inhibitors reduce enzyme activity?
By occupying the active site and preventing substrate binding.
323
What is a noncompetitive inhibitor?
A molecule that binds to a site other than the active site on the enzyme.
324
What is allosteric inhibition?
Noncompetitive inhibition where the inhibitor binds to the allosteric site, changing enzyme shape.
325
What effect does allosteric inhibition have on the enzyme’s active site?
It alters the shape of the active site, making it nonfunctional.
326
Can noncompetitive inhibition be reversible or irreversible?
Yes, depending on whether the enzyme can return to its original shape.
327
How can some chemicals inhibit enzymes that require metal ions?
By binding or tying up the metal ion activators.
328
Why are cyanide and fluoride called enzyme poisons?
They permanently inactivate enzymes by binding essential metal ions.
329
What is feedback inhibition?
The final product of a pathway shuts down an earlier enzyme to prevent overproduction We have enough, stop making more
330
What is another name for feedback inhibition?
End-product inhibition.
331
Which enzyme is usually inhibited during feedback inhibition?
The first enzyme in the metabolic pathway.
332
Why does inhibiting the first enzyme shut down the entire pathway?
Because subsequent substrates are not produced, stopping all downstream reactions.
333
What advantage does feedback inhibition provide to the cell?
Prevents waste of energy and resources by stopping unnecessary synthesis.
334
How does feedback inhibition allow the pathway to resume?
When end-product levels drop, the inhibitor dissociates and enzyme activity resumes.
335
How does sulfanilamide inhibit bacterial growth?
It competes with PABA, preventing folic acid synthesis.
336
Why does sulfanilamide not harm human cells?
Human cells do not use PABA to synthesize folic acid.
337
What is phosphorylation?
The formation of ATP by adding a phosphate (P) to ADP using energy
338
What is the basic phosphorylation equation?
ADP + P + energy → ATP
339
What must be added to ADP to form ATP?
A phosphate (P)
340
Where is most cellular energy produced?
Oxidation–reduction reactions
341
What does it mean when a molecule is oxidized (biological context)?
It has lost a hydrogen (electron + proton)
342
What is the first way cells can trap energy?
Using a substrate willing to give up a phosphate
343
What must a substrate have to trap energy this way?
A phosphate (P) to give up
344
What happens when a substrate gives up a phosphate to ADP?
P + ADP → ATP
345
What is substrate-level phosphorylation? KNOW
ATP made directly - no electron transfer chain Makes ATP directly by giving a phosphate to ADP
346
How is energy first captured in metabolism?
Through oxidation–reduction reactions
347
How is that energy later used to make ATP?
By transferring a phosphate to ADP
348
What is oxidation?
Oxidation is the removal (loss) of electrons from an atom or molecule and often produces energy.
349
What is reduction?
Reduction is the gain of electrons by an atom or molecule.
350
Why are oxidation and reduction reactions always coupled?
Because when one substance loses electrons (oxidation), another must gain them (reduction).
351
What is a redox reaction?
A redox reaction is a paired oxidation–reduction reaction where electrons are transferred from one molecule to another.
352
In a redox reaction, what happens to molecule A and molecule B when an electron is transferred?
Molecule A is oxidized (loses electrons) and molecule B is reduced (gains electrons).
353
In biological systems, why is oxidation often equivalent to dehydrogenation?
Because oxidation usually involves the removal of hydrogen atoms, which contain both an electron and a proton.
354
What is dehydrogenation?
Dehydrogenation is the loss of hydrogen atoms from a molecule and is a common form of biological oxidation.
355
During biological oxidation, what is removed from the organic molecule?
Two hydrogen atoms (equivalent to two electrons and two protons).
356
What coenzyme commonly accepts electrons during biological oxidation?
NAD⁺ (nicotinamide adenine dinucleotide).
357
What happens to NAD⁺ during a redox reaction?
NAD⁺ is reduced by accepting two electrons and one proton to form NADH.
358
What happens to the second proton during NAD⁺ reduction?
One proton (H⁺) is released into the surrounding medium.
359
Why is NADH energy-rich compared to NAD⁺? KNOW
Because NADH carries high-energy electrons
360
What role do redox reactions play in energy production? KNOW
They move electrons so energy can be used to make ATP Redox Reactions = electron transfer that helps make ATP
361
Why is the gain or loss of electrons not always obvious in chemical equations?
Because electrons are not always shown explicitly in biochemical reaction equations.
362
Where is most cellular energy produced?
Oxidation–reduction reactions
363
Is most ATP produced in the electron transport chain (ETC)?
Yes
364
What type of phosphorylation occurs in the electron transport chain (ETC)?
Oxidative phosphorylation
365
What is photophosphorylation?
ATP production using light energy
366
What molecule is required for photophosphorylation?
Chlorophyll
367
Where does photophosphorylation occur?
Only in plants
368
What is oxidation
Oxidation is the loss of electrons from an atom or molecule.
369
What is reduction
Reduction is the gain of electrons by an atom or molecule.
370
Why are oxidation and reduction always coupled?
Because when one substance loses electrons (is oxidized), another must gain them (is reduced).
371
What is a redox reaction?
A reaction involving the transfer of electrons, where oxidation and reduction occur together.
372
In biological systems, oxidation often involves the loss of what?
Hydrogen atoms (dehydrogenation).
373
What role do coenzymes play in oxidation-reduction reactions?
They carry electrons (and hydrogen) from one reaction to another.
374
What happens to NAD⁺ during biological oxidation?
NAD⁺ is reduced to NADH by accepting electrons and hydrogen.
375
Why is NADH considered energy-rich?
Because it contains high-energy electrons that can later be used to generate ATP.
376
Why is glucose such an important molecule for organisms?
Because breaking down glucose releases a lot of energy to make ATP
377
What happens to glucose during cellular respiration?
It is oxidized to CO₂ and H₂O, and its energy is captured in ATP Glucose is broken down to make ATP (energy)
378
What is ATP?
ATP is the cell’s main energy carrier, storing energy in phosphate bonds.
379
What is phosphorylation?
The addition of an inorganic phosphate (Pi) to a molecule, such as ADP forming ATP.
