18.5 Anaerobic respiration

Question 1

Does anaerobic respiration produce more or less ATP than aerobic respiration? (1 mark)

Answer 1

Less

Question 2

What are the three categories of organisms determined by their dependence on oxygen? (3 marks)

Answer 2

Obligate anaerobes
Facultative anaerobes
Obligate aerobes

Question 3

What is an obligate anaerobe? (1 mark)

Answer 3

Organisms that cannot survive in the presence of oxygen

Question 4

What is a facultative anaerobe? (1 mark)

Answer 4

Organisms that synthesise ATP by aerobic respiration when oxygen is avalaible, but switch to anaerobic respiration in the absence of oxygen.

Question 5

What is an obligate aerobe? (1 mark)

Answer 5

Organisms that can only survive in the presence of oxygen.

Question 6

Define fermentation. (3 marks)

Answer 6

A form of anaerobic respiration; complex organic compounds are broken down into simpler inorganic compounds, without using oxygen or an electron transport chain.

Question 7

How is ATP produced in fermentation? (1 mark)

Answer 7

Substrate level phosphorylation

Question 8

What organisms does lactate fermentation happen in? (1 mark)

Answer 8

Mammals

Question 9

Why are mammals classed as obligate aerobes even though they use both aerobic and anaerobic respiration? (3 marks)

Answer 9

Mammals can only respire anaerobically for a short period of time, because lactic acid builds up which lowers the pH of the blood. This more acidic environment causes respiratory enzymes to denature.

Question 10

How does lactate fermentation work? (2 marks)

Answer 10

Pyruvate accepts a hydrogen from NADH to form lactic acid and NAD. The NAD produced keeps glycolysis going.

Question 11

What enzyme catalyses lactate fermentation? (1 mark)

Answer 11

Lactate dehydrogenase

Question 12

How does the body get rid of lactic acid? (1 mark)

Answer 12

Lactic acid is converted back to glucose in liver, oxygen is needed for this process.

Question 13

Why can lactate fermentation continue indefinitely? (2 marks)

Answer 13

1. It does not produce enough ATP to maintain vital processes for a long period of time.
2. The accumulation of lactic acid causes the blood pH to lower, causing proteins to denature.

Question 14

Is alcoholic fermentation reversible? (1 mark)

Answer 14

No.

Question 15

In what organisms does alcoholic fermentation take place? (1 mark)

Answer 15

Yeast and many plants

Question 16

How does alcoholic fermentation work? (3 marks)

Answer 16

Pyruvate is decarboxylated to produce ethanal, the ethanal then accepts a hydrogen from NADH to form ethanol and NAD. The NAD produced keeps glycolysis going.

Question 17

Can alcoholic fermentation continue indefinitely? (1 mark)

Answer 17

Yes.

Question 18

What is one problem with alcoholic fermentation for yeast cells? (2 marks)

Answer 18

Ethanol is a toxic waste product for yeast, they are unable to survive if over 15% of ethanol accumulates.

Question 19

How are bacteria adapted to survive in low oxygen conditions? (1 mark)

Answer 19

They can use nitrate/sulfate/carbon dioxide as a final electron acceptor.

Question 20

How are marine mammals adapted to survive underwater? (4 marks)

Answer 20

• Have a greater concentration of haemoglobin and myoglobin.
  -Have a higher tolerance to lactic acid and carbon dioxide, due to really good blood buffering systems.
  -Peripheral vasoconstriction when dive (blood goes to heart, muscles, and brain).
  -Exchange 80-95% of air in lungs.
  -Streamline qualities- reduces friction with water and therefore the energy needed from respiration.