1
Q
What type of respiration is fermentation classified as?
A
Anaerobic
2
Q
Where does fermentation occur in the cell?
A
cytoplasm
3
Q
What type of oxidation occurs during fermentation?
A
Partial oxidation
4
Q
What are the major end products of fermentation? Enumerate.
A
Acids: lactic acid, acetic acid, butyric acid, acetone
Alcohols: ethanol, isopropyl alcohol
Gases: CO₂, H₂
Contaminants
5
Q
What three factors influence the specific end products of fermentation?
(T,O,E)
A
- Type of organism
- Original substrate
- Enzymes present and active
6
Q
What is the ATP yield of lactic acid fermentation
A
2 ATP
7
Q
What are the end products of lactic acid fermentation?
A
Lactic acid
8
Q
Give two examples of genera that perform lactic acid fermentation.
A
Streptococcus and Lactobacillus
9
Q
What are some food-related consequences of lactic acid fermentation?
A
Food spoilage
Food production (yogurt, pickles, milk, cucumbers, sauerkraut, cabbage)
10
Q
Distinguish between homolactic and heterolactic fermenters
A
Homolactic fermenters use the glycolytic pathway and directly reduce almost all their pyruvate to lactate with lactate dehydrogenase.
Heterolactic fermenters form substantial amounts of products other than lactate, producing lactate, ethanol, and CO₂ via the phosphoketolase pathway.
11
Q
What is the ATP yield of alcohol fermentation?
A
2 ATP
12
Q
What are the end products of alcohol fermentation?
A
Alcohol (ethanol) and CO₂
13
Q
Give one organism used in alcohol fermentation and its uses.
A
Saccharomyces cerevisiae (yeast)
Used in alcoholic beverage production and bread dough rising.
14
Q
What are the two types of formic acid fermentation?
A
- Mixed-acid fermentation
- Butanediol fermentation
15
Q
A
16
Q
What is the ATP yield of propionic acid fermentation?
A
2 ATP
17
Q
What are the end products of propionic acid fermentation?
A
Propionic acid and CO₂
18
Q
What organism performs propionic acid fermentation?
A
Propionibacterium species
19
Q
What is the main product of butyric acid fermentation?
A
Butyric acid (sometimes with acetone)
20
Q
Which organism performs butyric acid fermentation?
A
Clostridium acetobutylicum
21
Q
A
22
Q
What are the end products of mixed-acid fermentation?
A
(4 acids and alcohol)
Acetic acid, lactic acid, succinic acid, formic acid, and ethyl alcohol
23
Q
Name four organisms that perform mixed-acid fermentation.
A
Escherichia coli, Enterobacter, Salmonella, Proteus
24
Q
Describe the process of butanediol fermentation
A
Pyruvate is converted to acetoin.
Acetoin is reduced to 2,3-butanediol with NADH.
End products: ethanol and smaller amounts of acids (also found in mixed-acid fermentation).
25
Name organisms that use butanediol fermentation
Enterobacter, Serratia, Erwinia, and some Bacillus species.
26
What is butylene-glycol fermentation?
Fermentation producing *2,3-butyleneglycol*, e.g., by *Pseudomonas.*
27
**Identify the fermentation type with:**
End product: lactic acid
Organisms: Streptococcus, Lactobacillus
ATP yield: 2
Lactic acid fermentation
28
**Identify the fermentation type with:**
End product: ethanol + CO₂
Organism: Saccharomyces cerevisiae
Application: Bread dough rising and alcoholic beverages
Alcohol fermentation
29
Identify the fermentation type with:
End product: propionic acid + CO₂
Organism: Propionibacterium
Propionic acid fermentation
30
Identify the fermentation type with:
End product: butyric acid + acetone
Organism: Clostridium acetobutylicum
Butyric acid fermentation
31
Identify the fermentation type with:
End products: acetic acid, lactic acid, succinic acid, formic acid, ethanol
Organisms: E. coli, Enterobacter, Salmonella, Proteus
Mixed-acid fermentation
32
Identify the fermentation type with:
Process: pyruvate → acetoin → 2,3-butanediol
Organisms: Enterobacter, Serratia, Erwinia, Bacillus
Butanediol fermentation
33
What is the main end product of homolactic fermentation?
