Ketosis + Ketone bodies

Question 1

Sometimes acyl-CoA is used to synthesise ketone bodies

Answer 1

Acetoacetate, acetone, D-beta-hydroxybutyrate are called ketone bodies
Instead of entering TCA, Acyl-CoA is sometimes used to produce ketone bodies
Generating ketone bodies-ketogenesis-is esp common in liver
Ketogenesis produces acetoacetate and D-hydroxybutyrate

Question 2

During starvation, ketone bodies become major energy source

Answer 2

body and brain adapt to ketones as fuel
fat reserves are used to generate ketone bodies
(Fatty acids cannot cross Bloodbrain barrier–> cannot be used as fuel)

Question 3

Ketogenesis pathway

Answer 3

1. Claisen ester condensation of 2 molecules of acetyl-CoA (Thiolase)
2. Claisen-like condensation (also acyl-thioester enz intermediate) to form beta-hydroxy-beta-methylgutaryl-CoA
3. Cleavage rxn to generate acetoacetate and acetyl-CoA

Question 4

Generation of acetate and D-Beta-hydroxybutyrate in liver

Answer 4

acetoacetate–(NADH->NAD+)—[beta-hydroxybutyrate d/h]–>D-beta-hydroxybutyrate
OR
acetoacetate—–>acetone (converted spontaneously)

Question 5

Conversion of ketone bodies to acetyl-CoA

Answer 5

-occurs in peripheral tissues using ketone bodies as alternative fuel