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2.1 Membrane Structure & Composition — Test 1
Q1. Most prokaryotic cells are devoid of:✓ Cholesterol
Q2. Cell membranes are composed mainly of:✓ Lipid and protein
Q3. Membrane fluidity is normally high due to:✓ High proportion of cis-unsaturated fatty acids
Q4. Which statement about biological membranes is NOT true?✓ They contain a symmetrical lipid bilayer
Q5. Which statement best describes passive (simple) diffusion?✓ Rate is proportional to the concentration difference
Q6. Which one of the following membranes would be the MOST fluid?✓ A bilayer of lipids with polyunsaturated 16-carbon fatty acids
Q7. Glycolipids in the plasma membrane are usually located at the:✓ Outer leaflet of the plasma membrane
Q8. All of the following are covered by a lipid monolayer, EXCEPT:✓ Endocytic vesicles
Q9. Smaller ions cannot enter cells through water channels due to:✓ Hydration shells surrounding the ions
Q10. Cold stress-induced increase in membrane fluidity is caused due to:✓ Increase in unsaturated fatty acids
Q11. Fatty acids can be transported into and out of the cell membrane by:✓ Simple diffusion
Q12. In membrane biophysics, which one of the following statements is TRUE?✓ Gouy-Chapman theory describes ion distributions as a function of charges from the membrane surface
Q13. Regions of higher abundance of cholesterol on the plasma membrane will:✓ Be more rigid than the surrounding membrane
Q14. According to the fluid mosaic model, the plasma membrane is composed of:✓ Phospholipids and integral as well as peripheral proteins
Q15. Which of the following holds TRUE for cell membranes of eukaryotic cells?✓ Amphiphilic nature
Q16. In biological membranes, integral proteins and lipids interact mainly by:✓ Hydrophobic interactions
Q17. Which statement is true about membrane fluidity and fatty-acid chain length?✓ The longer the fatty-acid chain, the more the fluidity decreases
Q18. Phosphatidylserine, an important component of the biological membrane, is located in:✓ The inner leaflet but flip-flops to the outer leaflet under specific conditions
Q19. The membrane phospholipids form a bilayer, when water is available on both sides, due to:✓ Its amphipathic nature
Q20. Mark the INCORRECT statement: for most channels in a biological membrane, they typically:✓ Are usually saturable
Q21. Predominant interactions between phospholipids that stabilize a biological membrane include:✓ Hydrophobic interactions and hydrogen bonding
Q22. The primary function of polysaccharides attached to glycoproteins in the animal cell membrane is to:✓ Mediate cell-to-cell recognition
Q23. Which one of the following is energetically favorable and occurs spontaneously in an aqueous solution?✓ Formation of a bilayer from phospholipid molecules
Q24. Glycophorin, having one highly hydrophobic domain, is able to span a phospholipid bilayer membrane only:✓ Once
Q25. Specific solutes move through the membrane much more slowly via transporters than via channels. This is because:✓ Both of the above are correct
Q26. Both sphingomyelin and phosphoglycerides are phospholipids. Which one of the following statements is NOT correct?✓ Only one of them may contain a carbon-carbon double bond (C=C)
Q27. In cell membranes, the lipid molecules are arranged as a continuous double layer with an approximate thickness of:✓ 5 nm
Q28. Membrane-bound and free ribosomes are structurally identical, but at a given time differ only in their association with:✓ Nascent proteins
Q29. In the membrane, transport activities are carried out mainly by __________, while fluidity is maintained mainly by __________.✓ Proteins; lipids
Q30. The cell membrane consists of a phospholipid bilayer with embedded proteins. The polar head in these phospholipids is made up of:✓ A phosphate and an alcohol
Q31. A poikilothermic organism living in the Arctic, compared to one living in a temperate zone, would have a plasma membrane richer in:✓ Unsaturated fatty acids
Q32. Which one of the following is abundant in the plasma membranes of mammalian cells but is absent from most prokaryotic and plant cell membranes?✓ Cholesterol
Q33. Phosphatidylserine (PS) is mostly located in the inner leaflet of the RBC plasma membrane. To prove this using a PS-specific lytic enzyme (PSE) and other reagents, the correct experimental sequence is:✓ RBCs → inside-out vesicles → PSE → Thin-Layer Chromatography (TLC)