Lactic acid
34
Name one model organism that performs homolactic fermentation
Lactobacillus
35
What is the pathway homolactic fermenters use to reduce pyruvate?
The glycolytic pathway with lactate dehydrogenase, which converts pyruvate directly into lactate
36
What are the end products of mixed acid fermentation? Enumerate.
Lactate, acetate, formate, and succinate.
37
Why is mixed acid fermentation important in microbiology?
It is useful for differentiating and identifying members of the Enterobacteriaceae.
38
What are the end products of butyric acid fermentation
Butyric acid and acetone (sometimes with butanol as well).
39
Which organism is the classic model for butyric acid fermentation?
Clostridium acetobutylicum
40
What industrial application is linked to Clostridium acetobutylicum?
Production of solvents like acetone, butanol, and ethanol (ABE fermentation).
41
What is a common food application of propionic acid fermentation?
It is used in Swiss cheese production (creates the characteristic flavor and CO₂ "holes").
42
series of interconnected biochemical reactions that occur within a cell, allowing organisms to convert nutrients into energy and building blocks for cellular processes
microbial metabolism
43
A series of enzyme-catalyzed reactions that convert substrates into products.
metabolic pathways
44
Differentiate catabolic and anabolic pathways.
Catabolic pathways: Systematic breakdown of complicated molecules into simpler ones, releasing energy (stored in ATP).
Anabolic pathways: Synthesis of complex molecules from simpler ones, requiring energy (often from ATP generated during catabolism).
45
Complex molecules are broken down into simpler ones, releasing chemical bond energy that is captured as ATP.
catabolic pathways
46
A catabolic pathway that converts glucose into two molecules of pyruvate, producing ATP and NADH.
glycolysis
47
It is the initial step in both aerobic and anaerobic respiration and provides intermediates for other metabolic pathways.
glycolysis
48
What is the Krebs cycle (citric acid cycle)?
catabolic pathway that oxidizes acetyl-CoA to produce NADH, FADH₂, ATP, and releases CO₂.
49
Why is the Krebs cycle considered central to aerobic respiration?
provides high-energy electrons for the electron transport chain
50
What is the electron transport chain (ETC)
catabolic pathway that produces ATP through transfer of electrons from NADH and FADH₂ to 》 oxygen
51
Why is the electron transport chain crucial for aerobic organisms?
the major source of ATP in aerobic organisms and crucial for energy production
52
The breakdown of fatty acids into acetyl-CoA units for energy production.
beta-oxidation
53
When does beta-oxidation become especially important?
prolonged exercise or fasting, when fats are a major energy source.
54
What is protein catabolism?
Degradation of proteins into amino acids for energy and other uses.
55
It allows proteins to be used for energy and integrated into central metabolic pathways.
protein catabolism
56
Processes that synthesize complex molecules from simpler ones, requiring an input of energy.
Anabolic Pathways
57
Where does the energy for anabolic pathways usually come from?
From ATP generated during catabolic processes.
58
An anaerobic process that converts sugars into 》 acids, gases, or alcohol, allowing ATP production without oxygen.
fermentation
59
Give two examples of fermentation.
Lactic acid fermentation and alcoholic fermentation.
60
What is metabolic regulation?
Mechanisms that control the rate of metabolic pathways.
61
A type of regulation where the end product of a pathway inhibits an earlier step.
feedback inhibition
62
A type of regulation where molecules bind to enzymes to alter their activity.
allosteric regulation
63
Metabolic pathways of organisms (e.g., plants, some bacteria) that use inorganic substances like carbon dioxide as a carbon source, using light or chemical energy to drive processes.
autotrophic metabolisms
64
What are the two types of autotrophic metabolism?
Photosynthesis: Converts light energy into chemical energy stored in glucose.
Chemosynthesis: Converts inorganic molecules into organic molecules using chemical energy.
