Respiration

Question 1

Explain why all life needs to perform respiration.

Answer 1

Needs energy to perform metabolic processes such as; transport, synthesis, movement

Question 2

Explain why ATP is a better, immediate source of energy for metabolic reactions than glucose.

Answer 2

1. Inter-conversion of ATP and ADP is happening constantly in all living cells, meaning cells do not need a large store of ATP.
2. Small- moves easily into and out of cells
3. Water soluble- energy requiring processes happen in aqueous environments
4. Contain bonds between phosphates with intermediate energy; large enough to be useful for cellular reactions but not so large that energy would be wasted as heat.
5. Releases energy in small quantities- suitable to most cellular needs so that energy is not wasted as heat.
6. Easily regenerated

Question 3

Draw, label and annotate a diagram of a mitochondrion.

Answer 3

1. Outer mitochondrial membrane- separates the contents of the mitochondrion from the rest of the cell, creating a cellular compartment with ideal conditions.
2. Inner mitochondrial membrane- contains electron transport chains and ATP synthase
3. Cristae- are projections of the inner membrane which increase the surface area available for oxidative phosphorylation.
4. Matrix- contains enzymes for the Krebs Cycle and the link reaction, also contains mitochondrial DNA.
5. Inter-membrane space- Protons are pumped into this space by the electron chain. The space is small so the concentration builds up quickly.

Question 4

State the site of glycolysis within cells.

Answer 4

In the cytoplasm of the cell.

Question 5

Describe the steps of the process of glycolysis.

Answer 5

1. Phosphorylation- the first step of glycolysis requires two molecules of ATP. Two phosphates released from the two ATP molecules, are attached to a glucose molecules forming hexose bisphosphate
2. Lysis- this destabilises the molecule causing it to split into two triose phosphate molecules.
3. Phosphorylation- another phosphate group is added to each triose phosphate forming two triose bi-phosphate molecules. These phosphate groups come from free inorganic phosphate ions present in the cytoplasm.
4. Dehydrogenation and formation of ATP- the two triose bisphosphate molecules are then oxidised by the removal of hydrogen atoms to form two pyruvate molecules. NAD co-enzymes accept the removed hydrogens-they are reduced, forming two reduced NAD molecules.
5. At the same time 4 ATP molecules are produced.

Question 6

Give an example of substrate level phosphorylation and describe what it is.

Answer 6

1. Synthesis of ATP by transfer of phosphate molecule from another molecule. (a phosphorylated intermediate (e.g triose bisphosphate))
2. The formation of ATP without the involvement of an electron transport chain.
3. An example is glycolysis

Question 7

State the molecules/conditions required for glycolysis

Answer 7

1. Glucose
2. 2 molecules of ATP
3. Co-enzyme NAD
4. Phosphate ions
5. No oxygen required

Question 8

State the products from glycolysis

Answer 8

1. 4 molecules of ATP (net of 2)- used for energy
2. 2 reduced NAD- used in later stage to synthesise more ATP
3. 2 Molecules of pyruvate- Used in Link reaction of respiration

Question 9

Define dehydrogenation

Answer 9

The removal of a hydrogen atom

Question 10

State the site of the link reaction within cells.

Answer 10

Mitochondrial matrix

Question 11

Describe the process of the link reaction.

Answer 11

1. Oxidative Decarboxylation
2. Step that links anaerobic glycolysis in the cytoplasm to aerobic steps if respiration in the rest of the mitochondria
3. Pyruvate enters the mitochondrial matrix by active transport via specific carrier proteins.
4. Pyruvate then undergoes oxidative decarboxylation- CO2 is removed (decarboxylation) along with hydrogen( oxidation).
5. The hydrogen atoms removed are accepted by NAD to form reduced NAD.
6. The resulting two-carbon acetyl group is bound by co-enzyme A forming acetylcoenzyme (acetyl CoA).
7. Acetyl CoA delivers the acetyl groups to the next stage of aerobic respiration- Krebs cycle
8. Reduced NAD is used in oxidative phosphorylation to synthesis ATP
9. Acetyl groups are now all that is left of the original glucose molecules- CO2 will diffuse away and be removed as metabolic waste or may be used as raw material in photosynthesis.

Question 12

State the molecules required for the link reaction

Answer 12

1. CO enzyme A
2. pyruvate
3. NAD

Question 13

State the products for the link reactions

Answer 13

1. CO2- diffuse or used in photosynthesis
2. Reduced NAD- oxidative phosphorylation
3. Acetyl CoA- delivers acetyl groups to Krebs cycle

Question 14

Define the term decarboxylation

Answer 14

Removal of carbon dioxide

Question 15

Define the term oxidative decarboxylation

Answer 15

Removal of carbon dioxide along with hydrogen

Question 16

State the site of the Krebs cycle within cells.

