5.1 - 5.4 Aerobic respiration

Question 1

Explain why cells respond to hypoxia with an increase in the rate of glycolysis

Answer 1

• (because if conditions are hypoxic) there is not much oxygen available to act as a terminal electron acceptor (1)
• therefore the electron transport chain will not operate (1)
• therefore ATP production by oxidative phosphorylation will be reduced (1)
• ATP is produced (directly ) during glycolysis (during these
  anaerobic conditions) (1)

Question 2

state the purpose of aerobic respiration

Answer 2

produces ATP, which can be hydrolysed to ADP+Pi
To release energy for metabolic reaction/phosphorylate compounds to make them more reactive

Question 3

Name the 4 main stages in aerobic respiration and where they occur

Answer 3

glycoloysis - cytoplasm
link reaction - mitochondrial matrix
krebs cycle - mitochondrial matrix
oxidative phosphorylation - across inner mitochondrial membrane

Question 4

outline the stages of glycolysis

Answer 4

1. glucose is phosphorylatedfru to fructose biphosphate by 2 ATP–> 2ADP (to prevent it from leaving the cell and make it more reactive)
2. fructose biphosphate splits into 2 x glyceraldehyde phosphate
3. The 2 glyceraldehydes are oxidised to two pyruvate by NAD+–> NADH and 2ADP—> 2ATP

NET : 2ATP and 2NADH

Question 5

How does pyruvate from glycolysis enter the mitochondria

Answer 5

active transport

Question 6

what happens in the link reaction

Answer 6

1. complete oxidation of pyruvate to acetate
   ( per pyruvate molecule : net gain 1xCO2 molcule (decarboxylation) and 2H atoms (used to reduce 1xNAD))
2. Acetate combines with coenzyme A (CoA) to form acetylcoenzyme A

Question 7

give a summary equation for the link reaction

Answer 7

pyruvate + NAD + CoA –> acetyl CoA + reduced NAD + CO2

Question 8

what happens in the Krebs cycle?

Answer 8

series of redox reactions produces
- atp by substrate level phosphorylation
- reduced coenzymes eg NADH
- CO2 from decarboylation

Question 9

substrate level vs oxidative phosphorylation

Answer 9

substrate level is when ADP is phosphorylated by a substrate to produce ATP. Oxidative is the phosphorylation of ADP to ATP using the free energy produced from redox reactions in the electron transport chain.

Question 10

what is the electron transport chain?

Answer 10

a series of carrier proteins embedded in membrane of the cristae of mitochondria

Question 11

name the process that the electron transfer chain uses to produce ATP in aerobic respiration

Answer 11

oxidative phosphorylation via chemiosmosis

Question 12

what is NADH/FADH

Answer 12

reduced coenzyme

Question 13

what happens in the elctron ransfer chain

Answer 13

electrons released from reduced NAD and FAD undergo successive redox reactions
the energy released is couples to maintaing proton gradient or released as heat
oxygen acts as final electron acceptor

Question 14

how is a proton concentration gradient established during chemiosmosis in aerobic respiration?

Answer 14

some energy released from the ETC is coupled to the active transport of H+ ions (protons) from the mitochondrial matrix into the intermembrane space

Question 15

how does chemiosmosis produce ATP during aerobic respiration?

Answer 15

H+ ions (protons) move down their conc gradient from the intermembrane space into the mitochondrail matrix via the channel protein ATP synthase. ATP synthase catalyses ADP+Pi–> ATP

Question 16

State the role of oxygen in aerobic respiration

Answer 16

final electron acceptor in electron transfer chain (produces water as a byproduct)

Question 17

what is the benefit of an electron transfer chain rather than a single reaction?

Answer 17

• energy is released gradually
• less energy is released as heat