380
What is substrate-level phosphorylation?
ATP is made when a molecule directly gives ADP a phosphate ATP made by direct phosphate transfer
381
Does substrate-level phosphorylation require an electron transport chain?
No.
382
What is oxidative phosphorylation? *KNOW
ATP is made using oxygen and the electron transport chain
383
What molecules initially receive electrons in oxidative phosphorylation?
NAD⁺ and FAD.
384
Where does oxidative phosphorylation occur?
Prokaryotes: plasma membrane Eukaryotes: inner mitochondrial membrane
385
What process uses the energy from electron flow to make ATP?
Chemiosmosis.
386
What is photophosphorylation?
ATP production using light energy in photosynthetic cells.
387
In what type of cells does photophosphorylation occur?
Photosynthetic cells only.
388
What additional energy carrier is produced in photophosphorylation?
NADPH.
389
What is the overall function of metabolic pathways?
To efficiently control chemical reactions by breaking them into stepwise, enzyme-controlled processes.
390
What is the role of redox reactions in energy production?
Breakdown of glucose to release energy
391
Do you need to know the steps of glucose breakdown?
No
392
What do you need to know about glucose breakdown?
Basic breakdown only
393
“Glucose — do on your own”
(As written)
394
What key question explains glucose use in cells?
How do I use glucose to make ATP?
395
How many types of metabolic activity are there?
Three
396
What does aerobic mean?
Oxygen is present
397
What role does oxygen play in aerobic metabolism?
Final electron acceptor
398
How much ATP can be produced from glucose in aerobic metabolism?
Up to 38 ATP (classical microbiology value)
399
Can aerobic metabolism occur in eukaryotes?
Yes (humans)
400
Can aerobic metabolism occur in prokaryotes?
Yes
401
What does anaerobic mean?
No oxygen as the final electron acceptor
402
What metabolic pathways occur in anaerobic metabolism?
Glycolysis and part of the Krebs cycle
403
Is ATP production fixed in anaerobic metabolism?
No, it is variable
404
What determines ATP yield in anaerobic metabolism?
How far the organism can tolerate the pathway
405
Where do electrons go in anaerobic metabolism?
To molecules other than oxygen
406
Are electrons ever transferred to oxygen in anaerobic metabolism?
No
407
What accepts electrons in anaerobic metabolism?
Inorganic molecules (not oxygen)
408
Is fermentation oxygen dependent?
No
409
What metabolic pathway is used in fermentation?
Glycolysis only
410
How much ATP is produced in fermentation?
? (as written)
411
What type of end products are formed in fermentation?
Organic end products
412
What organism produces lactic acid fermentation?
Lactobacillus
413
What organism performs alcohol fermentation?
Yeast
414
What products are formed by yeast fermentation?
Alcohol (beverages) and CO₂
415
Why is CO₂ important in baking?
Leavening
416
oxidation
Oxidation is the removal (loss) of electrons from an atom or molecule.
417
reduction
Reduction is the gain of electrons by an atom or molecule.
418
Why are oxidation and reduction always coupled?
Because when one substance loses electrons (oxidation), another must gain those electrons (reduction).
419
What is a redox reaction?
A redox (oxidation–reduction) reaction is a paired reaction in which one substance is oxidized and another is reduced.
420
In biological systems, oxidation often involves the loss of what?
The loss of hydrogen atoms, which is also called dehydrogenation.
421
Why is glucose considered a highly reduced molecule?
Because it contains many hydrogen atoms, which represent a large amount of potential energy.
422
Why is glucose an important molecule for organisms?
Because its oxidation releases energy that is captured in ATP for cellular work.
423
What is the role of NAD⁺ in biological oxidation?
NAD⁺ accepts electrons and hydrogen, becoming NADH, which stores energy for later ATP production.
424
Why does NADH contain more energy than NAD⁺?
Because NADH carries high-energy electrons removed from organic molecules.
425
How is ATP generated from ADP?
By adding an inorganic phosphate (Pi) to ADP using energy.
426
What is phosphorylation?
Phosphorylation is the addition of a phosphate group to a molecule.
427
How many mechanisms do organisms use to generate ATP?
Three mechanisms.
428
What is substrate-level phosphorylation?
ATP is generated when a high-energy phosphate is directly transferred from a substrate to ADP.
429
What is oxidative phosphorylation?
ATP is generated using energy released as electrons pass through an electron transport chain, ultimately to oxygen or another final electron acceptor.
430
Where does oxidative phosphorylation occur?
Plasma membrane of prokaryotes Inner mitochondrial membrane of eukaryotes
431
What is photophosphorylation?
ATP generation using light energy, occurring only in photosynthetic cells.
432
What molecules are produced during photophosphorylation?
ATP and NADPH
433
What is a metabolic pathway?
A series of enzyme-catalyzed reactions that convert a starting molecule into an end product.
434
Why do cells use metabolic pathways instead of releasing energy all at once?
To release energy gradually, preventing heat damage and allowing energy to be captured efficiently.
435
What role do redox reactions play in metabolic pathways?
They allow energy to be transferred stepwise and stored in molecules like ATP and NADH.
436
Why are enzymes important in metabolic pathways?
Each step is catalyzed by a specific enzyme, allowing precise control of reactions.
437
What are CO₂ and H₂O in metabolic pathways?
Secondary products (by-products or waste products) of energy-producing reactions.
438
What is oxidation?
Oxidation is the loss of electrons (e⁻) from an atom or molecule.
439
What is reduction?
Reduction is the gain of electrons (e⁻) by an atom or molecule.
440
Why are oxidation and reduction always coupled?
When one substance loses electrons (is oxidized), another must gain those electrons (is reduced).
441
What is a redox reaction?
A redox reaction is a paired oxidation–reduction reaction involving electron transfer.
442
In biological systems, oxidation often involves the loss of what?
The loss of hydrogen atoms (dehydrogenation).
443
What role does NAD⁺ play in redox reactions?
NAD⁺ acts as an electron (and hydrogen) carrier, accepting electrons during oxidation reactions.
444
What happens when NAD⁺ is reduced?
