Chapter 7 Take Home Test

Singer and Nicolson's fluid mosaic model of the membrane proposed that: a.membranes are a phospholipid bilayer b. membranes are a phospholipid bilayer between two layers of hydrophilic proteins c. membranes are a single layer of phospholipids and proteins d. membranes consist of protein molecules embedded in a fluid bilayer of phospholipids e. membranes consist of a mosaic of polysaccharides and proteins

Which of the following types of molecules are the major structural components of the cell membrane? a. phospholipids and cellulose b. nucleic acids and proteins c. phospholipids and proteins d. proteins and cellulose e. glycoproteins and cholesterol

the presence of cholesterol in the plasma membranes of some animals: a. enables the membrane to stay fluid more easily when cell temperature drops b. enables the animal to remove hydrogen atoms from saturated phospholipids c. enables the animal to add hydrogen atoms to unsaturated phospholipids d. makes the membrane less flexible, allowing it to sustain greater pressure from within the cell e. makes the animal more susceptible to circulatory disorders

according to the fluid mosaic model of cell membranes, which of the following is a true statement about membrane phospholipids? a. they can move laterally along the plane of the membrane 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

In order for a protein to be an integral membrane protein it would have to be: a. hydrophilic b. hydrophobic c. amphipathic, with at least one hydrophobic region d. completely covered with phospholipids e. exposed on only one surface of the membrane

which of the following is true of integral membrane proteins? a. they lack tertiary structure b. they are loosely bound to the surface of the bilayer c. they are usually transmembrane proteins d. they are not mobile within the bilayer e. they serve only a structural role in membranes

the primary function of polysaccharides attached to the glycoproteins and glycolipids of animal cell membranes is: a. to facilitate diffusion of molecules down their concentration gradients b. to actively transport molecules against their concentration gradients c. to maintain the integrity of a fluid mosaic model d. to maintain membrane fluidity at low temperatures e. to mediate cell-to-cell recognition

in the years since the proposal of the fluid mosaic model of the cell membrane, which of the following observations has been added to the model? a. the membrane is only fluid across a very narrow temperature range b. proteins rarely move, even though they possibly can do so c. unsaturated lipids are excluded from the membranes d. the concentration of protein molecules is now known to be much higher e. the proteins are known to be made of only acidic amino acids

A protein that spans the phospholipid bilayer one or more times is: a. a transmembrane protein b. an integral protein c. a peripheral protein d. an integrin e. a glycoprotein

which of these are not embedded in the hydrophobic portion of the lipid bilayer at all? a. transmembrane proteins b. integral proteins c. peripheral proteins d. integrins e. glycoproteins

which of the following is true of the evolution of cell membranes? a. cell membranes have stopped evolving now that they are fluid mosaics b. cell membranes cannot evolve if the membrane proteins do not c. the evolution of cell membranes is driven by the evolution of glycoproteins and glycolipids d. all components of membranes evolve in response to natural selection e. an individual organism selects its preferred type of cell membrane for particular functions

why are the lipids and proteins free to move laterally in membranes? a. the interior of the membrane is filled with liquid water b. lipids and proteins repulse each other in the membrane c. hydrophilic portions of the lipids are in the interior of the membrane d. there are only weak hydrophobic interactions in the interior of the membrane e. molecules such as cellulose can pull them in various directions

what kinds of molecules pass through a cell membrane most easily? a. large and hydrophobic b. small and hydrophobic c. large polar d. ionic e. monosaccharides such as glucose

which of the following is a characteristic feature of a carrier protein in a plasma membrane? a. it is a peripheral membrane protein b. it exhibits a specificity for a particular type of molecule c. it requires the expenditure of cellular energy to function d. it works against diffusion e. it has few, if any, hydrophobic amino acids

nitrous oxide gas molecules diffusing across a cell's plasma membrane is an example of: a. diffusion across the lipid bilayer b. facilitated diffusion c. active transport d. osmosis e. cotransport

which of the following statements is correct about diffusion? a. it is very rapid over long distances b. it requires an expenditure of energy by the cell c. it is a passive process in which molecules move from a region of higher concentration to a region of lower concentration d. it is an active process in which molecules move from a region of lower concentration to one of higher concentration e. it requires integral proteins in the cell membrane

water passes quickly through cell membranes because: a. the bilayer is hydrophilic b. it moves through hydrophobic channels c. water movement is tied to ATP hydrolysis d. it is a small, polar, charged molecule e. it moves through aquaporins in the membrane

Celery stalks that are immersed in fresh water for several hours become stiff and hard. Similar stalks left in a 0.15M salt solution become limp and soft. From this we can deduce that: a. the fresh water and the salt solution are both hypertonic to the cells of the celery stalks b. the fresh water and the salt solution are both hypotonic to the cells of the celery stalks c. the fresh water is hypotonic and the salt solution is hypertonic to the cells of the celery stalks d. the fresh water is hypertonic and the salt solution is hypotonic to the cells of the celery stalks e. the fresh water is isotonic and the salt solution is hypertonic to the cells of the celery stalks

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? a. water will leave the cells, causing them to shrivel and collapse b. NaCl will be exported from the red blood cells by facilitated diffusion c. the blood cells will take up water, swell, and eventually burst d. NaCl will passively diffuse into the red blood cells e. the blood cells will expend ATP for active transport of NaCl into the cytoplasm

which of the following statements correctly describes the normal tonicity conditions for typical plant and animal cells? a. the animal cell is an a hypotonic solution, and the plant cell is in an isotonic solution b. the animal cell is in an isotonic solution, and the plant cell is in a hypertonic solution c. the animal cell is in a hypertonic solution, and the plant cell is in an isotonic solution d. the animal cell is in an isotonic solution, and the plant cell is in a hypotonic solution e. the animal cell is in a hypertonic solution, and the plant cell is in a hypotonic solution