65
Converts inorganic molecules into organic molecules using chemical energy.
Chemosynthesis
66
Pathways in organisms that obtain energy and carbon from organic compounds, relying on consuming other organisms or organic matter.
heterotrophic metabolisms
67
What processes fall under heterotrophic metabolism?
*Respiration* (aerobic with oxygen, anaerobic without oxygen) and, *fermentation.*
68
Pathways that function both catabolically and anabolically.
Amphibolic Pathways
69
Give two of the most important amphibolic pathways
Glycolytic pathway
Tricarboxylic acid (TCA) cycle
70
A metabolic process in which cells convert biochemical energy from nutrients into ATP, using oxygen as the final electron acceptor.
aerobic respiration
71
A type of cellular respiration that occurs without oxygen, where other molecules such as sulfate, nitrate, or carbon dioxide act as the final electron acceptors.
anaerobic respiration
72
Enumerate the various types of prokaryotic energy production processes
(F A A L P A M)
Fermentation
Anaerobic respiration
Aerobic respiration
Lithotrophy
Photoheterotrophy
Anoxygenic photosynthesis
Methanogenesis
73
Protein catalysts that speed up and direct chemical reactions.
enzymes
74
Because they increase the rate of a chemical reaction without being permanently altered themselves.
enzymes as catalysts
75
What is the specificity of enzymes?
have great specificity for the reaction catalyzed and the molecules acted on
76
What are substrates?
Reacting molecules in enzyme-catalyzed reactions.
77
What are products?
Substances formed in enzyme-catalyzed reactions
78
How are most enzymes named?
adding “-ase” to the substrate they act on.
79
Give examples of substrate-based enzyme names.
Lipase (acts on lipids)
DNase (acts on DNA)
Protease (acts on proteins)
80
Name enzymes based on function:
➝
Removes hydrogen → Dehydrogenase
Removes phosphate → Phosphatase
81
Enzymes can also be grouped **based on type of reaction they catalyze.**
Give two groups.
Oxidoreductases → catalyze oxidation & reduction reactions
Hydrolases → catalyze hydrolysis reactions
82
What are the two main structural forms of enzymes?
➝ Protein enzymes and ribozymes (RNA enzymes, e.g., ribosome).
83
List the characteristic functions of enzymes
Presence of an active site
Specificity
Modified forms (inactive vs. active)
Requirement of coenzyme or cofactor
84
What is the role of the active site in enzymes?
region where the substrate binds and the reaction occurs.
85
What is a coenzyme/cofactor?
non-protein compound required for enzyme activity.
86
How do enzymes catalyze reactions?
lowering the activation energy of the reaction.
87
Without enzymes, would reactions still occur?
Yes, but at a very slow rate.
88
What is the Induced-Fit Model of enzymes?
model where the enzyme changes shape slightly to better fit the substrate upon binding.
89
What are the structural components of enzymes?
Apoenzyme (protein portion)
Allosteric site
Cofactor
Coenzyme
90
Give examples of coenzymes.
Vitamins such as CoA, NAD, NADP, FAD, FMN
91
Give examples of metal ions used as cofactors.
Cu, Zn, Mg, Fe, Ca, Co, Mn
92
What are the two main parts of an enzyme?
Apoenzyme (protein part) and Cofactor (non-protein part).
93
The protein part of the enzyme, inactive by itself.
apoenzyme
94
non-protein part, usually a metal ion, that turns the apoenzyme on.
cofactor
95
organic cofactor is?
coenzyme
96
The whole active enzyme, formed by apoenzyme + cofactor.
holoenzyme
97
What role do metal ion cofactors play in enzymatic reactions?
They form a bridge between the enzyme and substrate to facilitate the reaction.
98
Is an enzyme active without a cofactor?
No, enzymes are inactive without cofactors
99
What is Niacin’s coenzyme form?
NAD (Nicotinamide adenine dinucleotide)
100
What is Riboflavin’s coenzyme form?
FAD (Flavin adenine dinucleotide)
101
What is Pantothenic acid’s coenzyme form?
