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WVSOM -- Biochem

Oxidation of Ketone Bodies

QuestionAnswer
Ketone Bodies are produced in the ________ Liver
Is ketone body production a fed state or a fasted state event? Fasted State
Are ketones toxic? Not as long as they can be used.
Why is ketone body production and use in a fasted state? Liver Beta oxidizes esxcess fatty acids mobilized from adipocytes in teh fasted state. Acetyl-CoA produced by B oxidation is the "excess" carbon for hepatic ketone body synthesis
What produces Acetyl CoA for ketone production? B-Oxidation and ketogenic amino acid catabolism
Why can't the liver use all the acetyl CoA it produces in the fasted state? B-oxidation produces more Aceytl CoA than can be used
Why can't the liver use all of the acetyl CoA it produces in the Fasted Stated The liver must devote significant oxaloacetate to gluconeogenesis so this limites the TCA cycle activity.
What does teh liver obtain from its B-oxidation of excess fatty acids? FADH2 AND NADH are used by the liver without involvement of teh TCA cycle. Can go straight to oxidative phosphorylation
NADH may provide "___________" for mitochondrial malate dehydrogenase’s production of malate from oxaloacetate. reducing power
What does the body do with excess acetyl CoA carbons the liver cannot catabolize? The liver converts it to ketone bodies.
What organs import ketone bodies? heart, kidney and skeletal muscle
Why can high energy demand organs catabolize ketone bodies? they do not have the limit on their TCA cycle activity that hepatocytes do
Can the liver use ketone bodies? no
Can acetoacetyl CoA cross the plasma membrane? No
What CoA is at a branch point of the ketone body synthesis pathway? HMG CoA
Acetoacetate is reduced to B-hydroxybutyrate
What reduces acetaoacetate to b-hydroxybutyrate β-hydroxybutyrate dehydrogenase
What happens to acetoacetate when it remains in the blood stream? it is converted non-enzymatically to acetone
How is the acetone removed from the body? exhaled
Two ketone bodies increases the rate of ______________ export from the liver and their solubility in the blood stream
Ketone Bodies are known as a-b-hydroxybutyrate
Ketone body catabolism b-hydroxybutyrate is converted to acetoacetate
What catalyzes ketone body catabolism b-hydroxybutyrate dehydrogenase
Starting Materials of Ketone production Acetyl CoA
Source of ketone starting material b-oxidation
Products of Ketone Body Production Acetoacetate (produced first) β-Hydroxybutyrate (produced by oxidizing acetoacetate)
Intermediate at the branch point of cholesterol HMG-CoA
Can the brain catabolize ketone bodies? Yes, but only after a complete fast of several days
Can red blood cells ever catabolize ketone bodies? No, they do not have mitochondria
Can red blood cells ever catabolize ketone bodies? No
What cells besides RBC cannot use ketones? None, almost all other types of cells can catabolize ketone bodies, just in a much lesser extent
When does catabolism of ketone bodies increase? As ketone body levels in the blood stream rise with increased duration of a fast.
When does the brain use ketone bodies? only after a complete fast of 3-4 days
Is the presence of ketone bodies in the blood stream always a pathological event? no
When is the presence of ketone bodies in teh blood stream a pathological event? When hepatic ketone body production exceeds extrahepatic cell ketone body use
How does the body attempt to limit ketoacidosis? Kidneys begin to excrete ketone bodies. Acetoacetate is nonenzymatically converted to acetone and exhaled.
What exacerbates ketoacidosis? presence of high serum levels of lactate and/or uric acid
Is ketoacidosis necessarily associated with diabtes? No
Causes of Ketoacidosis Occurs in unregulated diabetic when lack of insulin mimics the fasted state. Occurs in longer fasts/starvation states in nondiabetics
Created by: tjamrose