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Biochemistry - 3 Questions

1
Biochemistry

Which of the following enzymes is active in adipocytes following a heavy meal?

1) Glycogen phosphorylase
2) Glycerol kinase
3) Hormone-sensitive triacylglyceride lipase
4) Phosphatidate phosphatase

📝 Explanation:

The enzyme phosphatidate phosphatase converts phosphatidic acid to diacylglycerol during synthesis of triacylglycerides.

The function of adipose tissue is the storage of fatty acids as triacylglycerols in times of plenty and the release of fatty acids during times of fasting or starvation.

Fatty acids taken in by adipocytes are stored by esterification to glycerol-3-phosphate. Glycerol-3-phosphate is derived almost entirely from the glycolytic intermediate dihydroxyacetone phosphate through the action of glycerol-3-phosphate dehydrogenase. Glycolytic enzymes are active in adipocytes during triglyceride synthesis, but those of glycogen degradation (low levels in adipocytes) and gluconeogenesis (ie, glucose-6-phosphatase) are not.

Glycerol kinase is not present to any great extent in adipocytes, so that glycerol freed during lipolysis is not used to reesterify the fatty acids being released.

The enzyme triacylglyceride lipase is turned on by phosphorylation by a cyclic AMP-dependent protein kinase following epinephrine stimulation.

2
Biochemistry
The lipids associated with very low density lipoprotein 1. are usually linked covalently to apoproteins. 2. belong primarily to the phosphatidylcholine class. 3. incorporate fatty acids that are synthesized in the liver. 4. reflect, in general, the types of lipids found in the diet.

📝 Explanation:

VLDL is a lipoprotein particle synthesized in the liver and secreted into the bloodstream to transport endogenously synthesized triglycerides and cholesterol to peripheral tissues. The triglycerides in VLDL are derived from fatty acids synthesized in the liver, and the cholesterol is derived from both dietary sources and de novo synthesis in the liver. They are not usually linked covalently to apoproteins (Answer 1), nor do they primarily consist of phosphatidylcholine (Answer 2). While the types of lipids found in the diet (Answer 4) can influence the liver's synthesis of VLDL, the statement does not accurately describe the direct composition of VLDL.

3
Biochemistry
Glycine is a: 1. Glycogenic amino acid, only 2. Ketogenic only 3. Glucogenic and ketogenic 4. Since It Is optically inactive therefore none of the above

📝 Explanation:

Glycine is a Glycogenic amino acid, only

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