Upgrade to remove ads
Biology Chapter 7
Terms in this set (84)
membrane defines and limits the cell
Controls entrance and exit from the cell
Selective permeability - allows certain substances in while excluding others
fluid mosaics of lipids and proteins
Membranes are predominantly phospholipids
Both membrane phospholipids and proteins are amphipathic (the molecules have both hydrophilic and hydrophobic regions on the same molecule)
Carbohydrates are usually limited to the outer membrane
fluid mosaic model
a fluid matrix of phospholipids with a mosaic of proteins embedded in it
Sandwich model - supported originally by electron microscopy but had problems explaining permeability
False assumption that all membranes were identical
Fluid mosaic model was found to be consistent with the known physiological characteristics of living membranes
fluidity of membranes
Membranes are held together by hydrophobic interactions. Molecules float about in the membrane. Membrane molecules are in constant rapid motion. Some proteins are structurally controlled in their mobility. Some cannot move at all. They are controlled by the cytoskeleton. Membranes with unsaturated hydrocarbons resist cooling more than those with saturated hydrocarbons. Cholesterol helps stabilize membranes by impeding the movement of phospholipids. It is called a "temperature buffer". Solidification of a membrane usually inactivates its proteins
More than 50 different proteins associated with the red blood cell membrane (one of the simpler cells of the human body)
Cell function is dependent on the proteins
membrane protein functions
b. Enzymic activity
c. Signal transduction
d. Cell - cell recognition
e. Intracellular adhesion
f. Attachment to cytoskeleton and the extracellular matrix
have a hydrophobic part and are transmembranal
are not embedded in the membrane but are on the inner or outer surface. They are usually bound to integral proteins and are usually associated with the cytoskeleton on the inner surface and the extracellular matrix on the outer surface
cell-cell recognition vital in
a. Embryological development
b. Immune recognition - self from non-self
c. Glycolipids - lipid-carbohydrate complexes
d. Glycoproteins - protein-carbohydrate complexes
e. Human blood groups are good examples of this
synthesis and sidedness of membranes
They have distinct inside and outside faces
The lipid bilayer may be composed of different lipids
Integral proteins are specifically oriented for inside and outside
They are made thusly in the ER
Vesicle fusion with plasma membrane is consistent with this orientation of lipids and proteins
Nutrients are allowed in selectively
Metabolic waste is removed selectively
O2, CO2, Na+, K+, Ca2+ and Cl- are selectively regulated
membrane selectively permeable
1. Hydrophobic molecules like CO2 and O2 cross the membrane relatively quickly
2. Hydrophilic molecules cross slowly, if at all, and usually require some form of aid
specific for what they transport
Span the membrane. Channel proteins - facilitate passage of certain molecules and ions. Aquaporins - water specific channel proteins. Carrier proteins - bond to specific molecules and change shape to take the molecule in or out. Glucose transporter will not bind to fructose
the tendency of molecules of a given substance to spread out evenly in a certain space
diffusion from an area of higher concentration to an area of lower concentration
when as many molecules of a substance are diffusing one way as the other
O2 diffuses into a cell and will continue to do so as long as it is being changed to something else by metabolism
diffusion across a membrane without the expenditure of energy
diffusion of water across a membrane
ability of a solution to cause a cell to gain or lose water
solution with the same concentration as the cell
solution that is more concentrated than the cell so that the cell loses water to the solution. Cell can shrink (become crenated). Drinking seawater can do this to a person
solution is less concentrated than the cell so that the cell gains water. Can lead to cytolysis
ability of a cell to control the amount of water it allows in or out
a cell with enough water to push against the cell wall
when a cell is in an isotonic solution and water does not push against the cell wall
A cell placed in a hypertonic solution will lose water and become wilted.
Transmembranal passage aided by transport proteins. It does not require energy and is very specific for the substance transported. Ion channels or gated channels - stimulated to open or close by chemical or electrical stimuli
Movement of a substance against their gradient
Requires energy in the form of ATP
Cell have electrical voltage across the membrane. Voltage is electrical potential energy or a separation of opposite charges. Cytoplasm is more electronegative than the extracellular fluid. Membrane potential may range from -50 to -200 millivolts (mV). Passage of cations into the cell is favored because of the electronegativity of the cytoplasm and anions are favored leaving the cell
two forces act on ion passage - chemical and electrical
a transport protein that generates voltage across a membrane
pumps H+ out of a cell
a transported substance may facilitate the transport of another substance
Example of a proton pump facilitating sucrose transport
secretion of macromolecules by membrane bound vesicles
ingestion of macromolecules by forming membrane bound vesicles
1. Phagocytosis - cell eating
2. Pinocytosis - cell drinking
3. Receptor mediated endocytosis
1) For a protein to be an integral membrane protein, it would have to be _____.
C) amphipathic, with at least one hydrophobic region
D) exposed on only one surface of the membrane
2) You have a planar bilayer with equal amounts of saturated and unsaturated phospholipids. After testing the permeability of this membrane to glucose, you increase the proportion of unsaturated phospholipids in the bilayer. What will happen to the membrane's permeability to glucose?
