18.6 Respiratory Substrates

Question 1

What are respiratory substrates?

Answer 1

Organic molecules broken down in respiration

Question 2

Give an example of a respiratory substrate, other than glucose, and how it’s linked to respiration.

Answer 2

Triglycerides are hydrolysed into fatty acids which enter Krebs cycle via acetyl CoA and glycerol

Question 3

What can happen to glycerol in respiration?

Answer 3

First converted into pyruvate -> Undergoes oxidative decarboxylation -> Produces acetyl group, picked up by CoA -> Forms acetyl CoA

Question 4

Compare the energy output of carbs, lipids, proteins and alcohol.

Answer 4

Lipids = 2x as much energy as carbs
Alcohol = more than carbs, less than lipids
Proteins = same as carbs

Question 5

How happens to proteins in order for them to be able to generate ATP?

Answer 5

Proteins hydrolysed into amino acids

Amino acids deanimated before entering respiration as pyruvate

Question 6

What is the down side of using protein to generate ATP?

Answer 6

Steps to make protein usable require ATP, which reduces the net production of ATP.

Question 7

What does RQ stand for?

Answer 7

Respiratory Quotient

Question 8

How is RQ calculated?

Answer 8

CO2 produced
RQ = ————————————
O2 consumed

Question 9

Why do lipids produce more ATP than glucose?

Answer 9

Lipids have more C-H bonds

Question 10

What is the RQ for:

1. Carbohydrates
2. Proteins
3. Lipids

Answer 10

Carbs: 1.0
Proteins: 0.9
Lipids: 0.7

Question 11

What can we find out by calculating the RQ?

Answer 11

The type of substrate that’s being used for respiration

Question 12

What is the normal RQ range?

Answer 12

0.8-0.9