Đề thi, bài tập trắc nghiệm online Hóa sinh lipid – Đề 4

1. Phospholipids are amphipathic molecules. What does 'amphipathic′ mean in this context?

A. They are soluble in water and lipids.

B. They have both hydrophilic and hydrophobic regions.

C. They are only found in animal cells.

D. They can only interact with proteins.

2. What is lipolysis and under what hormonal conditions is it stimulated?

A. Synthesis of fatty acids; stimulated by insulin.

B. Breakdown of triacylglycerols into fatty acids and glycerol; stimulated by glucagon and epinephrine.

C. Synthesis of triacylglycerols from fatty acids and glycerol; stimulated by glucagon.

D. Breakdown of cholesterol; stimulated by insulin.

3. Chylomicrons are lipoprotein particles. What is their primary function?

A. Transport cholesterol from the liver to peripheral tissues.

B. Transport dietary triacylglycerols from the intestine to other tissues.

C. Synthesize fatty acids in the liver.

D. Break down cholesterol in the blood.

4. How does insulin generally affect lipid metabolism?

A. Stimulates fatty acid oxidation and ketogenesis.

B. Inhibits fatty acid synthesis and triacylglycerol storage.

C. Stimulates fatty acid synthesis and triacylglycerol storage.

D. Has no significant effect on lipid metabolism.

5. What is the main function of Very-Low-Density Lipoproteins (VLDL)?

A. Transport dietary cholesterol.

B. Transport endogenous triacylglycerols from the liver to peripheral tissues.

C. Transport cholesterol to the liver.

D. Break down fats in adipose tissue.

6. What is the role of Acyl-CoA synthetase in fatty acid metabolism?

A. To synthesize fatty acids.

B. To activate fatty acids by attaching CoA for transport into mitochondria or other metabolic reactions.

C. To break down fatty acids into acetyl-CoA.

D. To incorporate fatty acids into triacylglycerols.

7. Sphingolipids are a class of membrane lipids. What is a key structural feature that distinguishes them from glycerophospholipids?

A. They contain fatty acids.

B. They have a phosphate group.

C. They contain a sphingosine backbone instead of glycerol.

D. They are amphipathic.

8. Glycolipids are lipids with attached carbohydrates. Where are they primarily found in eukaryotic cells?

A. Inner mitochondrial membrane

B. Cytosolic side of the plasma membrane

C. Extracellular side of the plasma membrane

D. Endoplasmic reticulum lumen

9. Which lipoprotein is primarily responsible for transporting cholesterol from peripheral tissues back to the liver for excretion or recycling?

A. VLDL

B. LDL

C. HDL

D. Chylomicrons

10. Which of the following enzymes is primarily responsible for digesting dietary triacylglycerols in the small intestine?

