Biochem- Cholesterol And Ketone Bodies Metabolism Flashcards
Where does Cholesterol synthesis take place?
Extra Mitochondrial in the liver, skin, intestine, adrenal cortex and testis.
Cholesterol synthesis is controlled by what rate limiting enzyme?
HMG CoA reductase.
What inhibits and promotes the rate limiting enzyme, HMG CoA reductase, of cholesterol synthesis?
Inhibited by — glucagon and glucocorticoids and bile salts.
Promoted by- insulin and thyroid hormones
State the enzyme and protein responsible for the transport and elimination of cholesterol from the body.
HDL (High density lipoprotein) and LCAT (Lecithin-cholesterol acyl transferase)
What is the total number of Acetyl CoA required of the synthesis of cholesterol?
18
Explain how ketone bodies are formed via prolonged starvation.
- Due to starvation, the body releases free fatty acids.
- The free fatty acids formed, enter the liver and going through b-oxidation in the mitochondria.
- Acetyl CoA and fatty acids is formed, however can not be used by the liver in the TCA cycle due to the lack of oxaloacetate.
- Due to this, the Acetyl CoA is converted to ketone bodes to be used by the body (meet energy requirements)
Explain how ketone bodies are formed via uncontrolled diabetes mellitus.
Due to the lack of insulin, carbohydrate metabolism in impaired.
2. The adipose tissue fat becomes the main energy source for the body causing the conversion of fat to Acetyl CoA to increase.
3. The mass production of Acetyl CoA causes it to accumulate leading into the Acetyl CoA to converted to ketone bodies.
Explain how ketone bodies are formed via feeding high fat diet.
- Excess breakdown of fatty acids lead to the increase in Acetyl CoA.
- Once the body meets the requirements for the amount of Acetyl CoA it needs, the remains excess is converted into ketone bodies.
- Ketone bodies are sent to various parts of the body to meet its energy requirements.
Where does the formation of ketone bodies take place?
Liver mitochondria.
Describe the formation of ketone bodies.
2 Acetyl CoA — thiolase — acetoacetyl Coa — HMG CoA synthase — b-oh b-methyl glutaryl CoA — HMG CoA lyase — Acetoactate + Acetyl CoA.
Acetoacetate is converted into CO2, Acetone and B- hydroxyl butyrate by (BHB dehydrogenase)
State the reason why the liver cannot be used in the utilization of ketones bodies (ketolysis.)
The lack of enzymes of thiophorase and CoA transferase, which is requires for the activation of ketone bodies, ketolysis.
Due prolong starvation and the utilization of ketones bodies, which compounds serves as the important source of energy for skeletal muscles, kidney and brain?
Acetoacetate and B-hydroxy butyrate.
State the factors that stimulate and inhibit ketogenesis.
Stimulate- glucagon, increased ratio of glucagon and insulin.
Inhibit - insulin.
