Question

Which of the following statements about the triacylglycerols stored in adipose tissue is correct?

a. they are hydrolyzed to form directly fatty acids and dihydroxyacetone

b. they are hydrolyzed by a lipase that is activated by acetylation

c. they release fatty acids that can be oxidized to pyruvate to provide energy to the cell

d. they can yield a precursor of glucose

		e. they are mobilized by insulin please explain!!

Answer 1

Ans: Triacylglycerols or the triglycerides as they are commonly called, are high energy lipid products of fatty acids.They contain 3 fatty acids that are esterified with a backbone of glycerol.They are stored in the adipose tissue and is released as and when required.

Now Let us examine each answer option and see whether they are correct statement or not based on further information about Triacylglycerols and their synthesis.

(a)They are hydrolyzed to form directly fatty acids and dihydroxyacetone - Production of energy from Triacylglycerols starts with its hydrolysis,which yields Free fatty acids and glycerol.

Thus, the above statement is incorrect and hence cannot be the correct answer option.

(b)They are hydrolyzed by a lipase that is activated by acetylation - When a high energy demand arises in the body, hydrolysis of triacylglycerol is carried out in the adipose tissue by the help of enzyme lipase,resulting into the release of free fatty acids and glycerol.This is because of the activation of  Gs-coupled receptors by catecholamines that increases the adipocyte lipolysis due to high energy demand by the body.

Thus, the above statement is incorrect and hence cannot be the correct answer option.

(c)They release fatty acids that can be oxidized to pyruvate to provide energy to the cell - Hydrolysis of triacylglycerols releases free fatty acids and glycerols,out of which the free fatty acids are adsorbed to serum albumin,after being travelled through the bloodstream.

Thus, the above statement is incorrect and hence cannot be the correct answer option.

(d)They can yield a precursor of glucose - The glycerols released by the hydrolysis of triacylglycerols is transported to the liver where by the action of enzymes- glycerol kinase and glycerol-3-phosphate dehydrogenase,it is sent to the glycolytic pathway to form Glyceraldehyde-3-phosphate.This can be then used as a source of glucose or can be used as an intermediate of TCA cycle,after being converted into phosphoenolpyruvate.In other words, hydrolysis of triacylglycerols yield a precursor of glucose.

Thus, the above statement is correct and hence the answer option.

(e)They are mobilized by insulin - It is mobilized when the levels of glucagon and adrenaline hormones present in the blood increases due to high energy requirement by the body.The increased leves make them bind to specific receptors on the adipose tissue surface.This binding creates a cascade of reactions in cells which then activates the enzyme lipase to hydrolyze the triacylglycerols.

Thus, the above statement is incorrect and hence cannot be the correct answer option.