Q34. A protein inserts into model liposomes during reconstitution. It has an N-terminal 18-residue hydrophilic segment on the outside, a 19-residue hydrophobic transmembrane segment flanked by negatively and positively charged residues, and a C-terminal domain residing inside the lumen. For proper (correctly oriented) reconstitution, which strategy is appropriate?✓ Increase the positively charged amino acids in the C-terminal
Q35. Two liposome preparations 'X' and 'Y' are made from phosphatidylcholine (PC) and cholesterol. In 'Y', a ganglioside (asialo-GM) is also incorporated ('X' is the negative control). To determine the localization of asialo-GM in the bilayer of 'Y', which reagent(s) are most appropriate?✓ Both B and C
Q36. Which statements are TRUE about membrane-spanning proteins?✓ A, B and C
2.2 Membrane Proteins — Test 2
Q37. Ribophorins are a group of:✓ Transmembrane glycoproteins located in the membrane of RER
Q38. Which statement about ABC (ATP-binding cassette) transporters is correct?✓ They have both a membrane-spanning (substrate-recognizing) domain and an ATP-binding domain
Q39. The distribution of intrinsic (integral) proteins in the cell membrane is:✓ Asymmetrical
Q40. The ability of a membrane protein to span the lipid bilayer strictly depends on the presence of:✓ α helices
Q41. The FRAP (Fluorescence Recovery After Photobleaching) technique confirms which property of the cell membrane?✓ Lateral mobility of membrane proteins
Q42. The 14 highly homologous GLUT glucose-transport proteins encoded by the human genome characteristically contain:✓ 12 membrane-spanning α-helices
Q43. Which of the following is NOT a property of the fluid-mosaic model with respect to bacterial membrane components?✓ Presence of sterols
Q44. Using FRAP, the diffusion coefficients of three integral membrane proteins M1, M2 and M3 in a kidney cell are 1, 0.05 and 0.005 µm²/s respectively. Considering the relationship between an integral protein's structure and its diffusion, which protein(s) would have the HIGHEST number of membrane-spanning domains?✓ M3 only
Q45. Scientists artificially fused mouse cells with monkey cells; the fused cells were labelled with fluorescent antibodies against mouse and monkey surface receptors (X and Y). At 0 min the receptors stayed in their own halves, but after 60 min X and Y had intermixed over the whole surface. Which statement correctly reflects the outcome?✓ The proteins on the membrane surface are in a dynamic state
2.3 Transport Across Membranes — Test 3
Q46. A sodium–potassium pump is a type of:✓ Antiport
Q47. An example of primary active transport is:✓ Na⁺K⁺-ATPase
Q48. The plasma membrane is freely permeable to:✓ Water
Q49. Which one of the following statements is NOT true?✓ Rate of transport by simple diffusion is saturable
Q50. Mark the correct statement about membrane transport:✓ Carrier protein is involved in both active transport and facilitated diffusion
Q51. Which one of the following co-transporters is a symporter?✓ Glucose–Na⁺ co-transporter of intestinal microvilli
Q52. GLUT1 is a well-studied example of a protein that mediates:✓ Facilitated diffusion
Q53. Active transport of a substance across a membrane requires:✓ ATP
Q54. Which one of the following is a P-type ion transporter set?✓ Na⁺, K⁺, Ca²⁺ and H⁺
Q55. Which one of the following is correct for the Na⁺/K⁺-ATPase?✓ Na⁺ and ATP bind on the intracellular side, while K⁺ and ouabain bind on the extracellular side
Q56. Charged molecules like NO₃⁻ will be transported into the cell by:✓ Both transporters and ion channels
Q57. Which statement regarding aquaporins (water channels) is NOT correct?✓ Aquaporins cannot transport uncharged molecules like ammonia
Q58. Which one of the following is a correct statement for the Na⁺/K⁺-ATPase?✓ It gives out 3 Na⁺ and takes in 2 K⁺
Q59. Membrane carrier proteins differ from membrane channel proteins in that:✓ Carrier proteins can mediate active transport, while channel proteins cannot
Q60. Simultaneous movement of two molecules in the same direction is known as:✓ Symport
Q61. Which one of the following is NOT a characteristic feature of aquaporins?✓ They are absent in bacteria
Q62. ATP is used indirectly for which one of the following transport processes?✓ Absorption of glucose from outside to inside via Na⁺-coupled symport
