Đề 11 – Bài tập, đề thi trắc nghiệm online Hóa sinh lipid

1. What is the primary function of waxes in biological systems?

A. Long-term energy storage

B. Structural component of cell membranes

C. Waterproofing and protection

D. Signaling molecules

2. Sphingolipids, like sphingomyelin and cerebrosides, are found in cell membranes, particularly abundant in nerve tissue. What is the characteristic structural feature of sphingolipids that distinguishes them from glycerophospholipids?

A. Glycerol backbone

B. Sphingosine backbone

C. Phosphate group

D. Fatty acid chains

3. What is the primary fate of glycerol produced from triglyceride hydrolysis in adipocytes?

A. It is used directly for energy production in adipocytes.

B. It is converted back into triglycerides and stored in adipocytes.

C. It is transported to the liver and used in gluconeogenesis.

D. It is excreted as waste product.

4. Which type of fatty acid contains no carbon-carbon double bonds?

A. Monounsaturated fatty acid

B. Polyunsaturated fatty acid

C. Saturated fatty acid

D. Omega-3 fatty acid

5. Which of the following statements about omega-3 and omega-6 fatty acids is correct?

A. Omega-3 fatty acids are saturated, while omega-6 fatty acids are unsaturated.

B. Both omega-3 and omega-6 fatty acids are essential fatty acids, meaning they must be obtained from the diet.

C. Omega-6 fatty acids are generally considered more beneficial for cardiovascular health than omega-3 fatty acids.

D. The `omega` designation refers to the number of carbon-carbon double bonds in the fatty acid chain.

6. Which lipoprotein is known as `bad cholesterol` due to its association with increased risk of atherosclerosis?

A. HDL (High-Density Lipoprotein)

B. LDL (Low-Density Lipoprotein)

C. VLDL (Very-Low-Density Lipoprotein)

D. Chylomicrons

7. Which of the following statements accurately describes the impact of unsaturation on the melting point of fatty acids?

A. Unsaturation increases the melting point because double bonds allow for tighter packing.

B. Unsaturation decreases the melting point because double bonds introduce kinks in the fatty acid chain, reducing packing efficiency.

C. Unsaturation has no significant effect on the melting point.

D. The effect of unsaturation on melting point depends on the length of the fatty acid chain.

8. Identify the correct order of lipoprotein densities, from least dense to most dense.

A. HDL < LDL < VLDL < Chylomicrons

B. Chylomicrons < VLDL < LDL < HDL

C. VLDL < Chylomicrons < LDL < HDL

D. LDL < HDL < Chylomicrons < VLDL

9. Lipoproteins are essential for transporting lipids in the bloodstream. Which lipoprotein is primarily responsible for transporting dietary triglycerides from the intestines to other tissues?

A. HDL (High-Density Lipoprotein)

B. LDL (Low-Density Lipoprotein)

C. VLDL (Very-Low-Density Lipoprotein)

D. Chylomicrons

10. Which of the following is NOT a ketone body?

A. Acetoacetate

B. β-hydroxybutyrate

C. Acetone

D. Oxaloacetate

11. Describe the function of flippases and floppases in cell membranes.

A. Both flippases and floppases transport lipids randomly across the membrane.

B. Flippases move lipids from the outer leaflet to the inner leaflet, while floppases move lipids from the inner leaflet to the outer leaflet.

C. Flippases move lipids from the inner leaflet to the outer leaflet, while floppases move lipids from the outer leaflet to the inner leaflet.

D. Both flippases and floppases maintain lipid asymmetry by preventing lipid movement across the membrane.

12. Beta-oxidation is a major metabolic pathway for fatty acid breakdown. Where does beta-oxidation primarily occur in eukaryotic cells?

A. Cytosol

B. Endoplasmic reticulum

C. Mitochondrial matrix

D. Golgi apparatus

13. What is the role of hormone-sensitive lipase (HSL) in lipid metabolism?

A. It synthesizes triglycerides in adipocytes.

B. It hydrolyzes triglycerides stored in adipocytes, releasing fatty acids and glycerol.

C. It transports fatty acids into mitochondria.

D. It emulsifies dietary fats in the intestine.

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

A. They directly catalyze fatty acid oxidation.

B. They regulate gene expression involved in lipid metabolism, glucose metabolism, and inflammation.

C. They transport fatty acids across the mitochondrial membrane.

D. They are involved in the synthesis of cholesterol.

15. Triacylglycerols are the main storage form of lipids in animals. What are the components of a triacylglycerol molecule?

