18.6 Respiratory substrates

Question 1

What other organic molecules can be broken down to release energy for the synthesis of ATP? (2 marks)

Answer 1

Triglycerides
Proteins

Question 2

Describe how triglycerides enter the respiratory cycle. (3 marks)

Answer 2

The triglycerides are hydrolysed to fatty acids, which enter the Krebs cycle via acetyl coenzyme A and glycerol.

Question 3

Describe how proteins enter the respiratory cycle. (3 marks)

Answer 3

Proteins are hydrolysed into amino acids, these are the deaminated and enter the respiratory pathway via pyruvate.

Question 4

How is the respiratory quotient calculated? (1 mark)

Answer 4

volume of carbon dioxide produced/ volume of oxygen consumed

Question 5

Give the rough respiratory quotients of lipids, proteins, and carbohydrates.

Answer 5

Lipids= 0.7
Proteins= 0.9
Carbohydrates= 1.0

Question 6

Put these organic molecules of least to most carbon-hydrogen bonds (2 marks):
Lipids
Proteins
Alcohols
Carbohydrates

Answer 6

Carbohydrates and proteins, alcohols, lipids

Question 7

What is the correlation between number of carbon-hydrogen bonds and energy released for the synthesis of ATP? (1 mark)

Answer 7

The more carbon-hydrogen bonds there are, the more energy released when broken down.

Question 8

What value of a respiratory quotient indicates anaerobic respiration?

Answer 8

Above 1.0

Question 9

How are respiratory quotients measured? (1 mark)

Answer 9

Using a respirometer

Question 10

What does a respirometer contain that absorbs carbon dioxide? (1 mark)

Answer 10

Potassium hydroxide (KOH) solution

Question 11

Describe how a respirometer works. (4 marks)

Answer 11

The specimen is placed on a piece of mesh in the respirometer, a stopper is put in the tube, and a graduated tube is in the top of it, containing some coloured liquid.
As the specimen respires, the volume of air in the tube changes, this is shown by the liquid moving up/down the graduated tube.