Alternative respiratory pathways

Question 1

When are fats used?

Answer 1

When carbohydrate in the body is running low.

Question 2

How do fats get used as an alternative respiratory pathway?

Answer 2

• hydrolysed to fatty acids and glycerol
• glycerol converted to triose phosphate, an intermediate in glycolysis
• long fatty acid chains are split into 2C acetate fragments and fed into Krebs cycle as AcCoA

Question 3

What do longer fatty acid chains have and what are the consequences?

Answer 3

• more carbon atoms so more CO2
• more hydrogen atoms so more NADH made so more ATP made
• more hydrogen atoms so more water is produced (metabolic water important for desert animals)

Question 4

When are proteins used as an alternative respiratory pathway?

Answer 4

When there are no carbohydrates and fats. The first place they are broken down from is the heart and kidney.

Question 5

How is protein used as an alternative respiratory pathway?

Answer 5

Proteins are hydrolysed into constituent amino acids
These are deaminated in the liver to make ammonia which breaks down to urea and Keto acids
The keto acids are either fed into glycolysis as pyruvate or into the Krebs cycle.