NAD⁺ accepts two electrons and one proton and becomes NADH.
445
Why is NADH important?
NADH is energy-rich and can be used later to generate ATP.
446
What is phosphorylation?
Phosphorylation is the addition of an inorganic phosphate (Pi) to a molecule.
447
How is ATP formed from ADP?
Energy is used to add Pi to ADP, forming ATP.
448
What is substrate-level phosphorylation?
ATP is formed when a high-energy phosphate is transferred directly from a substrate to ADP.
449
What is oxidative phosphorylation?
ATP is produced using energy released from electrons moving through the electron transport chain, coupled to chemiosmosis.
450
Where does oxidative phosphorylation occur?
Plasma membrane in prokaryotes; Inner mitochondrial membrane in eukaryotes.
451
What is photophosphorylation?
ATP generation using light energy during photosynthesis.
452
What is a metabolic pathway?
A sequence of enzyme-catalyzed reactions that converts a starting material into an end product.
453
Why are metabolic pathways stepwise instead of releasing energy all at once?
Controlled steps prevent energy loss as heat and allow energy to be captured as ATP.
454
What is the primary carbohydrate used by cells for energy?
Glucose.
455
What are the two main processes used to extract energy from glucose?
Cellular respiration and fermentation.
456
What are the three main stages of cellular respiration?
Glycolysis; Krebs cycle; Electron transport chain.
457
What happens during glycolysis?
Glucose is oxidized to pyruvic acid, producing some ATP and NADH.
458
What happens during the Krebs cycle?
Acetyl-CoA is oxidized to CO₂, producing NADH, FADH₂, and some ATP.
459
What happens during the electron transport chain?
NADH and FADH₂ donate electrons that drive ATP production; most ATP is made here.
460
How does fermentation differ from respiration?
Fermentation has no Krebs cycle or electron transport chain.
461
Where does ATP come from in fermentation?
Only from glycolysis.
462
Why is ATP yield lower in fermentation?
Because only glycolysis produces ATP.
463
How many ATP can a bacterium produce from complete oxidation of one glucose molecule?
38 ATP.
464
What is oxidation?
Oxidation is the loss of electrons (e⁻) from an atom or molecule.
465
What is reduction?
Reduction is the gain of electrons (e⁻) by an atom or molecule.
466
Why are oxidation and reduction always coupled?
When one substance loses electrons (is oxidized), another must gain those electrons (is reduced).
467
What is a redox reaction?
A redox reaction is a paired oxidation–reduction reaction involving electron transfer.
468
In biological systems, oxidation often involves the loss of what?
The loss of hydrogen atoms (dehydrogenation).
469
What role does NAD⁺ play in redox reactions?
NAD⁺ acts as an electron (and hydrogen) carrier, accepting electrons during oxidation reactions.
470
What happens when NAD⁺ is reduced?
NAD⁺ accepts two electrons and one proton and becomes NADH.
471
Why is NADH important?
NADH is energy-rich and can be used later to generate ATP.
472
What is phosphorylation?
Phosphorylation is the addition of an inorganic phosphate (Pi) to a molecule.
473
How is ATP formed from ADP?
Energy is used to add Pi to ADP, forming ATP.
474
What is substrate-level phosphorylation?
ATP is formed when a high-energy phosphate is transferred directly from a substrate to ADP.
475
What is oxidative phosphorylation?
ATP is produced using energy released from electrons moving through the electron transport chain, coupled to chemiosmosis.
476
Where does oxidative phosphorylation occur?
Plasma membrane in prokaryotes; Inner mitochondrial membrane in eukaryotes.
477
What is photophosphorylation?
ATP generation using light energy during photosynthesis.
478
What is a metabolic pathway?
A sequence of enzyme-catalyzed reactions that converts a starting material into an end product.
479
Why are metabolic pathways stepwise instead of releasing energy all at once?
Controlled steps prevent energy loss as heat and allow energy to be captured as ATP.
480
What is the primary carbohydrate used by cells for energy?
Glucose.
481
What are the two main processes used to extract energy from glucose?
Cellular respiration and fermentation.
482
What are the three main stages of cellular respiration?
Glycolysis; Krebs cycle; Electron transport chain.
483
What happens during glycolysis?
Glucose is oxidized to pyruvic acid, producing some ATP and NADH.
484
What happens during the Krebs cycle?
Acetyl-CoA is oxidized to CO₂, producing NADH, FADH₂, and some ATP.
485
What happens during the electron transport chain?
NADH and FADH₂ donate electrons that drive ATP production; most ATP is made here.
486
How does fermentation differ from respiration?
Fermentation has no Krebs cycle or electron transport chain.
487
Where does ATP come from in fermentation?
Only from glycolysis.
488
Why is ATP yield lower in fermentation?
Because only glycolysis produces ATP.
489
How many ATP can a bacterium produce from complete oxidation of one glucose molecule?
38 ATP.
490
What is oxidation?
Oxidation is the loss of electrons (e⁻) from an atom or molecule.
491
What is reduction?
Reduction is the gain of electrons (e⁻) by an atom or molecule.
492
Why are oxidation and reduction always coupled?
When one substance loses electrons (is oxidized), another must gain those electrons (is reduced).
493
What is a redox reaction?
A redox reaction is a paired oxidation–reduction reaction involving electron transfer.
494
In biological systems, oxidation often involves the loss of what?
The loss of hydrogen atoms (dehydrogenation).
495
What role does NAD⁺ play in redox reactions?
NAD⁺ acts as an electron (and hydrogen) carrier, accepting electrons during oxidation reactions.
496
What happens when NAD⁺ is reduced?
NAD⁺ accepts two electrons and one proton and becomes NADH.
497
Why is NADH important?
NADH is energy-rich and can be used later to generate ATP.
498
What is phosphorylation?
Phosphorylation is the addition of an inorganic phosphate (Pi) to a molecule.
499
How is ATP formed from ADP?
Energy is used to add Pi to ADP, forming ATP.
500
What is substrate-level phosphorylation?
ATP is formed when a high-energy phosphate is transferred directly from a substrate to ADP.
501
What is oxidative phosphorylation?
