Ketone Bodies

Question 1

Where are ketone bodies produced?

Answer 1

mitochondrial matrix of Liver cells( only when acetyl-CoA levels are higher than CTC capacity)

• allow for energy of peripheral tissues

Question 2

Ketoacidosis

Answer 2

High concentration of ketone bodies in the blood stream

subsections are

• high in blood (ketonemia)
• high in urine (ketonuria)

Question 3

3-KA-CoA thiolase

Answer 3

Enzyme that catalyzes the 1st step of ketogenesis

Takes 2 acetyl CoA and forms Acetoacetyl-CoA

Question 4

HMG-CoA synthase

Answer 4

Enzyme that catalyzes the 2nd step of Ketogenesis.

Takes acetoacetyl-CoA and Acetyl-CoA and forms HMG-CoA

• HMG-CoA is a key intermediate in cholesterol biosynthesis

Question 5

HMG-CoA lyase

Answer 5

Enzyme that catalyses the 3rd step of ketogenesis

Cleaves HMG CoA to form Acetoacetate and acetyl CoA

• conducted ONLY in liver*

Question 6

(B) HDB dehydra

Answer 6

Enzyme that catalyses optional 4th reaction of Ketogenesis

Interchanges (b)-HDB and Acetoacetate

• going from acetoacetate -> (b)-HDB requires oxidation of NADH
• going from (b)-HDB -> acetoacetate requires reduction of NAD+

Question 7

Ketone bodies are formed by what two molecules?

Answer 7

Acetoacetate and (b)-hydroxybutyrate

• acetoacetate can spontaneously form acetone

Question 8

Advantage of ketone bodies over fatty acids

Answer 8

Ketone bodies are far more soluble and can move further in the body. (Fatty acid needs to use albumin as a transporter).

Question 9

Ketolysis

Answer 9

Action of forming 2 acetyl CoA from ketone bodies

Occurs in peripheral cell matrix

Question 10

BHB DHase

Answer 10

1st step of ketolysis
Converts (b) HDB into Acetoacetate and generates 1 NADH

• if ketone body arrives to peripheral cell as Acetoacetate already, this step is skipped*

Question 11

Transferase

Answer 11

2nd step of ketolysis

Binds a succinyl group from succinyl-CoA to acetoacetate to form

AA-CoA and succinate

Question 12

3-KA-CoA thiolase

Answer 12

4th step in ketolysis

Takes AA-CoA and generates 2 acetyl-CoA

Question 13

How much ATP is formed from one (b)-HDB ketone body?

Answer 13

21. 5 (transferase requires 1 ATP)

22. 5-1 = 21.5

Question 14

How much ATP is formed from 1 Acetoacetate ketone body?

Answer 14

19 (transferase requires 1 ATP)

20-1 = 19

Question 15

Ketoacidosis is most common in what type of diabetes?

Answer 15

type 1 diabetes

Question 16

What ketone body form is most favored under normal conditions?

Answer 16

b-HDB is more favored since NADH concentrations are favored over NAD+

Question 17

What happens when more Than normal acetyl-CoA is prevalent?

Answer 17

Is converted to ketone bodies