Đề 13 – Bài tập, đề thi trắc nghiệm online Hóa sinh lipid

1. Lipoproteins are responsible for transporting lipids in the blood. Which lipoprotein is primarily responsible for transporting dietary triacylglycerols from the intestines to other tissues?

A. High-density lipoproteins (HDL)

B. Low-density lipoproteins (LDL)

C. Very-low-density lipoproteins (VLDL)

D. Chylomicrons

2. Adipose tissue plays a key role in lipid storage and metabolism. What is the primary type of lipid stored in adipocytes (fat cells)?

A. Phospholipids

B. Cholesterol esters

C. Triacylglycerols (triglycerides)

D. Sphingolipids

3. Cholesterol is a steroid lipid with several important functions. Which of the following is NOT a function of cholesterol?

A. Precursor for steroid hormones

B. Component of cell membranes, modulating fluidity

C. Energy storage molecule in adipose tissue

D. Precursor for bile acids

4. Glycolipids are lipids with a carbohydrate attached. Where are glycolipids primarily located in eukaryotic cells?

A. Inner leaflet of the plasma membrane

B. Outer leaflet of the plasma membrane

C. Mitochondrial inner membrane

D. Endoplasmic reticulum membrane

5. Lipids are a diverse group of biomolecules. Which of the following is a defining characteristic common to all lipids?

A. They are polymers made of repeating monomer units.

B. They are primarily composed of carbon, hydrogen, and oxygen.

C. They are largely hydrophobic or amphipathic in nature.

D. They all contain phosphate groups.

6. Fatty acids are classified based on the presence and number of carbon-carbon double bonds. What is a saturated fatty acid?

A. A fatty acid containing one or more carbon-carbon double bonds.

B. A fatty acid containing only carbon-carbon single bonds.

C. A fatty acid containing a benzene ring.

D. A fatty acid that is essential for human health and must be obtained from the diet.

7. Which enzyme is the rate-limiting step in fatty acid synthesis?

A. Acetyl-CoA carboxylase

B. Fatty acid synthase

C. Carnitine acyltransferase I

D. HMG-CoA reductase

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

A. Cytoplasm

B. Endoplasmic reticulum

C. Mitochondrial matrix

D. Lysosomes

9. What are micelles in the context of lipid absorption?

A. Large fat globules in the small intestine before emulsification.

B. Vesicles that transport lipids from the endoplasmic reticulum to the Golgi apparatus.

C. Small aggregates of bile acids, fatty acids, and monoacylglycerols that facilitate lipid absorption across intestinal cells.

D. Lipoprotein particles that transport lipids in the blood.

10. Which of the following conditions would generally lead to increased lipogenesis (fatty acid synthesis) in the liver?

A. Prolonged fasting

B. High carbohydrate diet

C. Insulin deficiency

D. Increased glucagon levels

11. Triacylglycerols (triglycerides) are the main storage form of lipids. What are they composed of?

A. Two fatty acids and one glycerol molecule.

B. Three fatty acids and one glycerol molecule.

C. Four fatty acids and one glycerol molecule.

D. Three fatty acids and one sphingosine molecule.

12. Phospholipids are major components of cell membranes. What is the basic structure of a phospholipid?

A. Glycerol, two fatty acids, and a phosphate group.

B. Sphingosine, two fatty acids, and a phosphate group.

C. Glycerol, three fatty acids, and a phosphate group.

D. Cholesterol, two fatty acids, and a phosphate group.

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

A. To directly catalyze lipid synthesis reactions.

B. To transport lipids across cellular membranes.

C. To regulate gene expression involved in lipid metabolism.

D. To degrade lipids in lysosomes.

14. Which of the following lipoproteins is considered `good cholesterol` and is involved in reverse cholesterol transport?

A. Chylomicrons

B. Low-density lipoproteins (LDL)

C. Very-low-density lipoproteins (VLDL)

D. High-density lipoproteins (HDL)

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

A. To hydrolyze triacylglycerols into fatty acids and glycerol.

B. To emulsify dietary lipids in the small intestine, increasing surface area for enzyme activity.

C. To transport fatty acids across the intestinal epithelial cells.

D. To synthesize triacylglycerols from absorbed fatty acids in the liver.

16. Sphingolipids are a class of lipids found in cell membranes, particularly in nerve tissue. What is the characteristic backbone of sphingolipids?