ATP is produced using energy released from electrons moving through the electron transport chain, coupled to chemiosmosis.
502
Where does oxidative phosphorylation occur?
Plasma membrane in prokaryotes; Inner mitochondrial membrane in eukaryotes.
503
What is photophosphorylation?
ATP generation using light energy during photosynthesis.
504
What is a metabolic pathway?
A sequence of enzyme-catalyzed reactions that converts a starting material into an end product.
505
Why are metabolic pathways stepwise instead of releasing energy all at once?
Controlled steps prevent energy loss as heat and allow energy to be captured as ATP.
506
What is the primary carbohydrate used by cells for energy?
Glucose.
507
What are the two main processes used to extract energy from glucose?
Cellular respiration and fermentation.
508
What are the three main stages of cellular respiration?
Glycolysis; Krebs cycle; Electron transport chain.
509
What happens during glycolysis?
Glucose is oxidized to pyruvic acid, producing some ATP and NADH.
510
What happens during the Krebs cycle?
Acetyl-CoA is oxidized to CO₂, producing NADH, FADH₂, and some ATP.
511
What happens during the electron transport chain?
NADH and FADH₂ donate electrons that drive ATP production; most ATP is made here.
512
How does fermentation differ from respiration?
Fermentation has no Krebs cycle or electron transport chain.
513
Where does ATP come from in fermentation?
Only from glycolysis.
514
Why is ATP yield lower in fermentation?
Because only glycolysis produces ATP.
515
How many ATP can a bacterium produce from complete oxidation of one glucose molecule?
38 ATP.
516
What is another name for glycolysis?
Embden–Meyerhof pathway
517
How many stages does glycolysis have?
Two stages: a preparatory stage and an energy-conserving stage
518
What happens during the preparatory stage of glycolysis?
Two ATP are used to phosphorylate, restructure, and split one six-carbon glucose into two three-carbon molecules
519
What two three-carbon molecules are produced when glucose is split in glycolysis?
Glyceraldehyde-3-phosphate (GP) and dihydroxyacetone phosphate (DHAP)
520
What happens to DHAP during glycolysis?
DHAP is readily converted to glyceraldehyde-3-phosphate (GP)
521
After DHAP is converted, how many GP molecules continue through glycolysis?
Two GP molecules
522
What happens during the energy-conserving stage of glycolysis?
Two three-carbon molecules are oxidized to two molecules of pyruvic acid
523
During the energy-conserving stage, what happens to NAD⁺?
NAD⁺ is reduced to NADH
524
How many ATP molecules are formed during the energy-conserving stage?
Four ATP by substrate-level phosphorylation
525
What is the net ATP gain from glycolysis per glucose molecule?
Two ATP
526
What are the two major alternative pathways to glycolysis in bacteria?
The pentose phosphate pathway and the Entner–Doudoroff pathway
527
What is another name for the pentose phosphate pathway?
Hexose monophosphate shunt
528
Does the pentose phosphate pathway operate independently of glycolysis?
No, it operates simultaneously with glycolysis
529
What types of sugars are broken down by the pentose phosphate pathway?
Five-carbon sugars (pentoses) and glucose
530
What important intermediates are produced by the pentose phosphate pathway?
Pentoses used for nucleic acid synthesis, photosynthesis, and certain amino acids
531
What reduced coenzyme is produced by the pentose phosphate pathway?
NADPH from NADP⁺
532
What is the net ATP yield of the pentose phosphate pathway per glucose?
One ATP
533
Does the pentose phosphate pathway occur in human cells?
Yes
534
How many ATP are produced per glucose in the Entner–Doudoroff pathway?
One ATP
535
What reduced coenzymes are produced in the Entner–Doudoroff pathway?
One NADPH and one NADH
536
Can bacteria using the Entner–Doudoroff pathway metabolize glucose without glycolysis?
Yes
537
Is the Entner–Doudoroff pathway common in gram-positive bacteria?
No, it is generally not found in gram-positive bacteria
538
In what types of organisms is the Entner–Doudoroff pathway found?
Some gram-negative bacteria, archaea, algae, and plants
539
Why is the Entner–Doudoroff pathway clinically important?
It is sometimes used to identify Pseudomonas in clinical laboratories
540
Compare ATP yield per glucose: glycolysis vs pentose phosphate vs Entner–Doudoroff
Glycolysis: 2 ATP (net) Pentose phosphate: 1 ATP Entner–Doudoroff: 1 ATP
541
What is cellular respiration?
An ATP-generating process in which molecules are oxidized and the final electron acceptor comes from outside the cell
542
What essential system operates during cellular respiration?
The electron transport chain
543
What distinguishes aerobic from anaerobic respiration?
The final electron acceptor
544
What is the final electron acceptor in aerobic respiration?
O₂
545
What is the final electron acceptor in anaerobic respiration?
An inorganic molecule other than O₂ (rarely organic)
546
After glycolysis, pyruvic acid can enter which two pathways?
Cellular respiration or fermentation
547
What defines cellular respiration?
An ATP-generating process in which molecules are oxidized and electrons are transferred to an external inorganic electron acceptor via an electron transport chain.
548
What is the difference between aerobic and anaerobic respiration?
Aerobic respiration uses O₂ as the final electron acceptor; anaerobic respiration uses an inorganic molecule other than O₂.
549
What is the role of the Krebs cycle?
To oxidize acetyl-CoA and transfer high-energy electrons to NAD⁺ and FAD, forming NADH and FADH₂.
550
What are the main products of the Krebs cycle?
CO₂, NADH, FADH₂, and a small amount of ATP.
551
Where is most ATP generated during respiration?
In the electron transport chain.
552
How many ATP can a bacterium produce from complete oxidation of one glucose molecule?
38 ATP.
553
Why does fermentation produce much less ATP than respiration?
Fermentation lacks the Krebs cycle and electron transport chain, so ATP is produced only by glycolysis.
554
What is cellular respiration?
An ATP-generating process in which molecules are oxidized and the final electron acceptor comes from outside the cell (usually an inorganic molecule).
555
What is the essential feature that distinguishes respiration from fermentation?
The operation of an electron transport chain.
