This set of Life Sciences Multiple Choice Questions & Answers (MCQs) focuses on “Lipid Metabolism”.
1. Name the most active organs in the animal body which have the ability to synthesize triacylglycerol?
a) Spleen
b) Kidney
c) Liver and intestines
d) Adipose tissues
View Answer
Explanation: In general, all plants and animals have the ability to synthesize triacylglycerol (TAG). In animals, liver and intestines are two most active sites for TAG synthesis. Adipose tissues are the storage site for fat.
2. Triacylglycerol stored in the body as cytoplasmic lipid droplets.
a) True
b) False
View Answer
Explanation: Triacylglycerol is stored as the cytoplasmic lipid droplets like fat globules, oil bodies, lipid particles, adiposomes etc. These triacylglycerols are enclosed by a monolayer of phospholipids and hydrophobic proteins.
3. Which of the following pathway is not used for triacylglycerol synthesis?
a) Glycerol 3-phosphate pathway
b) Glyoxylate pathway
c) Monoacylglycerol pathway
d) Kennedy pathway
View Answer
Explanation: Except glyoxylate pathway, all three pathways have been used for the synthesis of triacylglycerol. Kennedy pathway and glycerol 3-phosphate pathway are same which predominates in the liver and adipose tissue while the monoacylglycerol pathway used in intestines.
4. Which of the following enzyme is not used in the synthesis of triacylglycerol?
a) Glycerol-3-phosphate acyltransferase
b) Acylglycerophophate acyltransferase
c) Phosphatidic acid phosphohydrolase
d) Glycogen phosphorylase
View Answer
Explanation: Triacylglycerol biosynthetic pathway involves the formation of triacylglycerol by glycerol-3-phosphate. It involves four steps catalyzed by all the above enzymes except glycogen phosphorylase. The fourth enzyme is Diacylglycerol acyltransferase which converts diacylglycerol to triacylglycerol.
5. What is lipolysis?
a) Hydrolysis of triacylglycerol
b) Formation of lipids
c) Breakdown of ketone bodies
d) Formation of ketone bodies
View Answer
Explanation: Hydrolysis of triacylglycerol by lipase is called lipolysis. Triacylglycerol stored in adipose tissues of animals in an insoluble form where they constantly synthesized and broken down again.
6. Which of the following hormone is not used in the hydrolysis of triacylglycerol into the fatty acids in adipose tissues?
a) Epinephrine
b) Norepinephrine
c) Glucagon
d) Insulin
View Answer
Explanation: Triacylglycerols are converted to free fatty acids and glycerol under the influence of certain hormones. Hormones which control hydrolysis of the TAG are epinephrine, norepinephrine, and glucagon.
7. Mark the INCORRECT statement about the bile salt.
a) These are detergent substances
b) Stored in the gallbladder
c) It is hydrophobic in nature
d) It is made up of cholic acid
View Answer
Explanation: The surface of bile salt molecule is both hydrophobic and hydrophilic in nature. Bile salts are made up of bile acids, synthesized in the liver and stored in the gallbladder. It facilitates the digestion of lipids.
8. Triacylglycerol packed with the apolipoprotein and cholesterol in lipoprotein aggregate is called_________
a) Chylomicrons
b) VLDL
c) HDL
d) LDL
View Answer
Explanation: Triacylglycerol packed with cholesterol and apolipoprotein and forms chylomicron which moves through lymphatic system where lipoprotein lipase breaks it in fatty acids and glycerol. Finally, fatty acids absorbed as a fuel or stored.
9. What is the outcome of the accumulation of acetyl-CoA in the mitochondria of the liver?
a) It is used as an energy source
b) It has broken down in to free fatty acids
c) It gets converted to oxaloacetate
d) It forms ketone bodies
View Answer
Explanation: Most of the acetyl-CoA has been used by citric acid cycle but during starvation acetyl-CoA accumulated in the mitochondria of liver and forms ketone bodies. Formation of ketone bodies by acetyl-CoA is known as ketogenesis.
10. Name the energy source of the brain during starvation?
a) Fat
b) Ketone bodies
c) Protein
d) Lipids
View Answer
Explanation: In the absence of glucose or during prolonged starvation, the brain gets energy from ketone bodies by converting it to acetyl-CoA. This mechanism is absent in liver so, it cannot utilize ketone bodies as an energy source.
11. What is the biosynthetic source of all steroid hormones?
a) Cholesterol
b) Ketone bodies
c) Carbohydrate
d) Protein
View Answer
Explanation: Pregnenolone is the precursor of all steroid hormones which is synthesized by cholesterol and catalyzed by desmolase enzyme. It involves the shortening of hydrocarbon chain of cholesterol and hydroxylation of steroid nucleus.
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