1. What is the role of phospholipase A2 (PLA2) in lipid metabolism?
A. Synthesizing phospholipids
B. Hydrolyzing fatty acids from phospholipids, particularly arachidonic acid
C. Transporting phospholipids between organelles
D. Degrading sphingolipids
2. Lipoproteins are responsible for transporting lipids in the blood. Which lipoprotein is primarily responsible for transporting dietary triglycerides from the intestines to other tissues?
A. High-density lipoprotein (HDL)
B. Low-density lipoprotein (LDL)
C. Very-low-density lipoprotein (VLDL)
D. Chylomicrons
3. Which of the following is a precursor for the synthesis of eicosanoids, such as prostaglandins and leukotrienes?
A. Palmitic acid
B. Stearic acid
C. Arachidonic acid
D. Linoleic acid
4. Which of the following lipoproteins is often referred to as `bad cholesterol′ due to its association with increased risk of cardiovascular disease?
A. High-density lipoprotein (HDL)
B. Low-density lipoprotein (LDL)
C. Very-low-density lipoprotein (VLDL)
D. Chylomicrons
5. Which enzyme is primarily responsible for hydrolyzing triglycerides in the small intestine?
A. Lipoprotein lipase
B. Gastric lipase
C. Pancreatic lipase
D. Hormone-sensitive lipase
6. What is the significance of omega-3 and omega-6 fatty acids?
A. They are saturated fatty acids essential for energy storage.
B. They are essential polyunsaturated fatty acids that the human body cannot synthesize.
C. They are monounsaturated fatty acids primarily used for membrane structure.
D. They are precursors for cholesterol synthesis.
7. Triacylglycerols (triglycerides) are the main storage form of lipids in the body. What are the building blocks of a triacylglycerol molecule?
A. Two fatty acids and one phosphate group
B. Three fatty acids and one glycerol molecule
C. One fatty acid and three glycerol molecules
D. Steroid rings and fatty acids
8. Which of the following is an example of a sphingolipid?
A. Triglyceride
B. Phosphatidylcholine
C. Ceramide
D. Cholesterol
9. Which enzyme catalyzes the committed step in fatty acid synthesis?
A. Acetyl-CoA carboxylase
B. Fatty acid synthase
C. Citrate synthase
D. Pyruvate dehydrogenase
10. What is the end product of fatty acid synthesis?
A. Cholesterol
B. Palmitic acid (a saturated fatty acid)
C. Oleic acid (an unsaturated fatty acid)
D. Acetyl-CoA
11. Lipids are a diverse group of biomolecules. Which of the following is a primary function of lipids in living organisms?
A. Catalyzing biochemical reactions
B. Storing genetic information
C. Providing structural components of cell membranes and energy storage
D. Transporting oxygen in the blood
12. What is the role of acyl-CoA synthetase in fatty acid metabolism?
A. To hydrolyze fatty acids from triglycerides
B. To activate fatty acids by attaching CoA before beta-oxidation
C. To synthesize fatty acids from acetyl-CoA
D. To transport fatty acids into the mitochondria
13. Cholesterol is a crucial lipid with multiple roles. Which of the following is NOT a function of cholesterol in animals?
A. Precursor for steroid hormones
B. Component of cell membranes to modulate fluidity
C. Precursor for bile acids
D. Primary energy storage molecule
14. Phospholipids are major components of cell membranes. What is the key structural feature of phospholipids that allows them to form lipid bilayers in aqueous environments?
A. They are composed entirely of hydrophobic fatty acid tails.
B. They have a hydrophilic head and hydrophobic tails.
C. They contain glycerol but no fatty acids.
D. They are made up of steroid rings.
15. Which type of fatty acid contains only single bonds between carbon atoms and is typically solid at room temperature?
A. Unsaturated fatty acid
B. Polyunsaturated fatty acid
C. Saturated fatty acid
D. Monounsaturated fatty acid
16. Which hormone primarily stimulates lipogenesis (fatty acid synthesis)?
A. Glucagon
B. Epinephrine
C. Insulin
D. Cortisol
17. Statins are a class of drugs commonly used to lower cholesterol levels. What is the mechanism of action of statins?
A. They inhibit the absorption of cholesterol from the intestine.
B. They increase the excretion of bile acids.
C. They inhibit HMG-CoA reductase, a key enzyme in cholesterol synthesis.
D. They promote the breakdown of LDL cholesterol.
18. Which of the following conditions would promote fatty acid oxidation and inhibit fatty acid synthesis?
A. High carbohydrate intake
B. High insulin levels
C. Fasting or starvation
D. Excess calorie consumption from fat
19. What is the primary mechanism by which orlistat, a weight-loss drug, works?
A. Inhibiting fatty acid synthesis
B. Increasing fatty acid oxidation
C. Inhibiting pancreatic lipase activity
D. Promoting cholesterol excretion
20. Beta-oxidation is a metabolic process that breaks down fatty acids. Where in the cell does beta-oxidation primarily occur?
A. Cytosol
B. Endoplasmic reticulum
C. Mitochondrial matrix
D. Lysosomes
21. Which of the following is NOT a lipid-soluble vitamin?
A. Vitamin A
B. Vitamin B
C. Vitamin D
D. Vitamin K
22. What is the primary function of waxes in biological systems?
A. Energy storage
B. Structural support and water repellency
C. Cell signaling
D. Enzyme catalysis
23. What is the function of carnitine in fatty acid metabolism?
A. To activate fatty acids for beta-oxidation
B. To transport fatty acids into the mitochondrial matrix for beta-oxidation
C. To synthesize fatty acids in the cytosol
D. To regulate cholesterol synthesis
24. What is the role of bile salts in lipid digestion?
A. To hydrolyze triglycerides into fatty acids and glycerol
B. To emulsify dietary fats, increasing the surface area for lipase action
C. To transport fatty acids into intestinal cells
D. To synthesize triglycerides in the liver
25. Which organ is the primary site for cholesterol synthesis in the human body?
A. Brain
B. Liver
C. Kidney
D. Skeletal muscle
26. How do trans-fatty acids differ from cis-fatty acids in terms of their structure and health effects?
A. Trans-fatty acids have double bonds in the cis configuration and are healthier than cis-fatty acids.
B. Trans-fatty acids have double bonds in the trans configuration and are linked to increased risk of cardiovascular disease, unlike cis-fatty acids.
C. Trans-fatty acids are saturated, while cis-fatty acids are unsaturated.
D. There is no significant difference between trans- and cis-fatty acids.
27. What is the primary role of hormone-sensitive lipase?
A. Digesting dietary triglycerides in the intestine
B. Hydrolyzing triglycerides stored in adipose tissue
C. Synthesizing triglycerides in the liver
D. Transporting triglycerides in the blood
28. In the context of lipid metabolism, what does `de novo lipogenesis′ refer to?
A. Breakdown of dietary lipids
B. Synthesis of lipids from non-lipid precursors like carbohydrates and proteins
C. Transport of lipids in lipoproteins
D. Oxidation of fatty acids for energy production
29. What are isoprenoids (terpenes) synthesized from?
A. Fatty acids
B. Acetyl-CoA
C. Amino acids
D. Glucose
30. What is the role of lipid droplets in cells?
A. To synthesize proteins
B. To store triglycerides and cholesterol esters
C. To digest cellular waste
D. To generate ATP through oxidative phosphorylation