556
What is the final electron acceptor in aerobic respiration?
Oxygen (O₂).
557
What is the final electron acceptor in anaerobic respiration?
An inorganic molecule other than O₂ (rarely an organic molecule).
558
What are the three main stages of glucose respiration?
Glycolysis, Krebs cycle, and electron transport chain.
559
During which stage of respiration is most ATP produced?
The electron transport chain.
560
Why are NADH and FADH₂ important products of the Krebs cycle?
They contain most of the energy originally stored in glucose and deliver it to the electron transport chain.
561
How many ATP molecules can a bacterium produce from complete oxidation of one glucose molecule?
38 ATP.
562
glycolysis
Glycolysis is the oxidation of glucose to pyruvic acid and is the first stage of carbohydrate catabolism.
563
Does glycolysis require oxygen?
No. Glycolysis can occur whether oxygen is present or not.
564
What are the main products of glycolysis (per glucose)?
2 pyruvic acid, 2 NADH, and a net gain of 2 ATP.
565
How is ATP produced in glycolysis?
By substrate-level phosphorylation.
566
What is the main role of the Krebs cycle?
To oxidize acetyl CoA and transfer energy to electron carriers (NADH and FADH₂).
567
What are the main products of the Krebs cycle (per glucose)?
CO₂, NADH, FADH₂, and 2 ATP (or GTP).
568
Is the Krebs cycle a major ATP-producing stage?
No. Its primary role is producing reduced coenzymes, not ATP.
569
What is the electron transport chain?
A series of oxidation–reduction reactions that transfer electrons and use released energy to generate ATP.
570
What is the main purpose of the electron transport chain?
To produce most of the ATP during cellular respiration.
571
Which molecules donate electrons to the ETC?
NADH and FADH₂.
572
What is the final electron acceptor in aerobic respiration?
Oxygen (O₂).
573
What is oxidation?
Loss of electrons.
574
What is reduction?
Gain of electrons.
575
Why are redox reactions important in metabolism?
They transfer energy through the movement of electrons.
576
What is the role of NAD⁺ and FAD in metabolism?
They act as electron carriers.
577
What happens when NAD⁺ and FAD are reduced?
They become NADH and FADH₂ and carry high-energy electrons.
578
How many ATP are produced directly in glycolysis?
2 ATP (net).
579
How many ATP are produced directly in the Krebs cycle?
2 ATP (or GTP).
580
Where is most ATP generated during glucose metabolism?
In the electron transport chain.
581
What is aerobic respiration?
ATP-generating metabolism that uses oxygen as the final electron acceptor.
582
What is anaerobic respiration?
Respiration that does not use oxygen and uses another inorganic molecule as the final electron acceptor.
583
What is fermentation?
An energy-yielding process that does not use an electron transport chain and regenerates NAD⁺.
584
How does the electron transport chain contribute to ATP production?
The electron transport chain uses energy released from redox reactions to generate most of the ATP during cellular respiration.
585
What is the role of redox reactions in the electron transport chain?
Redox reactions transfer electrons and release energy that is used to produce ATP.
586
Why does the electron transport chain produce most of the ATP from glucose?
Because it captures energy from electron transfers and uses it to generate large amounts of ATP.
587
What provides the energy used to make ATP during the electron transport chain?
Energy released as electrons are transferred through the electron transport chain.
588
What is the role of the electron transport chain in aerobic respiration?
It transfers electrons through redox reactions and generates most of the ATP produced during aerobic respiration.
589
What is the final electron acceptor in aerobic respiration?
Oxygen (O₂).
590
Approximately how many ATP molecules are produced by the electron transport chain per glucose molecule in aerobic respiration?
About 34 ATP.
591
How many total ATP are produced per glucose molecule in aerobic respiration in prokaryotes?
38 ATP.
592
How many total ATP are produced per glucose molecule in aerobic respiration in eukaryotes?
36 ATP.
593
Why do eukaryotes produce fewer ATP than prokaryotes during aerobic respiration?
Because NADH produced in the cytoplasm must be transported into mitochondria, causing some energy loss.
594
How do carrier molecules function in the electron transport chain?
They accept and donate electrons, transferring energy through redox reactions that lead to ATP production.
595
What are the principal products of the Krebs cycle?
CO₂, NADH, FADH₂, and ATP.
596
How do aerobic and anaerobic respiration differ in their final electron acceptor?
Aerobic respiration uses oxygen, while anaerobic respiration uses an inorganic molecule other than oxygen.
597
Why does anaerobic respiration produce less ATP than aerobic respiration?
Because only part of the Krebs cycle and electron transport chain operate under anaerobic conditions.
598
What is fermentation?
A process that releases energy from organic molecules without oxygen, without the Krebs cycle or an electron transport chain, using an organic molecule as the final electron acceptor.
599
What is the main purpose of fermentation?
To regenerate NAD⁺ so glycolysis can continue.
600
What is metabolism?
The sum of all chemical reactions occurring in a cell or organism.
601
What role do enzymes play in metabolism?
Enzymes facilitate (speed up) metabolic reactions.
602
What is ATP and why is it important?
ATP is the energy currency of the cell; it is used by microbes and other cells to manage energy needs.
603
How are catabolic reactions related to ATP?
Catabolic reactions break down molecules and are coupled with ATP synthesis (ATP production).
604
How are anabolic reactions related to ATP?
Anabolic reactions build complex molecules and are coupled with ATP breakdown (ATP use).
605
How does microbial metabolism benefit the pharmaceutical industry?
Microbes (bacteria and fungi) are used to produce antibiotics (e.g., penicillin from Penicillium fungus), vaccines, vitamins, and enzymes.
606
What is penicillin, and where does it come from?
Penicillin is an antibiotic derived from the fungus Penicillium.
607
How is microbial metabolism used in sewage treatment?
Bacteria (including some cyanobacteria) break down harmful organic matter in contaminated water.
608
Why are microbes important in sewage treatment facilities?
They carry out biological processes that remove organic waste and pollutants.
609
What metabolic process is used to produce foods and beverages like beer, wine, cheese, and yogurt?
Fermentation (a catabolic process).