A) Permeability to glucose will increase.
B) Permeability to glucose will decrease.
C) Permeability to glucose will stay the same.
D) You cannot predict the outcome. You simply have to make the measurement. Answer: A
3) According to the fluid mosaic model of cell membranes, phospholipids _____.
A) can move laterally along the plane of the membrane
B) frequently flip-flop from one side of the membrane to the other
C) occur in an uninterrupted bilayer, with membrane proteins restricted to the surface of the membrane
D) have hydrophilic tails in the interior of the membrane
4) 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 Answer: A
5) Some regions of the plasma membrane, called lipid rafts, have a higher concentration of cholesterol molecules. At higher temperatures, these regions _____.
A) are more fluid than the surrounding membrane
B) are less fluid than the surrounding membrane
C) detach from the plasma membrane and clog arteries
D) have higher rates of lateral diffusion of lipids and proteins into and out of these regions
6) Singer and Nicolson's fluid mosaic model of the membrane proposed that membranes_____.
A) are a phospholipid bilayer between two layers of hydrophilic proteins
B) are a single layer of phospholipids and proteins
C) consist of protein molecules embedded in a fluid bilayer of phospholipids
D) consist of a mosaic of polysaccharides and proteins
7) An animal cell lacking oligosaccharides on the external surface of its plasma membrane would likely be impaired in which function?
A) transporting ions against an electrochemical gradient
B) cell-cell recognition
C) attaching the plasma membrane to the cytoskeleton D) establishing a diffusion barrier to charged molecules
8) 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) All of these are embedded in the hydrophobic portion of the lipid bilayer. Answer: C
9) Why are 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. Answer: D
5) Cell membranes are asymmetrical. Which of the following statements is the most likely explanation for the membrane's asymmetrical nature?
A) Since the cell membrane forms a border between one cell and another in tightly packed tissues such as epithelium, the membrane must be asymmetrical
B) Since cell membranes communicate signals from one organism to another, the cell membranes must be asymmetrical.
C) The two sides of a cell membrane face different environments and carry out different functions.
D) Proteins only function on the cytoplasmic side of the cell membrane, which results in the membrane's asymmetrical nature.
16) In what way do the membranes of a eukaryotic cell vary?
A) Phospholipids are found only in certain membranes.
B) Certain proteins are unique to each membrane.
C) Only certain membranes of the cell are selectively permeable.
D) Some membranes have hydrophobic surfaces exposed to the cytoplasm, while others have hydrophilic surfaces facing the cytoplasm.
17) Which of the following is a reasonable explanation for why unsaturated fatty acids help keep a membrane more fluid at lower temperatures?
A) The double bonds form kinks in the fatty acid tails, preventing adjacent lipids from packing tightly.
B) Unsaturated fatty acids have a higher cholesterol content and, therefore, more cholesterol in membranes.
C) Unsaturated fatty acids are more polar than saturated fatty acids.
D) The double bonds block interaction among the hydrophilic head groups of the lipids.
18) What kinds of molecules pass through a cell membrane most easily?
A) large and hydrophobic
B) small and hydrophobic
C) large polar
19) 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.
20) Which of the following is a characteristic feature of a carrier protein in a plasma membrane?
A) It exhibits a specificity for a particular type of molecule.
B) It requires the expenditure of cellular energy to function.
C) It works against diffusion.
D) It has no hydrophobic regions.
21) Which of the following would likely move through the lipid bilayer of a plasma membrane most rapidly?
B) an amino acid
22) Which of the following allows water to move much faster across cell membranes?
A) the sodium-potassium pump
C) peripheral proteins
23) You are working on a team that is designing a new drug. For this drug to work, it must enter the cytoplasm of specific target cells. Which of the following would be a factor that determines whether the molecule selectively enters the target cells?
A) hydrophobicity of the drug molecule
B) lack of charge on the drug molecule
C) similarity of the drug molecule to other molecules transported by the target cells
D) lipid composition of the target cells' plasma membrane
24) Diffusion _____.
A) is very rapid over long distances
B) requires an expenditure of energy by the cell
C) is a passive process in which molecules move from a region of higher concentration to a region of lower concentration
D) requires integral proteins in the cell membrane
25) Which of the following processes includes all others?
B) facilitated diffusion
C) passive transport
D) transport of an ion down its electrochemical gradient
26) When a cell is in equilibrium with its environment, which of the following occurs for substances that can diffuse through the cell?
A) There is random movement of substances into and out of the cell.
B) There is directed movement of substances into and out of the cell.
C) There is no movement of substances into and out of the cell. D) All movement of molecules is directed by active transport. Answer: A
27) Which of the following is true of osmosis?
A) Osmosis only takes place in red blood cells.
B) Osmosis is an energy-demanding or "active" process.
C) In osmosis, water moves across a membrane from areas of lower solute concentration to areas of higher solute concentration.
D) In osmosis, solutes move across a membrane from areas of lower water concentration to areas of higher water concentration.
30) A patient was involved a serious accident and lost a large quantity of blood. In an attempt to replenish body fluids, distilled water—equal to the volume of blood lost—is added to the blood directly via one of his veins. What will be the most probable result of this transfusion?
