Question

During ketogenesis, the liver synthesizes ketone bodies that can be used as an energy source. Put the following statements regarding ketogenesis in the correct order, beginning with a stimulus for ketogenesis.
a. Low glucose levels stimulate the breakdown of fatty acids to acetyl-Cox
b. HMG-CoA Loses acetyl-CoA forming a four-carbon ketone body.
c. A condensation reaction with acetyl-CoA produces the six-carbon HMG-CoA.
d. Two acetyl-CoA condense to form the four-carbon acetoacetyl-CoA.
e. 3-Hydroxybutyrate and acetoacetate can cross tie blood-brain barrier to provide fuel for the brain,

Answer 1

The following statements regarding ketogenesis in the correct order, beginning with a stimulus for ketogenesis:

a) Low glucose levels stimulate the breakdown of fatty acids to acetyl-CoA.

d. Two acetyl-CoA condense to form the four-carbon acetoacetyl-CoA.

c. A condensation reaction with acetyl-CoA produces the six-carbon HMG-CoA.

b)  HMG-CoA Loses acetyl-CoA forming a four-carbon ketone body.

e). 3-Hydroxybutyrate and acetoacetate can cross tie blood-brain barrier to provide fuel for the brain.

Explanation:

Ketogenesis takes place in mitochondria of the hepatic cells when energy source as glucose is depleted.

When carbohydrate is in not present in the cell the AMPK regulatory protein gets activated which slow downs lipogenesis and activates malonyl CoA decarboxylase enzyme.

Ketogenesis take splace in following steps:

1) When no or low carbohydrate is there the the fatty acid breakdown takes place.

2)  Oxidation of fatty acid takes place to form acetyl CoA takes place.

3) Acetoacetylyl CoA formation takes place by enzyme thiolase action in which 2 acetyl CoA reacts.

4) A six carbon compound named 3-hydroxy-3-methylglutaryl-CoA takes place place. The enzyme working is HMG CoA synthase.

5)  A compound gets form which is Acetoacetate by releasing an acetyl CoA by the actIon of enzyme HMG CoA lyase.

6). Acetoacetate and 3-hydroxybutarate  are used to provide energy to the body and the brain.

The acetyl CoA released enters the TCA cycle.