Answer 16

Mitochondrial matrix

Question 17

Draw a diagram to show the process of the Krebs cycle.

Answer 17

Two Cycles happen at the same time

1. Acetyl CoA delvers an acetyl groups (whats left of the glucose from pyruvate) to the Krebs cycles
2. The two-carbon acetyl group combines with four-carbon oxaloacetate to form six-carbon citrate
3. The citrate molecule undergoes decarboxylation and dehydrogenation producing one reduced NAD and carbon dioxide. A five-carbon compound is formed.
4. The five-carbon compound undergoes further decarboxylation and dehydrogenation reactions eventually regenerating oxaloacetate and so the cycle continues.
5. While oxaloacetate is regenerated, ATP is produced by substrate level phosphorylation- direct transfer of a phosphate group from an intermediate compound to ADP.
6. Also produced is more CO2, two more reduced NADs and one reduced FAD are produced.

Question 18

State the molecules required for the Krebs cycle

Answer 18

1. NAD
2. FAD
3. ADP + P
4. Acetyl CoA to deliver acetyl group
5. Oxaloacetate

Question 19

State the products of the Krebs cycle

Answer 19

From two simultaneous cycles (divide by 2 for products of one)

1. ATP x2 - Energy
2. Reduced FAD x2 (FADH2) -coenzyme that delivers electrons to transport chain
3. Reduced NAD x6 -coenzyme that delivers electrons to transport chain
4. CO2 x4- by product
5. Oxaloacetate x2- Re-used in Krebs cycle to combine with acetyl group

Question 20

Draw a table to summarise the products of glycolysis, the link reaction and the Krebs cycle for one molecules of glucose.

Answer 20

1. 10 x reduced NAD
2. 2 x FADH2
3. 4 x ATP
4. 6 x CO2

Question 21

Name 3 coenzymes involved in respiration and describe the function of each.

Answer 21

1. NAD- delivers electrons to electron transport chain
2. FAD- delivers electrons to electron transport chain
3. Acetyl CoA- delivers acetyl group to Krebs cycle

Question 22

Describe the similarities and differences between FAD and NAD.

Answer 22

1. NAD takes part in all stages of cellular respiration but FAD only accepts hydrogen in the Krebs cycle
2. NAD accepts one hydrogen and FAD accepts two.
3. Reduced NAD is oxidised at the start of the electron transport chain releasing protons and electrons while reduced FAD is oxidised further along the chain.
4. Reduced NAD results in the synthesis of three ATP molecules but reduced FAD results in the synthesis of only two ATP molecules.

Question 23

Define the term oxidative phosphorylation

Answer 23

The process where energy carried by electrons from coenzymes (NAD and FAD) is used to make ATP

Question 24

Define electron carrier

Answer 24

Proteins that accept and release electrons

Question 25

Define electron transport chain

Answer 25

1. It is made up of a series of electron carriers each with progressively lower energy levels. 2. As high energy electrons move from one carrier in the chain to another, energy is released.

Question 26

Define the term chemiosmosis

Answer 26

The synthesis of ATP driven by the flow of protons across a membrane

Question 27

State the site of oxidative phosphorylation within cells.

Answer 27

The folded membrane (cristae) of mitochondria.

Question 28

Describe the process of oxidative phosphorylation.

Answer 28

1. The hydrogen atoms that have been collected by coenzymes NAD and FAD are delivered to electron transport chains present in the membranes of the cristae of the mitochondria. 2. The hydrogen atoms dissociate into hydrogen ions and electrons. 3. The high energy electrons are used in the synthesis of ATP by chemiosmosis. 4. Energy is released during redox reactions as the electrons reduce and oxidise electron carriers as they flow along the electron transport chain. 5. The energy is used to create a proton gradient leading to the diffusion of protons through ATP synthase resulting in the synthesis of ATP. 6. At the end of the chain the electrons combine with hydrogen ions and oxygen to form water. 7. Oxygen is the final electron acceptor and the electron chain cannot operate unless oxygen is present.

Question 29

Describe the role of mitochondrial cristae in the process of oxidative phosphorylation.

Answer 29

1. Contains electrons transport chain for generating ATP | 2. Projections- cristae- increase surface area available for oxidative phosphorylation

Question 30

State the molecules required for oxidative phosphorylation

Answer 30

1. Oxygen | 2. Reduced NAD and FAD

Question 31

State the products from oxidative phosphorylation and the fate of the products from oxidative phosphorylation.

Answer 31

1. ATP- energy source | 2. Water- by-product.

Question 32

Name two sites of chemiosmosis in cells.

