5.7.12 Respiratory Substrates

Question 1

What is the main respiratory substrate for aerobic respiration in most cells?

Answer 1

Glucose

Question 2

What are other substrates a cell may use to continue respiration when glucose is depleted?

Answer 2

• Other carbohydrates
• Lipids
• Proteins

Question 3

When are amino acids from proteins respired aerobically and why?

Answer 3

When all other substrates have been used up
This is because they often have essential functions elsewhere in the cell, and are required to make prtoeins which have structural and functional roles

Question 4

What is the energy value of carbohydrates?

Answer 4

15.8/kJg-1

Question 5

What is the energy value of lipids?

Answer 5

39.4/kJg-1

Question 6

What is the energy value of proteins?

Answer 6

17.0/kJg-1

Question 7

How are the differences in the energy values of substrates explained

Answer 7

By their molecular composition - specifically how many hydrogen atoms become available when the substrate molecules are broken down

Question 8

Describe the vital role of hydrogen atoms duyring respiration

Answer 8

More hydrogen atoms in a molecule

More hydrogen transported by NAD and FAD to mitochondrial membrane

Greater chemiosmotic/proton gradient

More ATP produced via chemiosmosis

Question 9

What is the benefit of a molecule having a higher hydrogen content?

Answer 9

A molecule with a higher hydrogen content will result in a greater proton gradient across the mitochondrial membrane which allows for the formation of more ATP via chemiosmosis

Question 10

Why do lipids have a high composition of hydrogen molecules?

Answer 10

As fatty acids in lipids are made up of long hydrocarbon chains with lots of hydrogen atoms. These hydrogen atoms are released when the lipid is broken down