610
Which microorganism is commonly used in fermentation of alcoholic beverages?
Yeast, such as Saccharomyces cerevisiae.
611
Why is microbial metabolism crucial to food production?
It enables fermentation, preservation, flavor development, and production of many foods.
612
catabolism
Metabolic pathways that break down macromolecules into simpler molecules.
613
What happens to energy during catabolic reactions?
Energy is released.
614
What type of molecules are produced by catabolic pathways?
Simpler molecules.
615
anabolism
Metabolic pathways that build macromolecules by combining simpler molecules.
616
What happens to energy during anabolic reactions?
Energy is required (added).
617
What type of molecules are produced by anabolic pathways?
Macromolecules.
618
Which type of pathway releases energy: catabolic or anabolic?
Catabolic.
619
Which type of pathway requires energy: catabolic or anabolic?
Anabolic.
620
How are catabolic and anabolic pathways connected?
By energy.
621
What do catabolic reactions provide for anabolic reactions?
The energy needed to drive them.
622
How is energy transferred between catabolism and anabolism?
Through ATP.
623
What happens to energy released during catabolism?
It is stored in ATP.
624
What happens when ATP is used in anabolic reactions?
Energy is released from ATP to build macromolecules.
625
Catabolism: break down or build up?
Break down.
626
Anabolism: break down or build up?
Build up.
627
Catabolism = energy _______; Anabolism = energy _______.
Released; required.
628
Which pathways are directly linked in a cycle through ATP?
Catabolic and anabolic pathways.
629
What is metabolism?
The sum of catabolic and anabolic reactions in a cell.
630
What is catabolism?
Provides energy and building blocks for anabolism.
631
What is anabolism?
Uses energy and building blocks to build large molecules.
632
What are the fundamental differences between anabolism and catabolism?
Catabolism releases energy and building blocks Anabolism uses energy and building blocks to build molecules
633
What is the role of ATP?
ATP provides energy for cellular processes.
634
What does catabolism do?
Releases energy by oxidation of molecules.
635
What happens to glucose during catabolism?
Glucose is oxidized to CO₂ and H₂O.
636
How is energy released from ATP?
Energy is released by hydrolysis of ATP.
637
What happens to ADP and Pi in energy storage?
Energy is used to form ATP from ADP + Pi.
638
Where is energy stored in the cell?
Energy is stored in molecules of ATP.
639
What does anabolism do?
Uses energy to synthesize macromolecules that make up the cell.
640
What are proteins broken down into?
Amino acids.
641
What is the relationship between catabolism and anabolism?
Catabolism releases energy that is used to drive anabolism through ATP.
642
What happens if a reaction results in excess energy?
Some energy can be captured in the form of ATP’s bonds.
643
How can a cell use the energy stored in ATP?
The cell breaks ATP’s bonds and uses the released energy to fuel other reactions.
644
What molecule makes up the base of ATP?
Adenosine.
645
How many phosphates are attached to ATP?
Three phosphates.
646
When is energy released from ATP?
When the terminal phosphate is split from ATP.
647
What are enzymes?
Biological catalysts.
648
Are enzymes specific or general in their action?
Specific for a chemical reaction.
649
Are enzymes used up during a reaction?
No, they are not used up.
650
What are enzymes made up of?
An apoenzyme and a cofactor.
651
What is an apoenzyme?
The protein portion of an enzyme.
652
What is a cofactor?
The nonprotein component of an enzyme.
653
What is a coenzyme?
An organic cofactor.
654
What is a holoenzyme?
Apoenzyme plus cofactor.
655
What enzyme component is the protein portion?
Apoenzyme
656
What enzyme component is the nonprotein portion?
Cofactor
657
What is a coenzyme?
An organic cofactor
658
What is a holoenzyme?
Apoenzyme + cofactor (whole enzyme, active)
659
Is an apoenzyme active or inactive by itself?
Inactive
660
What happens when a coenzyme binds to an apoenzyme?
A holoenzyme is formed and becomes active
661
NAD⁺ derived from
Niacin (vitamin B₃)
662
NAD stands for
Nicotinamide adenine dinucleotide
663
NAD⁺ used for
Electron carrier in catabolic (energy-releasing) reactions
664
NADP⁺ derived from
Niacin (vitamin B₃)
665
NADP stands for
Nicotinamide adenine dinucleotide phosphate
666
NADP⁺ used for
Electron carrier in anabolic (biosynthetic) reactions
667
FAD derived from
Riboflavin (vitamin B₂)
668
FAD stands for
Flavin adenine dinucleotide
669
FAD used for
Electron carrier in metabolic reactions
670
FMN derived from
Riboflavin (vitamin B₂)
671
FMN stands for
Flavin mononucleotide
672
FMN used for
Electron carrier in metabolic reactions
673
coenzyme A derived from
Pantothenic acid (vitamin B₅)
674
Coenzyme A stands for
Coenzyme A (A = acetyl)
675
coenzyme A used for
Transfers acetyl (carbon) groups in metabolism
676
What factors influence Enzyme Activity
Temp, pH, substrate concentration, inhibitors
677
How does temperature affect enzymatic activity at low to moderate temperatures?
Enzymatic activity increases as temperature increases.
678
What happens to enzyme activity after it reaches an optimal temperature?
Enzyme activity decreases sharply.
679
Why does enzyme activity decrease at high temperatures?
The enzyme protein is denatured by heat and becomes inactivated.
680
What happens to the reaction rate when an enzyme is denatured?
The reaction rate falls steeply.
681
How does pH affect enzymatic activity?
Enzymatic activity varies depending on pH.
682
At what pH is the enzyme illustrated most active?
Around pH 5.0.
683
What happens to enzyme activity when pH moves away from the optimal value?
Enzymatic activity decreases.
684
Does enzymatic activity increase indefinitely as pH changes?
No, it increases up to an optimal pH and then decreases.
685
How does substrate concentration affect enzymatic activity?
Increasing substrate concentration increases the rate of reaction.
686
Why does enzymatic activity increase as substrate concentration increases?
More substrate molecules are available to bind to enzyme active sites.
