Homework Ch.7

The permeability of a biological membrane to a specific polar solute may depend on which of the following? A. the amount of cholesterol in the membrane B. the types of transport proteins in the membrane C. the phospholipid composition of the membrane D. the presence of unsaturated fatty acids in the membrane E. the types of polysaccharides present in the membrane

What name is given to the process by which water crosses a selectively permeable membrane? A. diffusion B. osmosis C. phagocytosis D. pinocytosis E. passive transport

Which of the following molecules can cross the lipid bilayer of a membrane directly, without a transport protein or other mechanism? Select all that apply. A. carbon dioxide B. water C. lipids D. proteins E. ions F. oxygen G. sucrose

What does only channels do?

What does only carriers do?

What does both channels and carriers do?

Which of the following statements correctly describe(s) the driving forces for diffusion of Na+ and K+ ions through their respective channels? Select all that apply. A. The diffusion of Na+ ions into the cell is facilitated by the Na+ concentration gradient across the plasma membrane. B. The diffusion of Na+ ions into the cell is impeded by the electrical gradient across the plasma membrane. C. The diffusion of K+ ions out of the cell is impeded by the K+ concentration gradient across the plasma membrane. D. The diffusion of K+ ions out of the cell is impeded by the electrical gradient across the plasma membrane. E. The electrochemical gradient is larger for Na+ than for K+.

What's exocytosis?

What's endocytosis?

What does exocytosis and endocytosis have in common?

Which of the following best describes the structure of a biological membrane? A. two layers of phospholipids with proteins either crossing the layers or on the surface of the layers B. two layers of phospholipids (with opposite orientations of the phospholipids in each layer) with each layer covered on the outside with proteins C. a mixture of covalently linked phospholipids and proteins that determines which solutes can cross the membrane and which cannot D. a fluid structure in which phospholipids and proteins move freely between sides of the membrane E. two layers of phospholipids with proteins embedded between the two layers

Which of the following statements about a typical plasma membrane is correct? A. Carbohydrates on the membrane surface are important in determining the overall bilayer structure. B. The two sides of the plasma membrane have different lipid and protein composition. C. The plasma membrane is a covalently linked network of phospholipids and proteins that controls the movement of solutes into and out of a cell. D. The hydrophilic interior of the membrane is composed primarily of the fatty acid tails of the phospholipids. E. Phospholipids are the primary component that determines which solutes can cross the plasma membrane.

When a membrane is freeze-fractured, the bilayer splits down the middle between the two layers of phospholipids. In an electron micrograph of a freeze-fractured membrane, the bumps seen on the fractured surface of the membrane are A. phospholipids. B. cholesterol molecules. C. peripheral proteins. D. integral proteins. E. carbohydrates.

An animal cell lacking oligosaccharides on the external surface of its plasma membrane would likely be impaired in which function? A. attaching the plasma membrane to the cytoskeleton B. maintaining fluidity of the phospholipid bilayer C. cell-cell recognition D. establishing a diffusion barrier to charged molecules E. transporting ions against an electrochemical gradient

A protein that spans the phospholipid bilayer one or more times is A. a peripheral protein. B. an integral protein. C. an integrin. D. a transmembrane protein. E. a glycoprotein

When biological membranes are frozen and then fractured, they tend to break along the middle of the bilayer. The best explanation for this is that A. water that is present in the middle of the bilayer freezes and is easily fractured. B. the hydrophobic interactions that hold the membrane together are weakest at this point. C. the carbon-carbon bonds of the phospholipid tails are easily broken. D. the integral membrane proteins are not strong enough to hold the bilayer together. E. hydrophilic interactions between the opposite membrane surfaces are destroyed on freezing.

The cell membranes of Antarctic ice fish might have which of the following adaptations? A. very long chain fatty acids B. a higher percentage of trans-fatty acids C. a high percentage of polyunsaturated fatty acids D. branched isoprenoid lipids E. no cholesterol

Why are lipids and proteins free to move laterally in membranes? A. Lipids and proteins repulse each other in the membrane. B. Molecules such as cellulose can pull them in various directions. C. There are only weak hydrophobic interactions in the interior of the membrane. D. The interior of the membrane is filled with liquid water. E. Hydrophilic portions of the lipids are in the interior of the membrane.

