Biochemistry Exam Ii: Ketone Body Synthesis

Front 1

Why do ketone body synthesis?

Back 1

Water soluble derivative of lipids called ketone bodies

From excess acetyl CoA when fat breakdown predominates.

Major fuel source of brain, if necessary

Front 2

Where does Ketone body synthesis occur?

Back 2

Liver mitochondiria

Front 3

Conditions in which ketone bodies are produced

Back 3

-Entry of Acetyl CoA into TCA depends on OAA
-OAA kept in low concentrations because it is immediately used by GNG
-When this happenes, OAA will not go to the TCA cycle

Front 4

What happens when B-oxidation of FA occurs to form acetyl CoA, but OAA is not available (doing GNG)?

Back 4

acetyl CoA diverted to form 3 ketone bodies: acetoacetate, 3-hydroxybutyrate, and acetone

Front 5

1. 2 acetyl CoA's attach end-to-end-->acetoacetyl CoA

Back 5

B-ketothiolase
CO2 removed
Unfavorable

Front 6

2. A third acetyl CoA hooks onto acetoacetyl CoA-->3-hydroxy-3-methylglutaryl CoA (HMG-CoA)

Back 6

HMG-CoA Synthase
Cleavage of this thioester linkage drives the unfavorable rxn forward

Front 7

3. Acetyl CoA is clipped off
HMG-CoA-->acetoacetate

Back 7

HMG-CoA Lyase

Front 8

4. Acetoacetate spontaneously forms --> acetone or B-hydroxybutyrate

Back 8

Spontaneous decarboxylation to form acetone

Produce NAD upon conversion to B-hydroxybutyrate

Front 9

What happens under normal conditions, when we break down fats?

Back 9

Acetyl CoA combines with OAA--citrate--TCA

Front 10

What happenes under diabetic/starving conditions?

Back 10

Pyruvate --> OAA by pyruvate carboxylase

OAA-->malate and transported out of the mitochondria

Malate --> OAA and goes to GNG

Acetyl CoA cannot combine with OAA because OAA is so quickly converted to malate