Respiration A2

Question 1

The mitochondria in muscles contain
many cristae. Explain the advantage of
this. (2)

Answer 1

● larger surface area for electron carrier system /
oxidative phosphorylation;
● provide ATP / energy for contraction;

Question 2

Describe how oxidation takes place in
glycolysis and in the Krebs cycle. (4)

Answer 2

● removal of hydrogen /dehydrogenation;
● by enzymes /dehydrogenases;
● H accepted by NAD/reduced NAD formed;
● in Krebs cycle, FAD (used as well);

Question 3

Water is a waste product of aerobic respiration. Describe how water is formed at the end of aerobic
respiration. (2)

Answer 3

● oxygen is terminal/final electron acceptor;
● combines with electron and hydrogen (to form
water);

Question 4

Explain how the amount of ATP is
increased by reactions occurring inside
a mitochondrion. (12)

Answer 4

● oxidation of/removal of electrons / removal of H+
● from pyruvate/
● acetyl CoA / 6 carbon compound; (credit oxidative decarboxylation)
● substrate level production of ATP / ATP produced in Krebs cycle;
● production of reduced NAD / FAD (allow they take up hydrogen);
● in matrix of mitochondria;
● electrons fed into electron transport chain / used in oxidative
● (Electrons) pass along carriers/through electron transport chain/through series of redox reactions;
● Energy released;
● Protons move into intermembrane space;
● ADP/ADP + Pi;
● ATP synthase;

Question 5

Describe the roles of the coenzymes
and carrier proteins in the synthesis of
ATP. (7)

Answer 5

● NAD/FAD reduced / hydrogen attached to NAD/FAD;
● H+ ions/electrons transferred from coenzyme to coenzyme/carrier to carrier
● series of redox reactions;
● energy made available as electrons passed on;
● energy used to synthesise ATP from ADP and phosphate / using ATPase;
● H+/ protons passed into intermembrane space;
● H+/ protons flow back through stalked particles/enzyme;

Question 6

Describe the events of oxidative
phosphorylation. (7)

Answer 6

● NAD/FAD reduced / hydrogen attached to
NAD/FAD;
● ETC on cristae / inner membrane;
● H+ ions/electrons transferred from coenzyme to coenzyme/carrier to carrier / series of redox reactions;
● energy made available as electrons passed on;
● H+ / protons passed into intermembrane space;
● H+ / protons flow back through stalked
particles/enzyme;
● energy used to synthesise ATP from ADP and phosphate / using ATP synthase;

Question 7

Which part of the mitochondria does the Kreb’s cycle take place in?

Answer 7

matrix

Question 8

Name two substances for which there would be net movement into the mitochondrion.

Answer 8

1. pyruvate
2. ADP or reduced NAD (NADH)

Question 9

The mitochondria in muscles contain many cristae. Explain the advantage of this.

Answer 9

1. larger surface area for electron carrier system
2. provides ATP/energy for contraction

Question 10

Water is a waste product of aerobic respiration. Describe how water is formed at the end of aerobic respiration.

Answer 10

1. oxygen is terminal / final electron acceptor
2. combines with electron and hydrogen (to form water)

Question 11

Where in cell does glycolysis occur?

Answer 11

cytoplasm of cell

Question 12

Describe and explain how inhibition of glycolysis will affect the production of ATP by the electron transfer chain.

Answer 12

1. ATP production inhibited
2. no reduced NAD released
3. no pyruvate/link reaction/Krebs cycle inhibited
4. Movement of electrons/protons/hydrogens down chain stops (no electrochemical gradient)
5. no release of free energy to phosphorylated ADP

Question 13

Name the 3 carbon end product of glycolysis.

Answer 13

pyruvate

Question 14

Describe how pyruvate is converted into a substance that enters the Krebs cycle.

Answer 14

1. reacts with (coenzyme A) to give acetyl co-enzyme A
2. decarboxylation / CO2 given off
3. NAD reduced / oxidation

Question 15

Explain why radioactivity only began to appear in the gas produced by cells after oxygen was introduced.

Answer 15

1. only glycolysis in anaerobic conditions
2. with oxygen, get aerobic respiration so link reaction occurs + Krebs cycle
3. therefore release of radioactively added CO2
4. as CO2 is given off in link reaction

Question 16

Explain why oxygen is needed for the production of ATP on the cristae of the mitochondria.

Answer 16

1. ATP formed as electrons pass along transport chain
2. oxygen is terminal electron acceptor / accepts electrons from electron transport chain
3. electrons cannot be passed along electron transport chain if no O2 to accept them
4. forms H2O / accepts H+ from reduced NAD/FAD (NADH/FADH)

Question 17

Explain how the amount of ATP is increased by reactions occurring inside a mitochondrion.

Answer 17

1. oxidation of electrons / removal of H+ from pyruvate
2. ATP produced in Krebs cycle
3. production of reduced NAD/FAD (take up the hydrogen)
4. in matrix of mitochondria
5. electrons fed into electron transport chain
6. on cristae
7. linked to ATP production
8. ATP synthase
9. electrons lose energy as passed along chain

Question 18

Give two properties of an ATP molecule that make it suitable as an immediate source of energy in cells.

