Respiratory Substances

Question 1

What are respiratory substances?

Answer 1

Molecules that can be used as an energy source to allow the production of ATP from ADP and Pi

Question 2

What is the normal respiratory substance?

Answer 2

Glucose

Question 3

What else can be used a respiratory substance?

Answer 3

• Triglycerides

- Proteins

Question 4

Triglycerides as respiratory substances:

Answer 4

• Hydrolysed into glycerol and fatty acid
• Glycerol converted into pyruvate and enters respiration at the link reaction
• Fatty acid hydrolysed to form acetyl groups and enter respiration at Krebs cycle
• Three fatty acids in a single triglyceride can produce up to 50 acetyl groups that can form up to 500 ATP molecules

Question 5

Proteins as respiratory substances:

Answer 5

• Proteins digested to amino acids by proteases
• Amino acid deaminated
• Amino group converted into ammonia and then urea by ornithine cycle
• Remaining molecule converted to pyruvate, which enters respiration at the link reaction

Question 6

What are ketone bodies?

Answer 6

1. Ketone bodies are molecules that contain a ketone group
2. Produced when fatty acids are broken down for respiration during a long period of calorific restriction e.g. starvation
3. Brain also uses ketone bodies to synthesise fatty acids

Question 7

What is a RQ value?

Answer 7

Unitless value that is the ratio of the volume of CO2 produced to the volume of O2 produced, expressed as a single value

Question 8

How to calculate a RQ value?

Answer 8

RQ= CO2 produced/ O2 consumed

Question 9

Why do lipids have a smaller RQ value than carbohydrates?

Answer 9

• Lipids contain more C-H bonds than glucose so can produce more NADH and FADH and more ATPs
• Therefore, they need less oxygen during respiration