This set of Cell Biology Multiple Choice Questions & Answers (MCQs) focuses on “Cellular Membranes – Lipids and Fluidity”.
1. Fluidity and viscosity are the same.
a) True
b) False
View Answer
Explanation: Fluidity and viscosity are not the same and they are inversely related. Fluidity is a measure of ease of flow and viscosity is the resistance to flow.
2. Which of the following attributes of the membrane is most affected at the transition temperature?
a) size
b) fluidity
c) internal composition
d) internal environment
View Answer
Explanation: At the transition temperature, the bilayer distinctly changes from liquid crystalline phase to crystalline gel. This occurs when the temperature is lowered from a standard warm temperature of 37⁰C.
3. The ___________ the degree of unsaturation of the fatty acids of the bilayer, the ___________ the temperature before the bilayer gels.
a) greater, lower
b) greater, more
c) lesser, higher
d) lesser, higher
View Answer
Explanation: When the number of unsaturated fatty acids in the membrane is more, lower the transition temperature at which the membrane gels.
4. Which of the following molecules affects the mobility of fatty acyl chains in the plasma membrane?
a) starch
b) glycogen
c) cholesterol
d) carbohydrates
View Answer
Explanation: Cholesterol disrupts the packing between fatty acyl chains and interferes with their mobility. It makes the membrane durable while decreasing the permeability of the membrane.
5. Which of the following occurs in the membrane, when the temperature is lowered?
a) denaturation
b) desaturation
c) saccharification
d) glycolysis
View Answer
Explanation: When the temperature of the surrounding is lowered, the cells respond metabolically. Membrane remodeling takes place to make the cell more cold resistant. This takes place by desaturation of fatty acyl chains to form double bonds.
6. Lipid rafts are patches of cholesterol and ________________
a) carbohydrates
b) amino acids
c) lipids
d) sphingolipids
View Answer
Explanation: Lipid rafts are the patches of cholesterol and sphingolipids. When membrane lipids are extracted from the membranes to synthesize artificial membranes in vitro, cholesterol and sphingolipids tend to self-assemble.
7. Cell fusion can be performed on two cells from different species.
a) True
b) False
View Answer
Explanation: Cell fusion is a technique to fuse two cells from different species to form one cytoplasm and one single continuous plasma membrane.
8. In the experiments to demonstrate the mobility of membrane proteins, which cells were fused with human cells?
a) mouse cells
b) drosophila cells
c) tumor cells
d) bacterial cells
View Answer
Explanation: The first experiments to demonstrate that membrane proteins can move within the plane of the membrane used fused cells of human and mouse. These were performed in 1970 at the John Hopkins University.
9. Which phenomena are made use of in the technique FRAP?
a) electrostatic
b) photothermal
c) hybridization
d) fluorescence
View Answer
Explanation: Fluorescence recovery after photobleaching (FRAP) is a technique in which integral membrane proteins are labeled with a fluorescent dye, after which they are irradiated by a laser beam.
10. Which type of molecules are used in SPT?
a) organic dye
b) inorganic dye
c) antibodies
d) gold particles
View Answer
Explanation: In the technique of single-particle tracking (SPT), individual membrane proteins are labeled with antibody conjugated gold particles and their movement is traced using computer-enhanced microscopy.
11. The use of optical tweezers in membrane biology was done to confirm the ________________ nature of membranes.
a) self-replicating
b) elastic
c) inelastic
d) photo-responsive
View Answer
Explanation: The integral membrane proteins are tagged with antibody-coated beads that provide for handles that can be gripped by laser beam. The experiments concluded that membrane barriers are elastic in nature.
12. The sperm cell is covered by a _____________
a) sheath
b) cell wall
c) continuous membrane
d) discontinuous membrane
View Answer
Explanation: Of all the cells in mammals, sperms are the most highly differentiated. A mature sperm is divided into three regions head, midpiece and tail; all having their specific functions. The sperm is covered by a continuous plasma membrane that contains a mosaic of specialized domains.
13. Hemolysis is associated with which type of cells?
a) hepatocytes
b) germ cells
c) somatic cells
d) red blood cells
View Answer
Explanation: Hemolysis is the phenomenon when red blood cells are placed in a dilute hypotonic solution which makes the uptake water and resultant swelling. When they swell up, they become leaky and the contents flow out of the cells.
14. Band 3 and glycophorins are membrane proteins that contain ________________
a) carbohydrates
b) sterols
c) lipids
d) nucleic acids
View Answer
Explanation: Band 3 and glycophorins are carbohydrate-containing membrane proteins. Band 3 gets its name from the position in electrophoretic gel; it is present in the membrane as a homodimer.
15. Which is the first membrane protein to have its amino acid sequence determined?
a) Glycophorin A
b) Glycophorin B
c) Glycophorin C
d) Glycophorin D
View Answer
Explanation: Glycophorin A is the first membrane protein to have its amino acid sequence determined. Other glycophorins are present in lesser amount in the membranes. Glycophorin A has carbohydrates attached that account for 60% of its weight.
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