COPY OF MOLECULES TO CELLS - Unit 2 TEST QUESTIONS AND CORRECT ANSWERS

COPY OF MOLECULES TO CELLS - Unit 2 TEST QUESTIONS AND CORRECT ANSWERS 1. Which of the following statement is correct about membrane cholesterol? (A) The hydroxyl group is located near the centre of the lipid layer (B) Most of the cholesterol is in the form of a cholesterol ester (C) The steroid nucleus form forms a rigid, planar structure (D) The hydrocarbon chain of cholesterol projects into the extracellular fluid 2. Which of the following phospholipids is localized to a greater extent in the outer leaflet of the membrane lipid bilayer? (A) Choline phosphoglycerides (B) Ethanolamine phosphoglycerides (C) Inositol phosphoglycerides (D) Serine phosphoglycerides 3. Fluidity of membranes is increased by the following constituent except (A) Polyunsaturated fatty acids (B) Saturated fatty acids (C) Integral proteins (D) Cholesterol 4. Transition temperature of membranes may be affected by the following constituent of membranes: (A) Peripheral proteins (B) Integral proteins (C) Cholesterol (D) Oligosachharides 5. Phospholipid acting as surfactant is (A) Cephalin (B) Phosphatidyl inositol (C) Lecithin (D) Phosphatidyl serine 6. Which of the following is a characteristic of the plasma membrane? (A) It is composed principally of triacylglycerols and cholesterol (B) It contains principally nonpolar lipids. (C) It contains phospholipids with their acyl groups extending into the cytosol. (D) It contains more phosphatidylserine in the inner than the outer leaflet. (E) It contains oligosaccharides sandwiched between the inner and outer leaflets. 7. Carrier proteins can (A) Transport only one substance (B) Transport more than one substance (C) Exchange one substance to another (D) Perform all of these functions 8. A lipid bilayer is permeable to (A) Urea (B) Fructose (C) Glucose (D) Potassium 9. Liposomes: (A) Are lipid bilayered (B) Have water in the middle (C) Are carriers of drugs (D) All of these 10. Tay-Sachs disease results from inherited deficiency of (A) Arylsulphatase A (B) Hexosaminidase A (C) Sphingomyelinase (D) Ceramidase 11. A message transmitted by which example of a chemical messenger would most likely be negatively affected by a mutation that greatly reduced the fluidity of the plasma membrane? (A) Cytokine (B) Steroid hormone (C) A transforming growth factor (D) Insulin (E) Glucagon 12. A premature infant, when born, had low Apgar scores and was having difficulty breathing. The NICU physician injected a small amount of a lipid mixture into the child’s lungs, which greatly reduced the respiratory distress the child was experiencing. In addition to proteins, a key component of the mixture was which one of the following? (A) Sphingomyelin (B) A mixture of gangliosides (C) Triacylglycerol (D) Phosphatidylcholine (E) Prostaglandins E and F 13. Bacteria grown at 15°C contain a different fatty acid composition in their membranes as compared to bacteria grown at 37°C. Which one of the following would best represent the composition of the fatty acids at these two different temperatures? (A) Bacteria at the lower temperature would contain a higher percentage of saturated fatty acids than bacteria grown at the higher temperature. (B) Bacteria grown at the lower temperature would have a higher percentage of long-chain fatty acids than bacteria grown at the higher temperature. (C) Bacteria grown at the lower temperature would have a higher percentage of unsaturated fatty acids than bacteria grown at the higher temperature. (D) Bacteria grown at the lower temperature would have an increased level of cholesterol as compared to bacteria grown at the higher temperature. (E) Bacteria grown at the lower temperature would have a decreased level of cholesterol as compared to bacteria grown at the higher temperature. 14. A patient presents with rapidly progressive weakness of the lower extremities, loss of deep tendon reflexes, respiratory distress, and autonomic dysfunction following a flu like illness. This disease is an autoimmune inflammatory reaction to tissue made up chiefly of which of the following chemical structures? (A) High-density lipoproteins (B) Elastin (C) Sphingolipids (D) Glycoproteins (E) Glycogen 15. A newborn infant had trouble breathing at birth. The infant was 3 months premature. The physicians treated the infant with a solution, which was directly injected into the lungs. Within seconds, the infant responded with much improved breathing. A major component of this solution is which one of the following? (A) Dipalmitoyl phosphatidylcholine (B) Palmitate containing ceramide (C) Sphingosine (D) Sphingomyelin (E) Diacylglycerol 16. Considering the case in the previous question, the major function of the suspension utilized to improve breathing is which of the following? (A) To allow oxygen exchange with red blood cells (B) To facilitate carbon dioxide extraction from red blood cells (C) To reduce surface tension at the air–water interface (D) To stabilize the structure of lung cells (E) To facilitate blood flow through the lung 17. Your patient has a mechanical heart valve and is chronically anemic due to damage to red blood cells as they pass through this valve. One of the signals that target damaged red blood cells for removal from the circulation is the presence of phosphatidylserine in the outer leaflet of the red cell membrane. Phosphatidylserine is an integral part of cell membranes and is normally found in the inner leaflet of the red cell membrane. This flip-flop of phosphatidylserine between membrane leaflets exposes which part of the phosphatidylserine to the environment? (A) The head group (B) Fatty acids (C) Sphingosine (D) Glycerol (E) Ceramide 18. When fatty acids are added to water, they aggregate to form micelles. Which ONE of the following is the most important driving force for aggregation? (A) Hydrogen bonding between the adjacent carboxy groups. (B) Reduction of the hydrocarbon surface area exposed to water. (C) Van der Waals interactions between carboxyl groups and water. (D) Electrostatic interactions between the carboxyl groups and water. (E) Hydrogen bond formation between fatty acids in the micelle. 19. Which of the following is NOT a characteristic of an animal plasma membrane? (A) provides mechanical strength (B) provides mechanical shape (C) responsible for the synthesis of ATP (D) maintains cellular homeostasis (E) regulates passage of molecules into and out of the cell 20. Which of the following describes the fluid-mosaic model of the plasma membrane structure? (A) phospholipid monolayer with embedded proteins (B) phospholipid bilayer with embedded proteins (C) phospholipid trilayer with embedded proteins (D) triglyceride bilayer with embedded proteins (E) triglyceride monolayer with embedded proteins 21. Which of the following statements is NOT correct regarding the plasma membrane structure? (A) Protein molecules may be partially or wholly embedded. (B) Protein molecules are localized toward one side of the cell. (C) Phospholipids form a bilayer. (D) Phospholipids have a fluid consistency. (E) The head of the phospholipid molecule is attracted toward water. 22. Which of the following statements is NOT correct about the phospholipid molecules in the plasma membrane? (A) Each phospholipid molecule has four nonpolar tails. (B) Each phospholipid molecule has one polar head. (C) The phospholipid heads are attracted to water. (D) The phospholipid tails are not attracted to water. (E) The phospholipid heads face outward 23. Which molecule in animal plasma membranes reduces the permeability of the membrane to most biological molecules? (A) Proteins (B) Phospholipids CONTINUED...DOWNLOAD FOR BEST SCORES