Answer 32

1. Cristae | 2. grana- thylakoid membrane

Question 33

Summarise how ATP can be produced by chemiosmosis.

Answer 33

1. High energy electrons move form one carrier to another and this releases energy. 2. This energy is used to pump protons across a membrane, creating a concentration difference across the membrane and therefore a proton gradient. 3. The proton gradient is maintained as a result of the impermeability of the membrane to hydrogen ions. 4. The only way the protons can move back through the membrane down their concentration gradient is through hydrophillic membrane channels linked to the enzyme ATP synthase (catalyses the formation of ATP). 5. The flow of protons through theses channels provides the energy used to synthesise ATP.

Question 34

Draw a table to compare chemiosmosis in photosynthesis with chemiosmosis in respiration.

Answer 34

1. Oxidative phosphorylation in respiration 2. Photophosphorylation in photosynthesis. 3. In photosynthesis ATP is used to synthesise glucose and other organic mocecules 4. In respiration ATP produced provides the energy needed by metabolic processes and reactions essential to life.

Question 35

Define the term anaerobic respiration

Answer 35

Respiration in the absence of oxygen

Question 36

Define obligate anaerobe

Answer 36

Organisms that cannot live in environments containing oxygen

Question 37

Define obligate aerobe

Answer 37

Organisms that can only respire aerobically

Question 38

Define facultative anaerobes

Answer 38

Organisms that can respire anaerobically or aerobically

Question 39

Fermentation

Answer 39

Anaerobic respiration without the involvement of an electron transport chain.

Question 40

Alcoholic fermentation

Answer 40

Fermentation that results in the production of ethanol

Question 41

Lactate fermentation

Answer 41

Fermentation that results in the production of lactate.

Question 42

Name the types of organisms that are obligate anaerobes, facultative anaerobes and obligate aerobes

Answer 42

1. Obligate anaerobe- almost all are prokaryotes although there are some fungi as well. 2. Facultative anaerobes- yeast 3 Obligate aerobes- mammals, the individual cells of some organisms can be described as facultative anaerobes (e.g. muscle cells in mammals.

Question 43

Name the types of cell that do alcoholic fermentation and the types of cell that do lactate fermentation.

Answer 43

Alcoholic fermentation- yeast and some plant root cells | Lactate fermentation- animal cells

Question 44

Describe the usefulness of anaerobic respiration.

Answer 44

It is a temporary emergency measure to keep vital processes running when oxygen cannot be supplied fast enough to respiring cells.

Question 45

Describe the process of alcoholic fermentation

Answer 45

1. Alcoholic fermentation is not a reversible process like lactate fermentation. 2. Pyruvate is first converted to ethanal, catalysed by the enzyme pyruvate decarboxylase. 3. Ethanal can then accept a hydrogen atom from reduced NAD, becoming ethanol. 4. The regenerated NAD can then continue to act as a coenzyme and glycolysis can continue 5. This is not a short-term process can can continue indefinitely in the absence of oxygen 6. Ethanol is a toxic waste product to yeast cells and they are unable to survive if ethanol accumulates above approximately 15%

Question 46

Describe the process of lactate fermentation

Answer 46

1. Pyruvate can act as a hydrogen acceptor taking the hydrogen from the reduced NAD, catalysed by the enzyme lactate dehydrogenase. The pyruvate is converted to lactate (lactic acid) and NAD regenerated. 2. This can be used to keep glycolysis going so a small quantity of ATP is still synthesised. 3. In mammals in particular, anaerobic respiration in the muscles is often supported by ATP from aerobic respiration, which is still being produced as fast as oxygen can be delivered in other parts of the body. 4. Lactic acid is converted back to glucose in the liver but oxygen is needed to complete this process. This is the reason for the oxygen debt and the need to breathe heavily after exercise.

Question 47

Why can lactate fermentation not occur indefinitely .

Answer 47

1. It cannot occur indefinitely because the reduced quantity of ATP produced would not be enough to maintain vital processes for a long period of time. 2. The accumulation of lactic acid causes a fall in pH leading to proteins denaturing. Respiratory enzymes and muscle filaments are made from proteins and will cease to function at low pH.

Question 48

Explain why the yield of ATP from anaerobic respiration is much lower than the yield from aerobic respiration.

Answer 48

1. Because there is no oxygen to act as the final electron acceptor at the end of the electron transport chain in oxidative phosphorylation, the flow of electrons stop. This means the synthesis of ATP by chemiosmosis also stops. 2. As the flow of electrons along the electron transport chain has stopped, the reduced NAD and reduced FAD are no longer able to be oxidised because there is nowhere for the electrons to go. 3. This means NAD and FAD cannot be regenerated and so the decarboxylation and oxidation of pyruvate and the Krebs cycle comes to a halt as there are no coenzymes available to accept the hydrogen atoms being removed. 4. Glycolysis would come to a halt due to the lack of NAD if it were not for the process of fermentation. 5. There is no transport chain which is what generates the majority of ATP in aerobic respiration.