Answer 18

1. can re rapidly re-synthesised
2. released in small amounts
3. easily hydrolysed

Question 19

Name two transport proteins found in the membrane surrounding a mitochondria and describe their function.

Answer 19

1. H+ ions/electrons transferred from carrier/coenzyme to coenzyme
2. ATP synthase - generates energy used to synthesise ATP from ADP + Pi

Question 20

People who suffer from chronic fatigue syndrome have some mitochondria in which some of these transport proteins are damaged. Explain how this might result in fatigue.

Answer 20

ATP cannot be synthesised / cannot leave mitochondria

Question 21

Explain the advantage of mitochondria in muscle cells having more cristae than in skin cells.

Answer 21

1. more cristae for electron transport chain / more enzyme for ATP production
2. muscle cells use more ATP

Question 22

In the link reaction, pyruvate is converted to a substance with molecules effectively containing only two carbon atoms. Describe what happens in this process.

Answer 22

1. CO2 formed
2. reduced NADP formed

Question 23

Describe the roles of coenzymes and carrier proteins in the synthesis of ATP.

Answer 23

1. H+ ions transferred from coenzyme to coenzyme in a series of redox reactions
2. energy used to synthesise ATP from ADP + Pi
3. H+ proton passed into intermembrane space
4. H+ protons flow back through stalked particles/enzymes

Question 24

Explain why scientists did not use glucose as the respiratory substrate, whilst adding various substances to the mitochondria and measuring the concentration of oxygen?

Answer 24

1. glucose breakdown / glycolysis occurs in the cytoplasm
2. glucose does not enter mitochondria / coenzyme not present
3. Krebs cycle occurs in matrix of mitochondria
4. glucose cannot be used in Krebs cycle

Question 25

The concentration of oxygen changes when ADP is added, explain why.

Answer 25

1. ADP used in electron transport chain 2. oxygen is final hydrogen acceptor used to form water

Question 26

The production of lactate allows glycolysis to continue in the absence of oxygen. Explain how.

Answer 26

1. regenerated NAD, oxidises reduced NAD 2. NAD needed for glycolysis

Question 27

Respiration produces less ATP from a molecule of glucose in the absence of oxygen than it does when oxygen is present. Explain why.

Answer 27

1. some energy still in lactate / incomplete breakdown of glucose 2. no Krebs cycle 3. no electron transport chain 4. as oxygen is terminal electron acceptor

Question 28

Give two reasons why the respirometer was left for 10 minutes when it was first placed in the water bath.

Answer 28

1. equilibrium reached 2. allows for expansion/pressure change 3. allows respiration rate of substance to stabilise

Question 29

During the investigation, the coloured liquid in the manometer moved towards tube A. Explain what caused this.

Answer 29

1. oxygen consumed by locust 2. CO2 given out and absorbed by KOH (potassium hydroxide) 3. reduction in volume/pressure

Question 30

What calculation would you use to measure rate of oxygen consumption by the locust?

Answer 30

(volume changed / mass) x correction for 1 hour

Question 31

Where in the cell is rubisco found?

Answer 31

stroma (of chloroplast)

Question 32

Name the four main stages in aerobic respiration and where they occur.

Answer 32

Glycolysis - cytoplasm Link reaction - mitochondrial matrix Krebs cycle - mitochondrial matrix Oxidative phosphorylation - via electron transfer chain - membrane of cristae

Question 33

Outline the stages of glycolysis.

Answer 33

1. Glucose is phosphorylated to glucose phosphate (GP) by 2x ATP 2. GP splits into 2 x TP 3. 2x TP is oxidised into 2x pyruvate 4. net gain of 2x reduced NAD and 2x ATP per glucose

Question 34

How does pyruvate from glycolysis enter the mitochondria?

Answer 34

Via active transport

Question 35

What happens during the link reaction?

Answer 35

1. Oxidation of pyruvate to acetate 2. per pyruvate molecule, net gain of 1x CO2 (decarboxylation) and 2H atoms (used to reduce 1x NAD 3. acetate combines with coenzyme A (CoA) to form acetyl-coenzyme A

Question 36

Give the summary equation for a link reaction.

Answer 36

Pyruvate + NAD + CoA = acetyl CoA + reduced NAD + CO2

Question 37

What happens in the Krebs cycle?

Answer 37

A series of redox reactions produce: 1. ATP by substrate level phosphorylation 2. reduced coenzymes 3. CO2 from decarboxylation

Question 38

What happens in the electron transfer chain?

Answer 38

1. electrons released from reduces NAD and FAD undergo successive redox reactions 2. the energy released is couples to maintaining proton gradient or released a heat 3. oxygen acts as final electron acceptor

Question 39

How can lipids act as an alternative respiratory substrate?

Answer 39

lipid -> glycerol + fatty acids 1. phosphorylation of glycerol to TP for glycolysis 2. fatty acid converts to acetate 3. acetate enters link reaction 4. H atoms produced for oxidative phosphorylation

Question 40

How can amino acids act as an alternative respiratory substrate?

Answer 40

Deamination produces: 1. 3 carbon compounds -> pyruvate for link reaction 2. 4C/5C compounds -> intermediates in Krebs cycle