Midterm II: Ketogenesis + breakdown (Ben) Flashcards Preview

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Flashcards in Midterm II: Ketogenesis + breakdown (Ben) Deck (11)
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1

What is the 1st step of ketogenesis?

(involving a β-oxidation enzyme)

Reactants?

Enzyme?

Products?

Condensation of two acetyl-CoA...

Reactants: 2x Acetyl-CoA

Enzyme: Thiolase (reverse rxn from β-oxidation)

Products: Acetoacetyl-CoA + CoA-SH

2

What is the 2nd step of ketogenesis, occuring after the reversal of the thiolase reaction?

Reactants?

Enzyme?

Products?

Condensation...

Reactants: Acetoacetyl-CoA + Acetyl-CoA + H2O

Enzyme: HMG-CoA Synthase

Products: HMG-CoA + CoA-SH

 

3

What is the 3rd step of ketogenesis, after condensation via HMG-CoA synthase?

Cleavage...

Reactants: HMG-CoA

Enzyme: HMG-CoA Lyase

Products: Acetoacetate + Acetyl-CoA

 

4

What are the two ketone bodies which are interconverted?

By which enzyme + coenzyme?

 

Acetoacetate + β-Hydroxybutyrate

via 

β-Hydroxybutyrate Dehydrogenase

( and NAD in the direction using β-OH Butyrate as a reactant)

5

What occurs to acetoacetate produced in ketogenesis?

it undergoes spontaneous decarboxylation

via acetoacetate decarboxylase

 

6

What controls the equilibrium between the two interconvertible ketone bodies?

Redox State

- more specifically [NAD+]/[NADH] ratio

- high NAD+ favors the dehydrogenation of β-hydroxybutyrate to acetoacetate

7

What tissues use ketone bodies during ketosis?

  1. cardiac muscle
  2. skeletal muscle
  3. brain
  4. kidney  (renal cortex)

8

What is the 1st step in the oxidation of ketone bodies by extrahepatic tissues?

Reactants?

Enzyme?

Product?

Activation via CoA...

Reactants: Acetoacetate + Succinyl-CoA

Enzyme: β-Ketoacyl-CoA Transferase

Product: Acetoacetyl-CoA + Succinate

9

What is the second step in oxidation of ketone bodies by extrahepatic tissues?

(resulting in a citric acid cycle intermediate)

Reactant?

Enzyme?

Product?

Cleavage...

Reactant: Acetoacetyl-CoA + CoA-SH

Enzyme: Thiolase

Product: 2 Acetyl-CoA

10

Since ketone bodies are generated starting from acetyl-CoA and then oxidized into acetyl-CoA for later use...

what is their purpose?

the are a transport form of acetyl groups

 

11

make some regulation cards

ok