687
What happens when all enzyme active sites are filled?
The maximum rate of reaction is reached.
688
Does enzymatic activity continue to increase once all active sites are occupied?
No, the reaction rate levels off at a maximum.
689
What is oxidation?
Removal of electrons.
690
What is reduction?
Gain of electrons.
691
In an oxidation–reduction reaction, what happens to electrons?
Electrons are transferred from one substance to another.
692
If substance A loses an electron, what happens to A?
A is oxidized.
693
If substance B gains an electron, what happens to B?
B is reduced.
694
In a redox reaction, can oxidation occur without reduction?
No, oxidation and reduction occur together.
695
In biological systems, with what are electrons often associated?
Hydrogen atoms.
696
What form do biological oxidations often take?
Dehydrogenations.
697
What does dehydrogenation mean in the context of redox reactions?
Removal of hydrogen atoms (and their associated electrons).
698
What is the basic mechanism by which ATP is generated?
Phosphorylation (addition of P) of ADP.
699
What molecule is phosphorylated to form ATP?
ADP.
700
What components are required to convert ADP into ATP?
ADP + energy + inorganic phosphate (P).
701
How does the structure of ATP differ from ADP?
ATP has three phosphate groups; ADP has two.
702
What molecule is present in both ADP and ATP?
Adenosine.
703
What happens to energy during the formation of ATP?
Energy is stored in ATP.
704
What is substrate-level phosphorylation?
ATP generation from the transfer of a high-energy phosphate to ADP.
705
In substrate-level phosphorylation, where does the phosphate come from?
A phosphorylated substrate (high-energy phosphate).
706
What molecule receives the phosphate during substrate-level phosphorylation?
ADP.
707
What are the products of substrate-level phosphorylation?
ATP and a dephosphorylated substrate.
708
What role does the enzyme play in substrate-level phosphorylation?
It transfers the phosphate from the substrate to ADP.
709
What happens to the substrate after phosphate transfer?
It becomes the substrate without the phosphate group.
710
What is oxidative phosphorylation?
ATP generation using energy released from the transfer of electrons.
711
What does oxidation refer to in oxidative phosphorylation?
Loss of electrons from one compound.
712
What does reduction refer to in oxidative phosphorylation?
Gain of electrons by another compound.
713
Where is ATP generated during oxidative phosphorylation?
In the electron transport chain.
714
What happens to the organic molecule during oxidation?
It becomes an oxidized organic molecule.
715
What coenzyme acts as the electron carrier in this process (as shown)?
NAD⁺.
716
What is formed when NAD⁺ gains electrons and protons?
NADH + H⁺ (reduced electron carrier).
717
In biological systems, electrons are commonly transferred with what atom?
Hydrogen (H).
718
What type of biological reaction is oxidative phosphorylation based on?
Oxidation–reduction (redox) reactions.
719
What is photophosphorylation?
ATP generation driven by light-energized electron transfer.
720
What causes chlorophyll to give up electrons?
Light.
721
What happens to chlorophyll when it gives up electrons?
It is oxidized.
722
Where does the energy used to generate ATP come from in photophosphorylation?
From the transfer of electrons.
723
Through what do electrons move after leaving chlorophyll?
A system of carrier molecules.
724
What is the final result of electron transfer in photophosphorylation?
ATP is generated.
725
What type of reaction provides energy for ATP formation in photophosphorylation?
Oxidation of chlorophyll.
726
What is glycolysis?
The breakdown of glucose to pyruvic acid.
727
What molecule is broken down during glycolysis?
Glucose.
728
What is the end product of glycolysis?
Pyruvic acid.
729
What energy molecule is produced during glycolysis?
ATP.
730
What electron carrier is produced during glycolysis?
NADH.
731
Glycolysis produces which two important molecules?
ATP and NADH.
732
Glycolysis converts glucose into what while producing ATP and NADH?
Pyruvic acid.
733
What is the purpose of the preparatory stage of glycolysis?
To prepare glucose for breakdown.
734
Does the preparatory stage of glycolysis require energy or produce energy?
It requires energy.
735
How many ATP are used in the preparatory stage of glycolysis?
2 ATP.
736
During which steps is ATP used in the preparatory stage of glycolysis?
Steps 1 and 3.
737
Why is ATP used in the preparatory stage of glycolysis?
To prepare glucose for breakdown.
738
How many total steps are involved in preparing glucose for breakdown in glycolysis?
10 steps.
739
Is the preparatory stage focused on splitting glucose or preparing it?
Preparing it.
740
What is the purpose of the energy-conserving stage of glycolysis?
To produce energy.
741
How many ATP are produced in the energy-conserving stage of glycolysis?
4 ATP.
742
During which steps is ATP produced in the energy-conserving stage of glycolysis?
Steps 7 and 10.
743
How many NADH are produced in the energy-conserving stage of glycolysis?
2 NADH.
744
During which step is NADH produced in glycolysis?
Step 6.
745
Is ATP consumed or produced in the energy-conserving stage of glycolysis?
Produced.
746
What is the final product of glycolysis shown at the end of the energy-conserving stage?
Pyruvic acid (pyruvate).
747
What is the purpose of the intermediate step?
To convert pyruvic acid into acetyl CoA so it can enter the Krebs cycle.
748
What molecule enters the intermediate step?
Pyruvic acid (from glycolysis).
749
What molecule is produced at the end of the intermediate step?
Acetyl CoA.
750
What happens to pyruvic acid during the intermediate step?
It is oxidized and decarboxylated.
751
What is released when pyruvic acid is decarboxylated?
CO₂.
752
Which electron carrier is produced during the intermediate step?
NADH.
753
Which molecule is reduced to form NADH in the intermediate step?
NAD⁺.
754
Is ATP produced during the intermediate step?
No.
755
Why is Coenzyme A (CoA) important in the intermediate step?
It binds to the acetyl group to form acetyl CoA.
756
What is the purpose of the Krebs cycle?
To extract high-energy electrons from acetyl CoA and transfer them to electron carriers.
757
What molecule enters the Krebs cycle?
Acetyl CoA.
758
Where does acetyl CoA come from?