A phospholipid has a head" made up of glycerol molecule attached to a single ______, which is attached to another small molecule.

Phospholipids vary in the small molecules attached to the phosphate group. The phospholipid shown in the figure has a _________ attached to phosphate.

Because the phosphate group and its attachments are either charged or polar, the phospholipid head is________, which means it has an affinity for water.

A phospholipid also has two "tails" made up of two _________ molecules, which consist of a carboxyl group with a long hydrocarbon chain attached.

Because the C-H bonds in the fatty acit tails are relatively nonpolar, the phsophplipid tails are _________. Which means they are excluded from water.

Extracellular fluid is...?

Cytoplasm is ...?

The membrane protein is..?

Nonpolar molecules(hydrocarbon)

Polar molecules (water)

Ions (Na)

Cystic fibrosis is a genetic disease in humans in which the CFTR protein, which functions as a chloride ion channel, is missing or nonfunctional in cell membranes. The CFTR protein belongs to what category of membrane proteins? A. gap junctions B. electrogenic ion pumps C. aquaporins D. hydrophilic channels E. cotransporters

In facilitated diffusion, what is the role of the transport protein? A. Transport proteins provide a hydrophilic route for the solute to cross the membrane. B. Transport proteins organize the phospholipids to allow the solute to cross the membrane. C. Transport proteins provide the energy for diffusion of the solute. D. Transport proteins provide a low-resistance channel for water molecules to cross the membrane. E. Transport proteins provide a protein site for ATP hydrolysis, which facilitates the movement of a solute across a membrane.

Celery stalks that are immersed in fresh water for several hours become stiff and hard. Similar stalks left in a 0.15 M salt solution become limp and soft. From this we can deduce that A. the fresh water is hypotonic and the salt solution is 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 and the salt solution are both 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. The blood cells will take up water, swell, and eventually burst. B. The blood cells will expend ATP for active transport of NaCl into the cytoplasm. C. NaCl will be exported from the red blood cells by facilitated diffusion. D. NaCl will passively diffuse into the red blood cells. E. Water will leave the cells, causing them to shrivel and collapse.

In which of the following would there be the greatest need for osmoregulation? A. a lymphocyte before it has been taken back into lymph fluid B. a plant being grown hydroponically (in a watery mixture of designated nutrients) C. cells of a tidepool animal such as an anemone D. a red blood cell surrounded by plasma E. an animal connective tissue cell bathed in isotonic body fluid

The movement of glucose into a cell against a concentration gradient is most likely to be accomplished by which of the following? A. passive diffusion of the glucose through the lipid bilayer B. receptor-mediated endocytosis C. facilitated diffusion of the glucose using a carrier protein D. cotransport of the glucose with a proton or sodium ion that was pumped across the membrane using the energy of ATP hydrolysis E. movement of glucose into the cell through a glucose channel

The phosphate transport system in bacteria imports phosphate into the cell even when the concentration of phosphate outside the cell is much lower than the cytoplasmic phosphate concentration. Phosphate import depends on a pH gradient across the membrane-more acidic outside the cell than inside the cell. Phosphate transport is an example of A. active transport. B. osmosis. C. cotransport. D. facilitated diffusion. E. passive diffusion.

The sodium-potassium pump is called an electrogenic pump because it A. is used to drive the transport of other molecules against a concentration gradient. B. contributes to the membrane potential. C. pumps hydrogen ions out of the cell. D. pumps equal quantities of Na+ and K+ across the membrane. E. ionizes sodium and potassium atoms.

Ions diffuse across membranes through specific ion channels A. down the osmotic potential gradients. B. down their concentration gradients. C. down the electrical gradients. D. down their chemical gradients. E. down their electrochemical gradients.

An organism with a cell wall would most likely be unable to take in materials through A. active transport. B. diffusion. C. facilitated diffusion. D. osmosis. E. phagocytosis.