A. Glycerol

B. Sphingosine

C. Cholesterol

D. Isoprene

17. How many rounds of beta-oxidation are required to completely oxidize a 16-carbon saturated fatty acid?

A. 7

B. 8

C. 16

D. 15

18. Which enzyme is responsible for hydrolyzing cholesterol esters during lipid digestion?

A. Pancreatic lipase

B. Phospholipase A2

C. Cholesterol esterase

D. Lipoprotein lipase

19. Which of the following is an essential fatty acid for humans, meaning it cannot be synthesized by the body and must be obtained from the diet?

A. Palmitic acid

B. Oleic acid

C. Linoleic acid (omega-6)

D. Stearic acid

20. Ketogenesis is the process of producing ketone bodies. Under what metabolic condition is ketogenesis significantly increased?

A. High glucose availability

B. Well-fed state with balanced diet

C. Prolonged fasting or uncontrolled diabetes

D. High insulin levels

21. Eicosanoids are signaling lipids derived from fatty acids. Which fatty acid is the primary precursor for most eicosanoids, such as prostaglandins and leukotrienes?

A. Palmitic acid

B. Stearic acid

C. Arachidonic acid

D. Oleic acid

22. Abetalipoproteinemia is a genetic disorder characterized by the inability to produce apolipoprotein B. Which lipoprotein assembly is most directly affected in this condition?

A. High-density lipoproteins (HDL)

B. Low-density lipoproteins (LDL)

C. Very-low-density lipoproteins (VLDL) and chylomicrons

D. Intermediate-density lipoproteins (IDL)

23. Glycerol-3-phosphate dehydrogenase is an enzyme important in both triacylglycerol synthesis and glyceroneogenesis. What is the substrate for glycerol-3-phosphate dehydrogenase?

A. Glycerol

B. Dihydroxyacetone phosphate (DHAP)

C. Glycerol-3-phosphate

D. Fatty acyl-CoA

24. Which of the following is NOT a major function of lipids in biological systems?

A. Long-term energy storage

B. Structural component of cell membranes

C. Catalysis of biochemical reactions

D. Cell signaling and communication

25. Hormone-sensitive lipase (HSL) is a key enzyme in lipolysis. What is the primary function of hormone-sensitive lipase?

A. To synthesize triacylglycerols from fatty acids and glycerol.

B. To hydrolyze triacylglycerols into fatty acids and glycerol in adipocytes.

C. To transport fatty acids into mitochondria for beta-oxidation.

D. To synthesize cholesterol esters.

26. Carnitine shuttle is essential for fatty acid oxidation. What is its primary function?

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

B. To transport acetyl-CoA from the mitochondrial matrix to the cytoplasm.

C. To synthesize carnitine from fatty acids.

D. To inhibit beta-oxidation when fatty acid levels are low.

27. Pancreatic lipase is a key enzyme in digestion. What is the primary substrate of pancreatic lipase?

A. Phospholipids

B. Cholesterol esters

C. Triacylglycerols

D. Glycolipids

28. Leukotrienes are a class of eicosanoids involved in inflammation and allergic reactions. Which enzyme is the key enzyme in the synthesis of leukotrienes from arachidonic acid?

A. Cyclooxygenase (COX)

B. Lipoxygenase (LOX)

C. Phospholipase A2 (PLA2)

D. Acyltransferase

29. Lipid rafts are microdomains within cell membranes. What is the characteristic lipid composition of lipid rafts?

A. Primarily composed of glycerophospholipids and unsaturated fatty acids.

B. Enriched in cholesterol and sphingolipids with saturated fatty acids.

C. Exclusively composed of triacylglycerols.

D. Characterized by the absence of lipids, primarily protein-based.

30. Statins are a class of drugs commonly used to lower cholesterol levels. What is the primary mechanism of action of statins?

A. Inhibition of intestinal cholesterol absorption.

B. Inhibition of HMG-CoA reductase, a key enzyme in cholesterol synthesis.

C. Increased excretion of bile acids.

D. Increased activity of lipoprotein lipase.