From the intermediate step (pyruvate oxidation).
759
What are the main products of the Krebs cycle?
NADH, FADH₂, ATP, and CO₂.
760
Which electron carriers are produced in the Krebs cycle?
NADH and FADH₂.
761
Why are NADH and FADH₂ important?
They carry high-energy electrons to the electron transport chain.
762
Is ATP produced directly in the Krebs cycle?
Yes, a small amount (via substrate-level phosphorylation).
763
What happens to carbon during the Krebs cycle?
Carbon is released as CO₂.
764
Does the Krebs cycle require oxygen directly?
No, but it depends on oxygen indirectly because NADH and FADH₂ must be recycled by the electron transport chain.
765
What is regenerated at the end of the Krebs cycle to keep it going?
Oxaloacetic acid.
766
What is the electron transport chain (ETC)?
A series of carrier molecules that are oxidized and reduced as electrons are passed down the chain.
767
What is the main purpose of the electron transport chain?
To use energy from electrons to produce ATP.
768
Which molecules donate electrons to the electron transport chain?
NADH and FADH₂.
769
What happens to NADH and FADH₂ when they donate electrons?
They are oxidized to NAD⁺ and FAD.
770
Name the main carrier molecules in the electron transport chain.
FMN, Q (ubiquinone), and cytochromes.
771
What happens to energy as electrons move down the electron transport chain?
Energy is released in small steps.
772
How is the energy released from the electron transport chain used?
To produce ATP by chemiosmosis.
773
What process links the electron transport chain to ATP synthesis?
Chemiosmosis.
774
Does the electron transport chain produce ATP directly?
No — it produces a proton gradient that drives ATP synthesis.
775
Where does the electron transport chain occur in eukaryotic cells?
The inner mitochondrial membrane.
776
Where does glycolysis occur in eukaryotic cells?
Cytoplasm
777
Where does glycolysis occur in prokaryotic cells?
Cytoplasm
778
Where does the intermediate step occur in eukaryotic cells?
Cytoplasm
779
Where does the intermediate step occur in prokaryotic cells?
Cytoplasm
780
Where does the Krebs cycle occur in eukaryotic cells?
Mitochondrial matrix
781
Where does the Krebs cycle occur in prokaryotic cells?
Cytoplasm
782
Where does the electron transport chain (ETC) occur in eukaryotic cells?
Mitochondrial inner membrane
783
Where does the electron transport chain (ETC) occur in prokaryotic cells?
Plasma membrane
784
What is the key difference in location of cellular respiration between prokaryotes and eukaryotes?
Eukaryotes use mitochondria; prokaryotes carry out all steps in the cytoplasm or plasma membrane.
785
What is aerobic respiration in prokaryotes?
The final electron acceptor in the electron transport chain is molecular oxygen (O₂).
786
What is the final electron acceptor in aerobic respiration?
Molecular oxygen (O₂).
787
What is anaerobic respiration in prokaryotes?
The final electron acceptor in the electron transport chain is not O₂.
788
Why does anaerobic respiration yield less energy than aerobic respiration?
Because only part of the Krebs cycle operates under anaerobic conditions.
789
What is fermentation in prokaryotes?
Uses an organic molecule as the final electron acceptor.
790
Does fermentation use the Krebs cycle or the electron transport chain?
No, it does not use the Krebs cycle or ETC.
791
What is the key difference between aerobic respiration, anaerobic respiration, and fermentation in prokaryotes?
Aerobic: final electron acceptor is O₂ Anaerobic: final electron acceptor is not O₂ Fermentation: uses an organic molecule and does not use Krebs cycle or ETC
792
What electron acceptor produces NO₂⁻, N₂, and H₂O in anaerobic respiration?
NO₃⁻
793
What are the products when NO₃⁻ is used as an electron acceptor?
NO₂⁻, N₂ + H₂O
794
What electron acceptor produces H₂S and H₂O in anaerobic respiration?
SO₄²⁻
795
What are the products when SO₄²⁻ is used as an electron acceptor?
H₂S + H₂O
796
What electron acceptor produces CH₄ and H₂O in anaerobic respiration?
CO₃²⁻
797
What are the products when CO₃²⁻ is used as an electron acceptor?
CH₄ + H₂O
798
Match the electron acceptor to its products in anaerobic respiration.
NO₃⁻ → NO₂⁻, N₂ + H₂O SO₄²⁻ → H₂S + H₂O CO₃²⁻ → CH₄ + H₂O
799
What process breaks glucose down to pyruvic acid in fermentation?
Glycolysis
800
How many ATP are produced during glycolysis in fermentation?
2 ATP
801
How many ADP are converted to ATP during glycolysis?
2 ADP → 2 ATP
802
What molecule is produced at the end of glycolysis before fermentation begins?
2 pyruvic acid
803
What molecule (or derivative) is used to form fermentation end-products?
Pyruvic acid (or derivative)
804
What happens to NADH during the formation of fermentation end-products?
2 NADH → 2 NAD⁺
805
Why is NAD⁺ regenerated during fermentation (based on the diagram)?
NADH is converted back to NAD⁺ during formation of fermentation end-products
806
Outline the sequence shown in the fermentation overview diagram.
Glucose → Glycolysis → 2 pyruvic acid → Formation of fermentation end-products
807
What process always occurs before fermentation begins?
Glycolysis
808
What molecule is produced at the end of glycolysis and enters fermentation pathways?
Pyruvic acid
809
What are the two types of fermentation shown on this slide?
Lactic acid fermentation Alcohol fermentation
810
What is the end-product of lactic acid fermentation?
Lactic acid
811
What happens to NADH during lactic acid fermentation?
NADH is oxidized to NAD⁺
812
What are the end-products of alcohol fermentation?
Ethanol and CO₂
813
What intermediate molecule is formed during alcohol fermentation before ethanol is produced?
Acetaldehyde
814
What happens to NADH during alcohol fermentation?
NADH is oxidized to NAD⁺
815
Which fermentation pathway releases CO₂?
Alcohol fermentation
816
What is the purpose of fermentation shown in this diagram?
To regenerate NAD⁺ so glycolysis can continue
Microbiology
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