A. One glycerol molecule and three fatty acids

B. Three glycerol molecules and one fatty acid

C. Two glycerol molecules and two fatty acids

D. One sphingosine molecule and three fatty acids

16. Which of the following is a common feature shared by all glycerophospholipids?

A. Sphingosine backbone

B. Ceramide linkage

C. Glycerol-3-phosphate backbone

D. Steroid ring structure

17. Which of the following enzyme classes is responsible for catalyzing the hydrolysis of ester bonds in triacylglycerols during lipid digestion?

A. Lipases

B. Proteases

C. Amylases

D. Nucleases

18. Eicosanoids are signaling lipids derived from polyunsaturated fatty acids. Which fatty acid is the primary precursor for most eicosanoids, including prostaglandins and leukotrienes?

A. Palmitic acid

B. Oleic acid

C. Linoleic acid

D. Arachidonic acid

19. Phospholipids are amphipathic molecules crucial for cell membrane structure. What does `amphipathic` mean in this context?

A. Having only hydrophobic regions

B. Having both hydrophilic and hydrophobic regions

C. Having only hydrophilic regions

D. Being soluble in both water and organic solvents

20. Which enzyme is the key regulatory enzyme in fatty acid synthesis?

A. Acetyl-CoA carboxylase

B. Fatty acid synthase

C. Carnitine acyltransferase I

D. HMG-CoA reductase

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

A. It hydrolyzes fatty acids from triglycerides.

B. It activates fatty acids by attaching them to Coenzyme A, forming fatty acyl-CoA.

C. It transports fatty acids across the mitochondrial membrane.

D. It synthesizes fatty acids from acetyl-CoA.

22. How does insulin regulate fatty acid metabolism?

A. Insulin promotes fatty acid breakdown and inhibits fatty acid synthesis.

B. Insulin inhibits both fatty acid breakdown and synthesis.

C. Insulin promotes fatty acid synthesis and inhibits fatty acid breakdown.

D. Insulin has no significant effect on fatty acid metabolism.

23. Carnitine shuttle is essential for the transport of fatty acids into mitochondria for beta-oxidation. What is the function of carnitine acyltransferase I?

A. It catalyzes the release of fatty acids from lipoproteins.

B. It catalyzes the transfer of fatty acids from cytosolic CoA to carnitine.

C. It catalyzes the oxidation of fatty acids in the mitochondrial matrix.

D. It catalyzes the synthesis of carnitine.

24. Lipids are a diverse group of biomolecules that are largely insoluble in water but soluble in organic solvents. Which of the following is NOT a primary function of lipids in living organisms?

A. Structural components of cell membranes

B. Long-term energy storage

C. Catalysis of biochemical reactions

D. Signaling molecules (hormones)

25. Ketogenesis is the process of producing ketone bodies. Under what physiological conditions is ketogenesis typically increased?

A. High glucose availability

B. Well-fed state

C. Prolonged fasting or uncontrolled diabetes

D. High insulin levels

26. What is the role of bile acids in lipid digestion and absorption?

A. They hydrolyze ester bonds in triglycerides.

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

C. They transport fatty acids into intestinal cells.

D. They synthesize triglycerides in the intestines.

27. What is the primary precursor molecule for fatty acid synthesis?

A. Glucose

B. Acetyl-CoA

C. Amino acids

D. Glycerol

28. Lipid rafts are specialized microdomains within cell membranes. What is the typical lipid composition that enriches lipid rafts?

A. Primarily unsaturated fatty acids and phospholipids

B. Primarily saturated fatty acids, cholesterol, and sphingolipids

C. Primarily glycolipids and triacylglycerols

D. Primarily phospholipids with short fatty acid chains

29. How does cholesterol affect the fluidity of cell membranes?

A. Cholesterol decreases membrane fluidity at all temperatures.

B. Cholesterol increases membrane fluidity at all temperatures.

C. Cholesterol has a bidirectional effect: it decreases fluidity at high temperatures and increases fluidity at low temperatures.

D. Cholesterol does not affect membrane fluidity.

30. Cholesterol is a steroid lipid that plays several important roles in the body. Which of the following is NOT a function of cholesterol?

A. Precursor for steroid hormones

B. Component of cell membranes, regulating fluidity

C. Primary source of energy for muscle contraction

D. Precursor for bile acids