Flashcards in Ketone Bodies Deck (17)
Where are ketone bodies produced?
mitochondrial matrix of Liver cells( only when acetyl-CoA levels are higher than CTC capacity)
- allow for energy of peripheral tissues
High concentration of ketone bodies in the blood stream
- high in blood (ketonemia)
- high in urine (ketonuria)
Enzyme that catalyzes the 1st step of ketogenesis
Takes 2 acetyl CoA and forms Acetoacetyl-CoA
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
Enzyme that catalyses the 3rd step of ketogenesis
Cleaves HMG CoA to form Acetoacetate and acetyl CoA
* conducted ONLY in liver*
(B) HDB dehydra
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+
Ketone bodies are formed by what two molecules?
Acetoacetate and (b)-hydroxybutyrate
- acetoacetate can spontaneously form acetone
Advantage of ketone bodies over fatty acids
Ketone bodies are far more soluble and can move further in the body. (Fatty acid needs to use albumin as a transporter).
Action of forming 2 acetyl CoA from ketone bodies
(Occurs in peripheral cell matrix)
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*
2nd step of ketolysis
Binds a succinyl group from succinyl-CoA to acetoacetate to form
AA-CoA and succinate
4th step in ketolysis
Takes AA-CoA and generates 2 acetyl-CoA
How much ATP is formed from one (b)-HDB ketone body?
21.5 (transferase requires 1 ATP)
22.5-1 = 21.5
How much ATP is formed from 1 Acetoacetate ketone body?
19 (transferase requires 1 ATP)
20-1 = 19
Ketoacidosis is most common in what type of diabetes?
type 1 diabetes
What ketone body form is most favored under normal conditions?
b-HDB is more favored since NADH concentrations are favored over NAD+