Coenzyme A
102
Name the two most important coenzymes.
NAD⁺ and NADP⁺
103
Differentiate NAD⁺ and NADP⁺ based on function.
➝
NAD⁺: Carries electrons in catabolic reactions.
NADP⁺: Carries electrons in anabolic reactions.
104
What vitamin are both NAD⁺ and NADP⁺ derived from?
The B vitamin nicotinic acid
105
What is the role of NAD as an electron carrier?
transfers electrons during metabolic reactions.
106
List five factors that affect enzyme activity.
Temperature, pH, acids/bases, UV light, concentration of substrates (saturation), and inhibitors.
107
How does temperature affect enzyme activity?
Increasing temperature increases reaction rate until denaturation occurs.
108
The temperature at which the enzyme catalyzes the reaction at its maximum rate.
optimal temperature
109
Why does denaturation stop enzyme activity
Enzymes are polypeptides that only function when folded properly. Unfolding disrupts active site shape.
110
What factors can cause denaturation?
Changes in temperature, pH, or salt concentration (which disrupt amino acid R-group interactions).
111
What is the importance of optimal pH for enzymes?
It favors the native conformation (correct folding)
112
What happens if the pH is too acidic or too basic?
enzyme becomes denatured
113
How does substrate concentration affect enzyme activity?
Increasing substrate concentration increases reaction rate until saturation.
114
When all active sites are occupied, the enzyme is working at maximum speed.
saturation
115
What is the **maximum turnover number** of an enzyme?
The top speed at which an enzyme converts substrate into product.
116
Does adding more substrate beyond saturation increase reaction rate?
No, because the enzyme is already working at maximum capacity.
117
Molecules that affect enzymatic activity.
enzyme inhibitors
118
What are the two main classes of enzyme inhibitors?
Competitive inhibitors and noncompetitive inhibitors.
119
Where do competitive inhibitors bind?
the enzyme’s active site.
120
Why can competitive inhibitors bind the active site?
They have a similar shape to the substrate.
121
What are the two types of binding for competitive inhibitors?
Irreversible and reversible
122
Where do noncompetitive inhibitors bind?
allosteric site
123
How do noncompetitive inhibitors affect enzyme activity?
They change the enzyme’s shape, preventing proper substrate binding.
124
Summarize the two ways inhibitors bind enzymes.
➝
Competitive inhibition: Binding to active site.
Allosteric (noncompetitive) inhibition: Binding elsewhere, changing enzyme shape.
125
How can inhibitors bind to enzymes in terms of reversibility?
➝ They can bind reversibly (come off) or irreversibly (do not come off, e.g., poisons).
126
Which antibiotic acts as a competitive inhibitor by binding to the active site of the enzyme involved in the synthesis of the pentaglycine crossbridge in bacterial cell walls?
Penicillin
127
Which competitive inhibitor blocks the active site of the enzyme that converts para-aminobenzoic acid (PABA) into folic acid?
Sulfanilamide (Sulfa drugs)
128
Why is folic acid essential for microorganisms?
Folic acid is required for the synthesis of DNA and RNA.
129
What type of enzyme inhibition is characterized by the inhibitor binding to an allosteric site?
Noncompetitive inhibition
130
List the four properties that can describe enzyme inhibition.
1. Excitatory
2. Inhibitory
3. Reversible
4. Irreversible
131
What role do the end-products of metabolic pathways play in enzyme regulation?
They act as **reversible enzyme inhibitors** through *feedback inhibition*
132
How does feedback inhibition regulate a metabolic pathway?
end-product inhibits the first enzyme in the pathway, turning the pathway “off"
133
Define oxidation and reduction in biological systems.
Oxidation → Loss of hydrogens and/or electrons
Reduction → Gain of hydrogens and/or electrons
134
What is the primary energy source oxidized by microorganisms?
Carbohydrates, with glucose being the most common energy source.
135
List the two major processes by which energy is obtained from glucose.
1. Respiration
2. Fermentation
136
is an ATP-generating process in which molecules are oxidized and the final electron acceptor is almost always an inorganic molecule.
