Chapter 6: Lipids, Membranes, and the First Cells. Flashcards
The three types of lipids found in cells (fats, steroids, and phospholipids) are insoluble in water because they all possess _____.
A) a significant component of hydrocarbons
B) a multiring structure
C) many ester linkages between components
D) fatty acids
A) a significant component of hydrocarbons
What type of chemical interactions do phospholipids have with their environments?
A) hydrophilic
B) hydrophobic
C) amphipathic
D) covalent
C) amphipathic
What happens when phospholipids are poured into water?
A) They incorporate proteins into their interior.
B) They form liposomes.
C) They are solubilized in water because of their polar phosphate groups.
D) The phosphate groups dissociate from the phospholipids, and the remaining part (the lipid) clumps together.
B) They form liposomes.
Which type of molecule moves across a cell membrane most easily?
A) lipid-soluble, nonpolar molecules such as oxygen and carbon dioxide
B) ions such as chloride
C) large polar molecules, such as glucose
D) uncharged, polar amino acids
A) lipid-soluble, nonpolar molecules such as oxygen and carbon dioxide
Which of the following would decrease membrane fluidity?
A) an increase in the number of transmembrane proteins
B) an increase in the number of C—C double bonds of fatty acids in the membrane
C) a shorter chain length of fatty acids
D) increased level of saturation of fatty acids
D) increased level of saturation of fatty acids
_____ are artificial membrane-bound vesicles.
A) Phospholipids
B) Steroids
C) Liposomes
D) Lipids
C) Liposomes
The degree of saturation of phospholipids in a membrane will affect which of the following functions of phospholipids?
A) the ability of phospholipids to form phosphodiester bonds with other phospholipids
B) the formation of liposomes
C) the permeability of the membrane
D) the ability of the phosphate group to bind to a small-molecular-weight hydrophilic molecule
C) the permeability of the membrane
Simple diffusion is most accurately described by which of the following?
A) Simple diffusion is an energy-requiring process.
B) The process of simple diffusion is independent of temperature and the distance a molecule diffuses.
C) Solutes are transported across a cell membrane by a carrier in a direction independent of solute concentration.
D) Solutes must be soluble in the cell membrane, and a concentration gradient must be present in order for any net diffusion to take place.
D) Solutes must be soluble in the cell membrane, and a concentration gradient must be present in order for any net diffusion to take place.
Region A has a low solute concentration. Region B has a high solute concentration. They are separated by a selectively permeable membrane. The movement of water from region A to region B occurs by the process of _____.
A) osmosis
B) active transport
C) equilibrium
D) facilitated diffusion
A) osmosis
Which of the following contributes to osmotic pressure?
A) solute concentration
B) equilibrium
C) phospholipid molecules present in the cell membrane
D) gravity
A) solute concentration
A red blood cell that is placed in distilled water will _____
A) gain water and expand
B) lose glucose and solutes to the distilled water
C) remain unchanged
D) lose water and shrink
A) gain water and expand
Which one of the following statements is true of cell membranes?
A) They are permeable to all organic compounds.
B) Phospholipids are constantly in motion and often flip from one side of the bilayer to the other (that is, go from facing the cytoplasm to facing the external environment).
C) Amphipathic proteins can span the membrane.
D) The part of the membrane facing the external environment is identical to the membrane layer facing the cytoplasm.
C) Amphipathic proteins can span the membrane.
Proteins are amphipathic molecules that contain nonpolar (hydrophobic) amino acids and polar (hydrophilic) amino acids. Where would you expect to find the hydrophobic and hydrophilic amino acid residues of a protein that spans a cell membrane?
A) Membrane proteins are oriented such that their amino acid residues do not come into contact with the membrane interior.
B) The hydrophobic amino acids would be oriented toward the outside of the protein and come into contact with the hydrocarbon tails of the phospholipid bilayer, whereas the hydrophilic proteins would be more concentrated in the protein interior.
C) The hydrophobic regions of the protein would clump together in the protein interior through hydrophobic interactions, whereas the hydrophilic regions would be oriented outward, coming into contact with the phospholipid bilayer.
D) Proteins are found only on the membrane surface. The hydrophilic regions would be attached to the phosphate groups of membrane phospholipids through ionic bonds, whereas the hydrophobic groups would be oriented toward the extracellular fluid.
B) The hydrophobic amino acids would be oriented toward the outside of the protein and come into contact with the hydrocarbon tails of the phospholipid bilayer, whereas the hydrophilic proteins would be more concentrated in the protein interior.
Which of the following statements best describes results of an experiment designed to test whether the protein cystic fibrosis transmembrane conductance regulator (CFTR) is a chloride channel?
A) Electric current flowed only in the presence of CFTR, but researchers could not distinguish which ions were present.
B) The presence of CFTR altered the solubility of chlorine ions in the plasma membrane.
C) Electric current flowed only in the presence of CFTR, indicating the movement of chloride ions.
D) The presence of CFTR caused chloride ions to increase both inside and outside of the cell membranes.
C) Electric current flowed only in the presence of CFTR, indicating the movement of chloride ions.
The transmembrane transport protein GLUT-1 transports _____.
A) all sugars
B) glucose and other six-carbon sugars
C) glucose
D) ribose
C) glucose
