Lecture 6

Question 1

Glucose accounting

Answer 1

Glycerol (from lipolysis) is the only source of de nove gluconeogenesis. Only ~30g glucose from glycerol/day therefore more substrates needed for de novo glucose formation.

Question 2

Cons of proteolysis

Answer 2

• proteins cost lots of energy to make
• A lot of ATP is required to dispose of amine group
• Not all aa can be made into glucose
• many aa from proteolysis are burnt before release from tissue
• 2g of protein for 1g glucose
• Huge strain on protein

Brain needs 90g glucose/day so thats 180g protein from 6kg pool just for brain.

Question 3

Cons of using ketones

Answer 3

• Small and charged therefore, easily is lost in urine
• can spontaneously decarboxylate to acetone

Question 4

Time line

Answer 4

After 2 days: Brain uses 120g glucose/day. Protein loss >100g/day

After 3-4 days: Ketone bodies decreases brain’s need for glucose. Protein loss ~75g/day

By day 5: Brain using 30g glucose a day. No real protein loss.