Anaerobic Respiration

Question 1

How does lack of oxygen affect respiration?

Answer 1

• Oxygen is the final proton and electron acceptor
• Without it the ETC stops
• So reduced NAD cannot be oxidised and release hydrogen
• Accumulation of reduced NAD causes no oxidised NAD being regenerated
• With no NAD, link reaction, Krebs cycle and glycolysis can’t happen

Question 2

What type of anaerobic respiration do animals undergo?

Answer 2

Lactate fermentation

Question 3

How does lactate fermentation solve the lack of oxygen problem for respiration?

Answer 3

Regenerates NAD so glycolysis can occur which needs no oxygen

Question 4

Explain lactate fermentation

Answer 4

• 1x glucose is phosphorylated then oxidised to form 2x 3C pyruvate
• ADP is substrate level phosphorylated to form ATP (Pi comes from glucose
• NAD gains electrons and H from glucose converstion to pyruvate and becomes reduced NAD
• Electrons and Hs of reduced NAD are transferred to pyruvate
• Reduces it to lactate
• Reduced NAD is therefore oxidised into NAD and can be used again in glycolysis

Question 5

What is the net gain of ATP in lactate fermentation?

Answer 5

2 per glucose

Question 6

What is the advantage of anaerobic respiration?

Answer 6

Rapid

Question 7

What is the disadvantage of anaerobic respiration?

Answer 7

Inefficient

Question 8

What is the problem that lactate causes in cells?

Answer 8

• Lactate dissolves in solution to form lactic acid

- Lactate accumulation causes cell pH to fall

Question 9

What is the problem for respiration in cell pH falling? 5

Answer 9

• Inhibits enzymes catalysing glycolysis reactions
• Amino acids making up enzymes have positive/negative groups
• Negatively charged groups in active site are neutralised by positive H+ ions in the blood
• Affects attraction between charged groups on substrate and enzyme active site
• Substrate can no longer bind to active site and glycolysis stops

Question 10

What is the effect of lactate fermentation? 2

Answer 10

• Muscle cramp

- Person slows down so oxygen supply can supply demand

Question 11

What happens after exercise?

Answer 11

Oxygen debt

Question 12

What is oxygen debt?

Answer 12

Excess oxygen requirement in recovery period after exercise where oxygen uptake is greater than normal

Question 13

Why is there an oxygen debt after exercise?

Answer 13

Needed to fuel oxidation of extra pyruvate the lactate is converted back into

Question 14

How is lactate removed? 3

Answer 14

• Occurs via Kreb’s cycle where excess pyruvate is oxidised directly into CO2 and H2O
• Releases energy for ATP synthesis
• Lactate converted into glycogen and stored in muscle/liver

Question 15

What is the ATP/PC system used for?

Answer 15

Provides burst of energy for 6-10 seconds at the beginning of rapid exercise

Question 16

Why is the ATP/PC system needed? 2

Answer 16

• Cells can only store a small amount of ATP - enough for a few seconds
• Regeneration must be rapid
• B/c at the start of exercise, rest of body not caught up with new oxygen demand through blood circulation

Question 17

What chemical is used in the ATP/PC system?

Answer 17

Creatine phosphate [PC]

Question 18

Where is PC stored?

Answer 18

In the muscles

Question 19

Explain how the ATP/PC system works

Answer 19

• Triggered by ATP formed at start of exercise
• PC is hydrolysed
• Releases energy and a phosphate group
• Energy used to regenerate ATP from ADP and Pi
• PC stores regenerated from ATP at rest

Question 20

What are the two equations in the ATP/PC system and therefore the overall equation?

Answer 20

• Creatine phosphate —] creatine + Pi
• ADP and Pi —] ATP

Overall: creatine phosphate + ADP —-] creatine + ATP

Question 21

Is oxygen needed for the ATP/PC system?

Answer 21

No