Respiration
137
How do bacterial cells generate energy via respiration?
By oxidizing organic molecules through a series of biochemical reactions to produce ATP.
138
What are the two types of respiration and their final electron acceptors?
1. Aerobic respiration → Oxygen is the final electron acceptor
2. Anaerobic respiration → A different exogenous acceptor (often inorganic, sometimes organic like fumarate)
139
Give at least five possible final electron acceptors in anaerobic respiration.
NO₃⁻
SO₄²⁻
CO₂
Fe³⁺
SeO₄²⁻
(fumarate may also be used – organic acceptor)
140
What is the origin of the word fermentation?
From Latin fermentare, meaning "to cause to rise or ferment."
141
What happens to the energy substrate in fermentation?
The energy substrate is oxidized and degraded without the participation of an exogenous (external) electron acceptor.
142
How is redox balance achieved in fermentation?
Organic compounds both donate and accept electrons, so balance is achieved without the need for external electron acceptors.
143
Name the three major pathways microorganisms use to degrade sugars to pyruvate.
1. Glycolysis
2. Pentose phosphate pathway
3. Entner-Doudoroff pathway
144
Carbohydrates and other nutrients serve two main functions in the metabolism of heterotrophic microorganisms.
What are they?
1. They are oxidized to release energy
2. They supply carbon or building blocks for the synthesis of new cell constituents
145
What are the four subpathways of aerobic cellular respiration?
1. Glycolysis
2. Transition reaction
3. Kreb’s cycle
4. Electron transport system
146
What is substrate-level phosphorylation?
A phosphate group is directly transferred from a high-energy substrate molecule to ADP, forming ATP, during specific enzymatic reactions in metabolic pathways.
147
Which metabolic pathways involve substrate-level phosphorylation?
Glycolysis and Kreb’s cycle
148
What is oxidative phosphorylation?
Electrons are transported through the electron transport chain (ETC), releasing energy that is used to pump protons across the membrane, creating a proton gradient (proton motive force, PMF).
149
What is **photophosphorylation** and where does it occur?
Photophosphorylation = ATP formation through a series of sunlight-driven reactions.
Occurs in the light-dependent reactions of photosynthesis, where light excites electrons and they move through protein complexes in the photosynthetic ETC.
150
Why is ATP considered central in metabolism?
ATP is at the center of a cell’s energy cycle, regardless of whether the organism is heterotrophic, photosynthetic, or chemoautotrophic.
151
What role does ATP expenditure play in cellular processes?
The expenditure of ATP **powers all processes** that are part of cellular work.
152
is a series of reactions (Krebs cycle and respiratory chain) that converts glucose to CO₂, produces H₂O, uses oxygen as the final electron acceptor, and generates a relatively large amount of ATP
Aerobic Respiration
153
Which groups of organisms typically use aerobic respiration?
Many bacteria, fungi, protozoa, and animals.
154
What is the primary central pathway of glucose catabolism in all living organisms?
Glycolysis
(Embden-Meyerhof-Parnas Pathway)
155
Where does glycolysis occur in prokaryotes and eukaryotes, and does it require oxygen?
It occurs in the cytoplasmic matrix of both prokaryotes and eukaryotes and does not require oxygen
156
List the major characteristics of glycolysis.
- Starts from a six-carbon glucose molecule.
- Produces a three-carbon pyruvate as the end product.
Pyruvate has three different possible metabolic destinations.
- Catalyzed by enzymes.
- Requires investment of 2 ATP and produces 4 ATP (net yield = 2 ATP per glucose).
- Generates NADH.
Uses substrate-level phosphorylation for ATP synthesis.
157
What is the net ATP yield from glycolysis per glucose molecule?
Net yield = 2 ATP per glucose
158
How does the ATP and NADH yield differ between the six-carbon stage and the three-carbon stage of glycolysis?