White blood cells engulf bacteria through what process? A. phagocytosis B. osmosis C. pinocytosis D. receptor-mediated exocytosis E. exocytosis

Familial hypercholesterolemia is characterized by which of the following? A. a poorly formed lipid bilayer that cannot incorporate cholesterol into cell membranes B. inhibition of the cholesterol active transport system in red blood cells C. poor attachment of the cholesterol to the extracellular matrix of cells D. a general lack of glycolipids in the blood cell membranes E. defective LDL receptors on the cell membranes

In receptor-mediated endocytosis, receptor molecules initially project to the outside of the cell. Where do they end up after endocytosis? A. on the inside surface of the cell membrane B. on the outside of vesicles C. on the ER D. on the inside surface of the vesicle E. on the outer surface of the nucleus

According to the fluid mosaic model of cell membranes, phospholipids _____. A. frequently flip-flop from one side of the membrane to the other B. have hydrophilic tails in the interior of the membrane C. can move laterally along the plane of the membrane D. occur in an uninterrupted bilayer, with membrane proteins restricted to the surface of the membrane

The membranes of winter wheat are able to remain fluid when it is extremely cold by _____. A. increasing the percentage of unsaturated phospholipids in the membrane B. increasing the percentage of cholesterol molecules in the membrane C. decreasing the number of hydrophobic proteins in the membrane D. cotransport of glucose and hydrogen

An animal cell lacking oligosaccharides on the external surface of its plasma membrane would likely be impaired in which function? A. establishing a diffusion barrier to charged molecules B. attaching the plasma membrane to the cytoskeleton C. transporting ions against an electrochemical gradient D. cell-cell recognition

Which of these are NOT embedded in the hydrophobic portion of the lipid bilayer at all? A. integral proteins B. peripheral proteins C. transmembrane proteins D. All of these are embedded in the hydrophobic portion of the lipid bilayer.

Why are lipids and proteins free to move laterally in membranes? A. Hydrophilic portions of the lipids are in the interior of the membrane. B. The interior of the membrane is filled with liquid water. C. Lipids and proteins repulse each other in the membrane. D. There are only weak hydrophobic interactions in the interior of the membrane

Which of the following most accurately describes selective permeability? A. An input of energy is required for transport. B. Lipid-soluble molecules pass through a membrane. C. There must be a concentration gradient for molecules to pass through a membrane. D. Only certain molecules can cross a cell membrane.

Which of the following would likely move through the lipid bilayer of a plasma membrane most rapidly? A. glucose B. K+ C. an amino acid D. CO2

Which of the following membrane activities requires energy from ATP? A. movement of carbon dioxide out of a paramecium B. movement of Na+ ions from a lower concentration in a mammalian cell to a higher concentration in the extracellular fluid C. movement of glucose molecules into a bacterial cell from a medium containing a higher concentration of glucose than inside the cell D. facilitated diffusion of chloride ions across the membrane through a chloride channel

The sodium-potassium pump is called an electrogenic pump because it _____. A. ionizes sodium and potassium atoms B. pumps equal quantities of Na+ and K+ across the membrane C. is used to drive the transport of other molecules against a concentration gradient D. contributes to the membrane potential

Which of the following correctly describes some aspect of exocytosis or endocytosis? A. Endocytosis and exocytosis involve passive transport. B. The inner surface of a transport vesicle that fuses with or buds from the plasma membrane is most closely related to the inner surface of the plasma membrane. C. Exocytosis and endocytosis change the surface area of the plasma membrane. D. These two processes require the participation of mitochondria. E. Both processes provide a mechanism for exchanging membrane-impermeable molecules between the organelles and the cytosol.

An organism with a cell wall would most likely be unable to take in materials through _____. A. facilitated diffusion B. active transport C. phagocytosis D. osmosis

Which factors affect the rate of osmotic movement of water? A. The rate of osmosis increases with increasing differences in solute concentrations between two solutions separated by a selectively permeable membrane. B. Hydrostatic pressure applied to a hypertonic solution separated from a hypotonic solution by a selectively permeable membrane increases osmotic movement across the membrane. C. No factors have an effect; the rate of osmosis is constant.