Quiz 3 - Cell Membranes
According to the fluid-mosaic model of cell membranes, which of the following is a TRUE statement about membrane phospholipids? A) they move laterally along the plane of the membrane in 2 dimensions B) they frequently flip-flop from one side of the membrane to the other C) they occur in an uninterrupted bilayer, with membrane proteins restricted to the surface of the membrane D) they are free to depart from the membrane and dissolve in the surrounding solution E) they have hydrophilic tails in the interior of the membrane
A
The relative molar concentrations of potassium inside the cells of a certain red algae growing in sea water is much higher than in the surrounding water. In order to do this, the cells must use: A) low cellular concentrations of sodium B) high cellular concentrations of potassium C) ATP as an energy source D) glucose for binding and releasing ions E) plant hormones embedded in the cell membrane
A
What chemical property characterizes the interior of phospholipid bilayer? A) It is hydrophobic B) It is hydrophilic C) It is polar D) It is saturated E) None of the above
A
Which of the following would move through the lipid bilayer of a plasma membrane most rapidly? A) CO2 B) an amino acid C) glucose D) K+ E) starch
A
Which region(s) of the phospholipid are hydrophilic "water-loving"? A) the phosphate group B) the hydrocarbon chain C) the hydrogen bonds D) neither E) all
A
A bacterium is suddenly expelled from a warm human intestine into the cold world outside. Which of the following adjustments might the bacterium make to maintain the same level of membrane fluidity? A) Produce lipids with hydrocarbon tails that are longer and have fewer double bonds. B) Produce lipids with hydrocarbon tails that are shorter and have more double bonds. C) Decrease the amount of cholesterol in the membrane. Decrease the amount of glycolipids in the membrane.
B
The principal intracellular cations in the cytosol are A) sodium ions B) chloride ions C) potassium ions D) calcium ions E) molybden ions
C
Which of the following statements about the carbohydrate coating of the cell surface is FALSE? A) It is not usually found on the cytosolic side of the membrane B) It can play a role in cell-cell adhesion. C) The arrangement of the oligosaccharide side chains is highly ordered, much like the peptide bonds of a polypeptide chain. D) Specific oligosaccharides can be involved in cell-cell recognition.
C
Potato cells placed in distilled water will: A) lose water and become flaccid B) transport water out of the cell by active transport C) take up water and burst D) take up water and become turgid E) take up water by pinocytosis
D
The transmembrane domain of an integral membrane protein: A) Is composed of hydrophobic amino acids B) Often forms an alpha-helical structure C) Can cross the membrane multiple times D) Is all of the above E) There are no transmemebrane proteins
D
Which of the following determines whether or not a substance will diffuse across a cell membrane? A) Whether the substance is polar or nonpolar B) Whether the substance is large or small C) Whether there is a concentration difference on either side of the membrane D) All of the above E) None of the above
D
Which of the following membrane lipids does not contain a fatty acid tail? A) Phosphatidylcholine B) Glycolipid C) Phosphatidylserine D) Cholesterol
D
Which of the following statements is TRUE? Amoebae (single celled animals) have transporter proteins that actively pump water molecules from the cytoplasm to the cell exterior B) Bacteria and animal cells rely on the Na+-K+ pump in the plasma membrane to prevent lysis resulting from osmotic imbalances C) The Na+-K+ pump allows animal cells to thrive under conditions of very low ionic strength. D) The Na+-K+ pump helps to keep both Na+ and Cl- ions out of the cell.
D
The spontaneous formation of a lipid bilayer in an aqueous environment occurs because: A) The polar head groups of the phospholipids can interact with water B) The long fatty acid tails of the phospholipids can interact with water C) The fatty acid tails of the phospholipids are hydrophobic D) Both A and C E) All of the above
E
Which of the following is true about phospholipids? A) They are completely hydrophobic (i.e., "water-avoiding") B) They have both hydrophobic (i.e., "water-avoiding") and hydrophilic (i.e., "water-loving") regions C) Their phosphate head groups favorably interact with water D) They self-assemble into a bilayer in the presence of water to shield their hydrophobic hydrocarbon tails from having to interact with water molecules E) Answers B-D are correct
E
Which of the following is true about the cellular plasma membrane? A) It is composed of phospholipids and proteins B) It allows dynamic exchange between the inside of the cell and the outside environment. C) It is a fundamental part of every living cell. D) It exists only in bacteria. E) Answers A-C are correct
E
Active transport across membranes does not require energy from hydrolysis of ATP True False
F
Peptide bonds are polar and thus must be covalently modified before proteins can be inserted into the membrane True False
F
Plasma membrane has a minor role in functions of the cell and is not really necessary True False
F
Passive transport across membranes does not require energy from hydrolysis of ATP True False
T
Plasma membrane is highly selective and allows only certain molecules to pass though True False
T
The specific function of a membrane within a cell is determined by the: A) Degree of saturation of fatty acids within the phospholipid bilayer B) Location of membrane within the cell C) Presence of lipid rafts and cholesterol D) Type and number of membrane proteins E) All membranes have the same set of functions in all cells
d
