Respiratory Substrates

Question 1

What substrates are used if glucose isn’t as the main respiratory substrate?

Answer 1

Carbs , lipids, proteins

Question 2

When are amino acids respired?

Answer 2

When all other substrates have been used up, they have essential

Question 3

How much energy is released for each respiratory substrate? (in kJ/g)

Answer 3

Carbs - 15.8
Lipids - 39.4
Protein - 17.0

Question 4

Why do some respiratory substrates release more energy than others when respired?

Answer 4

• Some substrates have more hydrogen atoms than others
• Substrates are broken down and hydrogen atoms become more available
• NAD and FAD become reduced
• H+ released is pumped across membrane into intermembrane space creating proton gradient
• Used in chemiosmosis to produce ATP
• So the more H atoms available, the more energy released
  (Greater H atom availability, greater proton gradient across mitochondrial membrane, so more ATP produced by chemiosmosis)
• Lipids have long fatty acid chains with many H atoms, hence lots of energy released when lipids are respired