Chapter 5
Which of the following statements correctly describes the normal tonicity relationships between typical plant and animal cells and their respective environments?
Animal cells are generally in an isotonic solution, and plant cells are generally in a hypotonic solution.
In what way do the membranes of a eukaryotic cell vary?
Certain proteins are unique to each kind of membrane.
Osmosis
Diffusion of water through a selectively permeable membrane
active transport
Energy-requiring process that moves material across a cell membrane against a concentration difference(requires transport protein and ATP)
Which of the following is a characteristic feature of a carrier protein in a plasma membrane?
It exhibits a specificity for a particular type of molecule.
Which of the following statements about diffusion is correct?
It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration.
facilitated diffusion
Movement of specific molecules across cell membranes through protein channels
Which of the following would diffuse through the lipid bilayer of a plasma membrane most rapidly?
O2
passive transport
Requires NO energy, Movement of molecules from high to low concentration, Moves with the concentration gradient
fluid mosaic model
Structural model of the plasma membrane where molecules(proteins) are free to move sideways within a lipid bilayer.
How do unsaturated fatty acids help keep any membrane more fluid at lower temperatures?
The double bonds form kinks in the fatty acid tails that prevent adjacent lipids from packing tightly together.
A patient has had a serious accident and lost a lot of blood. In an attempt to replenish body fluids, distilled water — equal to the volume of blood lost — is transferred directly into one of his veins. What will be the most probable result of this transfusion?
The patient's red blood cells will swell because the blood fluid has become hypotonic compared to the cells.
According to the fluid mosaic model of cell membranes, which of the following is a true statement about membrane phospholipids?
They can move laterally along the plane of the membrane.
Mammalian blood contains the equivalent of 0.15 M NaCl. Seawater contains the equivalent of 0.45 M NaCl. What will happen if red blood cells are transferred to seawater?
Water will leave the cells, causing them to shrivel and collapse.
Why are lipids and proteins free to move laterally in membranes?
Weak hydrophobic interactions in the interior of the membrane are easily disrupted.
Which of the following factors would tend to increase membrane fluidity?
a greater proportion of unsaturated phospholipids
The cell membranes of Antarctic ice fish might have which of the following adaptations?
a high percentage of unsaturated fatty acids
selectively permeable
a property of cell membranes that allows some substances to pass through, while others cannot
carrier proteins
bind to molecules and change shape to shuttle them across the membrane
The fluid mosaic model of the membrane proposed that membranes
consist of protein molecules embedded in a fluid bilayer of phospholipids.
The movement of the hydrophobic gas nitrous oxide (N2O) (laughing gas) into a cell is an example of
diffusion through the lipid bilayer
A primary function of cholesterol in the plasma membranes of some animals is to
enable the membrane to stay fluid more easily when the temperature drops.
Which of the following would diffuse through the lipid bilayer of a plasma membrane most slowly, if at all?
glucose
Water passes quickly through cell membranes because
it moves through aquapourin channel proteins
Submerging a red blood cell in distilled water will result in
lysis of the cell
A primary function of polysaccharides attached to glycoproteins and glycolipids of animal cell membranes is to
mediate cell-to-cell recognition
Difussion
movement from an area of higher concentration to an area of lower concentration
Which of the following membrane activities requires energy from ATP hydrolysis?
movement of sodium ions from a lower concentration in a mammalian cell to a higher concentration in the extracellular fluid
The primary structural components of the cell membrane are
phospholipids and proteins
channel proteins
provide corridors that allow a specific molecule or ion to cross the membrane
Submerging a plant cell in distilled water will result in
the cell becoming turgid
Submerging a red blood cell in a hypertonic solution will result in
the cell wall shriveling
Celery stalks that are immersed in fresh water for several hours become turgid (stiff). Celery stalks left in a 0.15 M salt solution become flaccid (limp). From this we can deduce that
the fresh water is hypotonic and the salt solution is hypertonic to the cells of the celery stalks.