Question 49

Explain why glycolysis is the process that continues in anaerobic respiration whereas the link reaction, the Krebs cycle and oxidative phosphorylation all stop.

Answer 49

1. Because NAD is produced, so a small amount of glycolysis can take place. 2. But there is not enough to be used in Krebs and Link so they have nothing to accept hydrogen atoms 3. No oxygen for oxidative phosphorylation

Question 50

Explain why the regeneration of NAD is the crucial part of either form of fermentation.

Answer 50

Because that is the thing that is needed for glycolysis

Question 51

Describe how the rate of anaerobic respiration and aerobic respiration can be measured in yeast.

Answer 51

1. Measure volume of CO2 released 2. Have glucose in a sealed flask to ensure anaerobic conditions. 3. As the yeast respires Carbon dioxide is released increasing the volume of gas in the flask. Measure the volume of gas produced using a gas syringe. 4. Calculate the volume of CO2 produced in a given time. 5. You can use a data logger as well with a CO2 sensor as this can also measure changes in temperature which can be used to measure heat energy lost. 6. Insert the CO2 sensor into a flask containing glucose and yeast and cover the solution with a layer of paraffin.

Question 52

Define the term respiratory substrate

Answer 52

Organic molecules broken down in respiration

Question 53

Define relative energy value

Answer 53

The energy liberated in aerobic respiration?

Question 54

Describe how triglycerides are used in respiration

Answer 54

1. Triglycerides are hydrolysed to glycerol and fatty acids. 2. Glycerol is first converted to pyruvate before undergoing oxidative decarboxylation producing an acetyl group which is picked up by coenzyme A forming Acetyl CoA. 3. The fatty acids in a triglyceride molecule can be converted to acetyl groups which combine with coenzyme A to form acetyl CoA by beta oxidation without being converted to pyruvate first. This can lead to the formation of as many as 50 acetyl CoA molecules resulting in the synthesis of up to 500 ATP 4. Produce more energy than alcohol and carbs

Question 55

Describe how proteins are used in respiration.

Answer 55

1. Proteins first have to be hydrolysed to amino acids 2. Then the amino acids have to be deaminated (removal amine groups) before they enter the respiratory pathway usually via pyruvate. 3. These steps require ATP reducing the net production of ATP 4. Proteins produce roughly the same amount of energy as carbs

Question 56

Define the term “respiratory quotient (RQ)” and write the equation for the respiratory quotient.

Answer 56

1. Ratio of carbon dioxide produce to oxygen used in respiration. 2. RQ= CO2 produced / O2 consumed 3. It is measured using a respirometer,

Question 57

State the typical respiratory quotients for carbohydrates, proteins and lipids.

Answer 57

1. Carbohydrates= 1.0 2. Proteins = 0.9 3. Lipids= 0.7

Question 58

Describe the differences in the respiratory quotients

Answer 58

1. Lipids contain a greater proportion of carbon-hydrogen bonds than carbohydrates which is why they produce so much more ATP in respiration. 2. Due to the greater number of carbon-hydrogen bonds, lipids require relatively more oxygen to break them down and release relatively less carbon dioxide. 3. This results in RQs of less than 1 for lipids 4. The structure of amino acids leads to RQs somewhere between carbohydrates and lipids 5. It takes 6 oxygen molecules to completely respire 1 molecule of glucose and this results in the production of 6 molecules of carbon dioxide, resulting in an RQ value of 1.0

Question 59

Describe how a respirometer can be used to provide information about which respiratory substrate might be being used by an organism at a particular point, and explain why there may be alternative explanations for an organisms RQ value.

Answer 59

1. During normal activity the RQ is in the range of 0.8 to 0.9 showing that carbohydrates and lipids (and probably some proteins) are being use as respiratory substrates. 2. During aerobic respiration, the RQ increases above 1.0 although this is not easy to measure as the point at which anaerobic respiration begins is not easy to pinpoint. 3. You can use respirometer to measure the RQ which can tel you what is being used.

Question 60

Describe a step by step method to investigate the effect of one factor (temperature, substrate concentration, or different respiratory substrate) on the rate of respiration.

Answer 60

1. Use a respirometer 2. The potassium hydroxide in the apparatus absorbs CO2 so if the temperature is kept the same, any changes in the volume of air in the respirometer will be due to oxygen uptake. 3. You can set up different respirometers with different conditions 4. Measure the distance the coloured fluid moves in the graduated tube after being left for 20 mins.