Respiration

Question 1

Earthworms cannot survive for very long in heavily waterlogged soil.
Suggest why this is the case.
[1]

Answer 1

They cannot respire anaerobically (for very long); [1 mark]
Lactic acid lowers the pH of their cells/makes the cells acidic / causes enzymes in their cells to denature; [1 mark]
Anaerobic respiration releases less energy / does not release enough energy; [1 mark]
[Total: 1 mark]

Question 2

An oxygen debt is often associated with anaerobic respiration.
Describe the process that occurs in the human body during an oxygen debt.
[2]

Answer 2

Deeper/faster/harder breathing to supply oxygen; [1 mark]
Oxygen is used to break down lactic acid; [1 mark]
Lactic acid is converted to glucose; [1 mark]
Carbon dioxide / water released as a waste product; [1 mark]

Question 3

In the absence of sufficient oxygen, cells respire anaerobically.
Compare anaerobic respiration in the muscle cell of an animal with anaerobic respiration in a yeast cell.
[3]

Answer 3

Both release/transfer (relatively) small amounts of energy; [1 mark]
Lactic acid is produced in animal muscle cells WHILE ethanol is produced in yeast cells; [1 mark]
Carbon dioxide is produced in yeast WHILE it is not in animal muscle cells; [1 mark]
Award marking points 2 and 3 for word equations for anaerobic respiration in animal and yeast cells, e.g.

Animals: Glucose → lactic acid; [1 mark]
Yeast: Glucose → ethanol + carbon dioxide; [1 mark]

Question 4

In order to collect the data about carbon dioxide produced by the roots of the plant, scientists took samples of the air from the soil around the plant roots and adjusted it to account for atmospheric carbon dioxide levels.
Suggest why the readings they took may still be higher than the actual rate of carbon dioxide production in the plant roots. [1]

Answer 4

Respiration of other organisms/microorganisms/decomposers in the soil (produces carbon dioxide); [1 mark]
I said, Co2 is trapped and there is less O2 than in the air

Question 5

Give a definition of the term ‘respiration’. [3]

Answer 5

Respiration is…

A chemical process / reaction in cells; [1 mark]
That is exothermic / supplies / releases / generates energy; [1 mark]
Plus one of the following:

Releases carbon dioxide / CO2 / water / H2O / lactic acid / ethanol; [1 mark]
From glucose/food substances (and oxygen); [1 mark]
Ignore references to breathing
Ignore ‘produces / makes energy’