**Six-carbon stage**: 2 ATP are invested to form fructose-1,6-bisphosphate.
**Three-carbon stage** (each glyceraldehyde-3-phosphate → pyruvate): produces 1 NADH + 2 ATP.
Since two glyceraldehyde-3-phosphates arise from one glucose, the **total yield of the three-carbon stage** = 4 ATP + 2 NADH per glucose.
*Net result after subtracting invested ATP* = 2 ATP and 2 NADH per glucose.
159
What alternative pathway can function alongside glycolysis or Entner-Doudoroff, either aerobically or anaerobically?
The Pentose Phosphate Pathway
(also called phosphoketolase pathway or hexose monophosphate pathway)
160
What is the dual role of the pentose phosphate pathway?
It is important in both biosynthesis and catabolism
161
What are the specific products and functions provided by the pentose phosphate pathway?
Provides NADPH as a source of electrons.
Produces a 4-carbon sugar (for aromatic amino acid synthesis).
Produces a 5-carbon sugar (for nucleic acid synthesis and CO₂ acceptor).
162
163
Basahin niyo nalang ito
🔋 Phosphorylation (How ATP is Made)
ATP can be produced by three different methods:
1. **Substrate-level phosphorylation**
Direct transfer of a phosphate group from a high-energy substrate to ADP → ATP.
Occurs in: glycolysis and Krebs cycle.
2. **Oxidative phosphorylation**
Electrons pass through the electron transport chain (ETC).
Energy from electron transfer pumps protons (H⁺) across a membrane → builds a proton motive force (PMF).
Protons flow back through ATP synthase → ATP produced.
Main ATP producer in respiration.
3. **Photophosphorylation**
Specific to photosynthesis.
Light energy excites electrons, which pass through a photosynthetic ETC.
Proton motive force is generated → ATP formed.
164
Also called: Embden–Meyerhof–Parnas pathway.
Where it happens: Cytoplasm (both prokaryotes and eukaryotes).
Oxygen requirement: None (anaerobic process, though it can feed into aerobic respiration).
Steps:
Starts with a 6-carbon glucose molecule.
Ends with two 3-carbon pyruvate molecules.
Catalyzed by enzymes.
ATP use and gain:
Investment: 2 ATP used.
Payoff: 4 ATP produced (via substrate-level phosphorylation).
Net gain: 2 ATP per glucose.
NADH produced: 2 NADH per glucose (used later in respiration for more ATP).
⚙️ Detailed ATP and NADH Yield
Six-carbon stage (energy investment phase):
2 ATP are consumed to phosphorylate glucose into fructose-1,6-bisphosphate.
Three-carbon stage (energy payoff phase):
Each glyceraldehyde-3-phosphate (2 per glucose) produces:
1 NADH
2 ATP
Since there are 2 glyceraldehyde-3-phosphate molecules: total = 2 NADH + 4 ATP.
Final calculation:
Total produced: 4 ATP, 2 NADH.
Subtract 2 ATP used → Net yield = 2 ATP + 2 NADH per glucose.
Glycolysis
165
Also called:
Phosphoketolase pathway
Hexose monophosphate pathway
Key Features:
Alternative to glycolysis (can work alongside glycolysis or the ED pathway).
Can operate aerobically or anaerobically.
Involved in both catabolism (breakdown for energy) and biosynthesis (building molecules).
Major Roles:
1. Provides NADPH → source of electrons for anabolic reactions (e.g., fatty acid, nucleotide, and amino acid synthesis).
2. Generates 4-carbon sugars → used in aromatic amino acid synthesis.
3. Generates 5-carbon sugars → used in nucleic acid synthesis (DNA & RNA).
4. Produces CO₂ acceptors needed for biosynthesis.
✅ Summary: PPP is less about ATP generation and more about making reducing power (NADPH) and precursor molecules for biosynthesis.
Pentose phosphate pathway
166
Key Features:
Location: Cytoplasm.
Works anaerobically.
Uses different enzymes than glycolysis or PPP.
Found in: Pseudomonas, Zymomonas, Enterococcus, Rhizobium, Agrobacterium.
