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WVSOM -- Biochem
Oxidation of Ketone Bodies
Question | Answer |
---|---|
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 |