A. Amylase

B. Lipase

C. Protease

D. Nuclease

11. Ketogenesis occurs under certain metabolic conditions. What are ketone bodies?

A. Storage form of glucose.

B. Alternative fuel molecules synthesized from acetyl-CoA during fatty acid breakdown.

C. Building blocks for fatty acid synthesis.

D. Hormones derived from cholesterol.

12. What are prostaglandins and what are their general functions?

A. Structural lipids in cell membranes.

B. Hormone-like signaling molecules involved in inflammation, pain, and fever.

C. Energy storage molecules in adipose tissue.

D. Enzymes that digest dietary lipids.

13. What is the role of lipid rafts in cell membranes?

A. To store lipids for energy.

B. To increase membrane fluidity.

C. To organize membrane proteins and lipids, participating in cell signaling and trafficking.

D. To break down lipids for recycling.

14. Which cellular compartment is the primary site for fatty acid synthesis?

A. Mitochondria

B. Endoplasmic reticulum

C. Cytosol

D. Lysosomes

15. In fatty acid synthesis, what is the key precursor molecule from which fatty acids are built?

A. Glucose

B. Acetyl-CoA

C. Pyruvate

D. Amino acids

16. Low-Density Lipoproteins (LDL) are associated with increased risk of cardiovascular disease. Why?

A. They transport triacylglycerols to the liver.

B. They promote the removal of cholesterol from arteries.

C. They can deposit cholesterol in arterial walls, contributing to plaque formation.

D. They increase the levels of HDL cholesterol.

17. HMG-CoA reductase is a key enzyme in cholesterol synthesis. What is its role and regulation?

A. It is involved in fatty acid oxidation and is activated by insulin.

B. It is the rate-limiting enzyme in cholesterol synthesis and is inhibited by cholesterol.

C. It breaks down cholesterol and is activated by glucagon.

D. It is involved in triacylglycerol synthesis and is inhibited by fatty acids.

18. Lipids are a diverse group of biomolecules with various functions. Which of the following is NOT a primary function of lipids in living organisms?

A. Long-term energy storage

B. Structural components of cell membranes

C. Catalysis of biochemical reactions

D. Signaling molecules (hormones)

19. How do non-steroidal anti-inflammatory drugs (NSAIDs) like aspirin and ibuprofen reduce inflammation and pain?

A. By inhibiting the synthesis of cholesterol.

B. By inhibiting cyclooxygenase (COX) enzymes.

C. By increasing the synthesis of prostaglandins.

D. By blocking receptors for prostaglandins.

20. Which organ is the primary site for ketogenesis?

A. Brain

B. Muscle

C. Liver

D. Adipose tissue

21. Zellweger syndrome is a genetic disorder associated with defects in peroxisome biogenesis. Which aspect of lipid metabolism would be most directly affected in individuals with Zellweger syndrome?

A. Cholesterol synthesis

B. Mitochondrial fatty acid oxidation

C. Very-long-chain fatty acid (VLCFA) oxidation

D. Triacylglycerol digestion

22. Peroxisome proliferator-activated receptors (PPARs) are nuclear receptors that play a role in lipid metabolism. What is a general function of PPARs?

A. To inhibit fatty acid oxidation.

B. To regulate gene expression involved in lipid metabolism, particularly fatty acid oxidation and lipid uptake.

C. To directly synthesize fatty acids.

D. To transport lipids across cell membranes.

23. Eicosanoids are signaling lipids derived from polyunsaturated fatty acids. Which fatty acid is the primary precursor for many eicosanoids?

A. Palmitic acid

B. Oleic acid

C. Arachidonic acid

D. Stearic acid

24. Which type of lipid is characterized by a structure composed of four fused hydrocarbon rings?

A. Triacylglycerols

B. Phospholipids

C. Steroids

D. Fatty acids

25. Beta-oxidation is the primary pathway for fatty acid breakdown. What is the end product of beta-oxidation?

A. Glucose

B. Pyruvate

C. Acetyl-CoA

D. Fatty acids

26. Statins are a class of drugs commonly used to lower cholesterol levels. How do they work?

A. By increasing the absorption of cholesterol from the diet.

B. By inhibiting HMG-CoA reductase.

C. By promoting the synthesis of bile acids.

D. By increasing the activity of LDL receptors.

27. What is the role of bile salts in lipid digestion?

A. To hydrolyze triacylglycerols into fatty acids.

B. To emulsify dietary fats, increasing the surface area for lipase action.

C. To transport fatty acids into intestinal cells.

D. To synthesize triacylglycerols from fatty acids.

28. What is the primary difference between saturated and unsaturated fatty acids at the molecular level?

A. Number of carbon atoms

B. Presence of double bonds

C. Type of functional group

D. Overall molecular weight

29. What is the starting molecule for cholesterol synthesis?

A. Glucose

B. Acetyl-CoA

C. Fatty acids

D. Amino acids

30. Carnitine shuttle is crucial for fatty acid oxidation. What is its primary function?

A. To transport fatty acids from the cytosol into the mitochondrial matrix.

B. To synthesize carnitine in the liver.

C. To break down fatty acids in the cytosol.

D. To transport acetyl-CoA out of the mitochondria.