The Entner–Doudoroff Pathway (ED)
167
Process:
1. Starts the same way as PPP → glucose → glucose-6-phosphate → 6-phosphogluconate.
2. Instead of full oxidation, 6-phosphogluconate is dehydrated into KDPG (2-keto-3-deoxy-6-phosphogluconate).
3. KDPG is cleaved by KDPG aldolase → produces:
1 pyruvate
1 glyceraldehyde-3-phosphate (G3P)
4. G3P enters the lower half of glycolysis → converted into another pyruvate.
End Products per Glucose:
1 ATP (net yield → much less than glycolysis)
1 NADPH (used in biosynthesis, similar to PPP)
1 NADH (used in ETC for ATP generation if respiration occurs)
2 pyruvate molecules
H₂O
✅ Summary: The ED pathway is an alternative to glycolysis used by certain microbes. It produces less ATP (only 1 net ATP per glucose) but also makes NADPH, giving it biosynthetic importance.
Entner–Doudoroff Pathway (ED)
168
Once glucose is degraded into pyruvate, it can be further oxidized in aerobic respiration.
Requires oxygen as the final electron acceptor.
Uses the TCA cycle (Tricarboxylic Acid Cycle) = Citric Acid Cycle = Krebs Cycle.
Carbohydrate Catabolism: Pyruvate → CO₂ (via Krebs Cycle)
169
Main Function:
Fully oxidize pyruvate (via Acetyl-CoA) into CO₂.
Produce NADH and FADH₂ → electron carriers that fuel the Electron Transport Chain (ETC).
Provide carbon skeletons (intermediates) for biosynthesis (amino acids, nucleotides, etc.).
Carbohydrate Catabolism: Pyruvate → CO₂ (via Krebs Cycle)
170
Location:
Eukaryotes → mitochondria.
Prokaryotes → cytoplasm.
Start: Each pyruvate (3C) is converted into Acetyl-CoA (2C) before entering the cycle.
Cycle: Begins and ends with oxaloacetic acid (4C).
Krebs Cycle
171
For each Acetyl-CoA (per turn of cycle):
2 CO₂ released
3 NADH produced
1 FADH₂ produced
1 ATP (via substrate-level phosphorylation, actually GTP in some organisms)
CoA regenerated
Oxaloacetate regenerated (to continue the cycle)
Krebs Cycle
172
Krebs Cycle: Total Yield (per glucose)?
Since 1 glucose → 2 pyruvate → 2 Acetyl-CoA, the cycle turns twice per glucose.
2 ATP (or GTP)
6 NADH
2 FADH₂
4 CO₂
173
Oxidation in Krebs Cycle?
Pyruvate is completely oxidized to CO₂.
Energy is conserved in the form of NADH and FADH₂, which carry high-energy electrons to the ETC for oxidative phosphorylation.
174
Function of the Krebs Cycle:
•Extract energy from acetyl-CoA (derived from pyruvate).
•Generate reduced cofactors (NADH, FADH₂) which carry electrons to the electron transport chain (ETC).
•Provide carbon skeletons for biosynthesis (precursors for amino acids, nucleotides, etc.).
175
A cyclic series of reactions where acetyl-CoA (2C) combines with oxaloacetate (4C) to form citrate (6C), which is then broken down back to oxaloacetate.
Krebs Cycle (TCA / Citric Acid Cycle)
176
Per 1 Acetyl-CoA molecule oxidized:
2 CO₂ released (decarboxylation).
3 NADH produced.
1 FADH₂ produced.
1 ATP (or GTP) produced via substrate-level phosphorylation.
**Regenerates:**
CoA (for reuse)
Oxaloacetate (cycle continues)
177
Per glucose molecule (2 acetyl-CoA enter cycle):
4 CO₂
6 NADH
2 FADH₂
2 ATP
178
A sequence of electron carriers in the inner mitochondrial membrane (eukaryotes) or the plasma membrane (prokaryotes).
Transfers electrons from donors (NADH, FADH₂) to O₂ (the final electron acceptor).