Q63. Which one of the following statements regarding membrane transport is FALSE?✓ Sugars such as glucose are always transported by active transport rather than facilitated diffusion
Q64. Each molecule of the Na⁺/K⁺-ATPase contains the following combination of subunits:✓ 2α and 2β
Q65. In mammalian cells, the Na⁺–sugar and Na⁺–amino acid transporters are an example of:✓ Symport system
Q66. Movement of substances against their concentration gradient in living systems is called:✓ Active transport
Q67. Which represents the correct order of lipid-bilayer permeability, from MOST to LEAST permeable?✓ N₂ > Ethanol > H₂O > Glucose > Ca²⁺ > RNA
Q68. The Na⁺/K⁺-ATPase is predominantly located on which side of the plasma membrane in a polarized epithelial cell?✓ Basolateral
Q69. ATP-driven pumps hydrolyze ATP and use the energy to move ions/solutes. Which statement about these pumps is NOT correct?✓ V-type pumps normally use a voltage gradient to transport small molecules
Q70. Transport of water across aquaporins is regulated by the presence of which sequence of three highly conserved amino acids?✓ Asn-Pro-Ala
Q71. During nerve conduction, the action potential and the Na⁺/K⁺-ATPase pump work in coordination. Which statement is correct?✓ During an action potential Na⁺ moves in and K⁺ moves out, while the Na⁺/K⁺ pump exports Na⁺ and imports K⁺
Q72. Transport of molecules through a cell membrane down a concentration gradient, mediated by a membrane transport protein, is called:✓ Uniporter
Q73. The superfamily of membrane transporters that actively transports a variety of small molecules such as sugars, peptides and amino acids is the:✓ ABC transporters
Q74. The Na⁺/K⁺-ATPase pump is found on the plasma membrane of most animal cells. A mutation in the intrinsic phosphorylation site of the pump is most likely to affect:✓ Both the inward and outward movement of K⁺ and Na⁺
Q75. The Na⁺ concentration outside a cell is 100 mM and inside is 10 mM; lactose is 10 mM on both sides. With an integral membrane protein that symports Na⁺ and lactose, which result do you expect?✓ Both lactose and Na⁺ will enter the cell
Q76. A process in which the movement of one molecule across the membrane down its concentration gradient is coupled to the movement of a second molecule up its gradient in the opposite direction is called:✓ Antiport
Q77. Glycophorin spans the RBC membrane once, with its N-terminus extracellular and its C-terminus on the cytosolic side. Using fluorophore-labelled antibodies against the N- and C-terminal peptides, which statement is correct?✓ Permeabilized RBCs can be labelled with both C-terminal and N-terminal antibodies
Q78. Which of the following statements are correct about transport ATPases?✓ A, B, C and D
2.4 Bulk Transport — Test 4
Q79. Pinocytosis is a form of:✓ Bulk transport
Q80. Select the INCORRECT statement:✓ Phagocytosis is a form of exocytosis
Q81. The word 'phagocytosis' refers to:✓ Cell eating
Q82. The process by which a cell secretes macromolecules by fusing a vacuole/vesicle membrane to the plasma membrane is called:✓ Exocytosis
Q83. In polarized cells (e.g., epithelial cells), an internalized receptor is moved across the cell to the opposite domain of the plasma membrane. This process is called:✓ Transcytosis
Q84. Which transport processes are carried out by receptor-mediated endocytosis?✓ 1 and 3
Q85. Choose the correct sequence to fill the blanks: (1) the general process by which fluids/particles are transported into cells; (2) the specific term for engulfing fluid; (3) the specific term for engulfing particles; (4) substances taken in within membrane-enclosed sacs.✓ 1-Endocytosis; 2-pinocytosis; 3-phagocytosis; 4-vesicles
2.5 Membrane Potential & Cellular pH — Test 5
Q86. The purpose of Na⁺ ions in the coupled transport of solutes is to:✓ Enforce spontaneity of the process
Q87. Hemolysis of red blood cells takes place when they are suspended in which one of the following solutions?✓ 0.5% NaCl
Q88. When an animal cell is placed in 0.5 M sucrose solution, its volume does not change. When the same cell is transferred to 0.5 M NaCl solution, its volume will:✓ Decrease
Q89. You must identify the source of two cultures of a single-celled organism, A and B — one from a turbid river, the other from a clean pond. Which experiment will give the answer?✓ Culture both in distilled water; the one that bursts is from the river