The Respiratory Chain: Electron Transport Chain (ETC)
179
Process:
1. NADH and FADH₂ donate electrons.
2. Electrons move through carrier complexes (I-IV).
3. This movement pumps protons (H⁺) across the membrane, creating a proton motive force (PMF).
4. ATP synthase uses this PMF to synthesize ATP.
Electron Transport Chain (ETC)
180
Electron Transport Chain (ETC)
ATP yield from electron carriers:
NADH → ~3 ATP
FADH₂ → ~2 ATP
This process is called oxidative phosphorylation.
181
When O₂ is not available, organisms use ---
fermentation or anaerobic respiration.
182
Examples of anaerobic end-products by bacteria:
Lactic acid → Lactobacillus
Mixed acids → Enterobacteriaceae
Butanediol → Klebsiella, Enterobacter
Butyric acid → Clostridia
Butanol-acetone → Clostridia
Propionic acid → Corynebacteria
183
Anaerobic process in the cytoplasm.
Only partial oxidation of glucose.
Produces small amounts of ATP (2 ATP per glucose) via substrate-level phosphorylation.
Uses organic intermediaries (not O₂) as final electron acceptors.
Fermentation
184
Fermentation General Features:
Anaerobic
**Cytoplasm** location
Partial oxidation
End-products depend on:
1. Type of organism
2. Original substrate
3. Enzymes available
185
Fermentation Common End Products:
Acids: Lactic acid, acetic acid, butyric acid, acetone
Alcohols: Ethanol, isopropanol
Gases: CO₂, H₂
Contaminants (depends on microbial growth environment).
186
Define respiration
It is an ATP-generating process in which
**molecules are oxidized**, and the **final electron acceptor** is
almost always an **inorganic molecule**. In other words,
**microorganisms break down organic molecules,** transfer
their electrons through a series of reactions, and produce
ATP.
Respiration is a metabolic process by which bacterial cells
generate energy (ATP) by oxidizing organic molecules
through biochemical pathways.
**Respiration can be divided into two types:**
1. Aerobic respiration – the final electron acceptor is
oxygen (O₂).
2. Anaerobic respiration – the final electron acceptor
is a different exogenous molecule that is not
oxygen. Most of the time, this acceptor is inorganic,
such as nitrate (NO₃⁻), sulfate (SO₄²⁻), carbon
dioxide (CO₂), ferric iron (Fe³⁺), or selenate (SeO₄²⁻).
In some cases, an organic molecule like fumarate
may also serve as the electron acceptor.
187
Fermentation process
the energy substrate (such as glucose) is oxidized and degraded **without the participation of an external electron acceptor.** Instead, the process is self-contained: organic compounds within the cell donate electrons and also accept electrons.
This way, redox balance is achieved without using oxygen or other external molecules.
Fermentation is considered a form of anaerobic catabolism.
While it generates less ATP compared to respiration, it is
still essential for many microorganisms that live in oxygenlimited environments.
188
Pathways for Degrading Sugars to Pyruvate
Microorganisms degrade glucose and other sugars into
pyruvate (or similar intermediates) through three primary
routes:
1. Glycolysis (Embden-Meyerhof-Parnas pathway)
2. Pentose Phosphate Pathway
3. Entner-Doudoroff Pathway
Microbiology
flashcards
Decks in class (22)
# Cards
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Module 6106
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Module 7181
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Module 8. 1132
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Module 8.2115
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Module 8.3283
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Module 9188
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9191
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11.1191
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11.2170
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Module 11.2160
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Module 12 (Slide 1 To 39)94
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Module 12 (Slide 40 To 65)76
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Module 12 (66-101)156
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Module 12 (-110 Last)25
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LAB EXAM 1 EXERCISES31
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LAB EXAM 1 PPT CULTURE MEDIA107
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Module 13 (VIRUSES)64
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Module Virology Pt.1 (RNA VIRUSES)85
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Module Virology Part 2 (DNA)57
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Module VIROLOGY Part 3 (Introduction)98
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RNA (Picorna-Coronaviridae)83
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RNA VIRUS (REO - RHABDOVIRIDAE)49