A) The patient's red blood cells will shrivel up because the blood has become hypotonic compared to the cells.
B) The patient's red blood cells will swell and possibly burst because the blood has become hypotonic compared to the cells.
C) The patient's red blood cells will shrivel up because the blood has become hypertonic compared to the cells.
D) The patient's red blood cells will burst because the blood has become hypertonic compared to the cells.
36) Celery stalks that are immersed in fresh water for several hours become stiff. Similar stalks left in a 0.15 M salt solution become limp. From this we can deduce that the fresh water_____.
A) and the salt solution are both hypertonic to the cells of the celery stalks
B) is hypotonic and the salt solution is hypertonic to the cells of the celery stalks
C) is hypertonic and the salt solution is hypotonic to the cells of the celery stalks D) is isotonic and the salt solution is hypertonic to the cells of the celery stalks
37) What will happen to a red blood cell (RBC), which has an internal ion concentration of about 0.9 percent, if it is placed into a beaker of pure water?
A) The cell would shrink because the water in the beaker is hypotonic relative to the cytoplasm of the RBC.
B) The cell would shrink because the water in the beaker is hypertonic relative to the cytoplasm of the RBC.
C) The cell would swell because the water in the beaker is hypotonic relative to the cytoplasm of the RBC.
D) The cell will remain the same size because the solution outside the cell is isotonic. Answer: C
38) Which of the following statements correctly describes the normal tonicity conditions for typical plant and animal cells? The animal cell is in _____.
A) a hypotonic solution, and the plant cell is in an isotonic solution
B) an isotonic solution, and the plant cell is in a hypertonic solution
C) a hypertonic solution, and the plant cell is in an isotonic solution
D) an isotonic solution, and the plant cell is in a hypotonic solution Answer: D
39) In which of the following would there be the greatest need for osmoregulation?
A) an animal connective tissue cell bathed in isotonic body fluid
B) a salmon moving from a river into an ocean
C) a red blood cell surrounded by plasma
D) a plant being grown hydroponically in a watery mixture of designated nutrients Answer: B
40) When a plant cell, such as one from a rose stem, is submerged in a very hypotonic solution, what is likely to occur?
A) The cell will burst.
B) Plasmolysis will shrink the interior.
C) The cell will become flaccid.
D) The cell will become turgid.
41) A sodium-potassium pump _____.
A) moves three potassium ions out of a cell and two sodium ions into a cell while producing an ATP for each cycle
B) move three sodium ions out of a cell and two potassium ions into a cell while consuming an ATP for each cycle
C) moves three potassium ions out of a cell and two sodium ions into a cell while consuming 2 ATP in each cycle
D) move three sodium ions out of a cell and two potassium ions into a cell and generates an ATP in each cycle
42) The sodium-potassium pump is called an electrogenic pump because it _____.
A) pumps equal quantities of Na+ and K+ across the membrane
B) contributes to the membrane potential
C) ionizes sodium and potassium atoms
D) is used to drive the transport of other molecules against a concentration gradient Answer: B
43) Which of the following membrane activities requires energy from ATP?
A) facilitated diffusion of chloride ions across the membrane through a chloride channel
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) movement of carbon dioxide out of a paramecium
44) The voltage across a membrane is called the _____.
A) chemical gradient
B) membrane potential
C) osmotic potential
D) electrochemical gradient
45) Ions diffuse across membranes through specific ion channels down _____.
A) their chemical gradients
B) their concentration gradients
C) the electrical gradients
D) their electrochemical gradients
46) Which of the following would increase the electrochemical gradient across a membrane?
A) a sucrose-proton cotransporter
B) a proton pump
C) a potassium channel
D) both a proton pump and a potassium channel
47) 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) passive diffusion
B) facilitated diffusion
C) active transport
48) In some cells, there are many ion electrochemical gradients across the plasma membrane even though there are usually only one or two proton pumps present in the membrane. The gradients of the other ions are most likely accounted for by _____.
A) cotransport proteins
B) ion channels
C) pores in the plasma membrane
D) passive diffusion across the plasma membrane
49) Which of the following is most likely true of a protein that cotransports glucose and sodium ions into the intestinal cells of an animal?
A) Sodium and glucose compete for the same binding site in the cotransporter.
B) Glucose entering the cell down its concentration gradient provides energy for uptake of sodium ions against the electrochemical gradient.
C) Sodium ions can move down their electrochemical gradient through the cotransporter whether or not glucose is present outside the cell.
D) A substance that blocks sodium ions from binding to the cotransport protein will also block the transport of glucose.
50) Proton pumps are used in various ways by members of every domain of organisms: Bacteria, Archaea, and Eukarya. What does this most probably mean?
A) Proton gradients across a membrane were used by cells that were the common ancestor of all three domains of life.
B) The high concentration of protons in the ancient atmosphere must have necessitated a pump mechanism.
C) Cells of each domain evolved proton pumps independently when oceans became more acidic. D) Proton pumps are necessary to all cell membranes.
51) Several epidemic microbial diseases of earlier centuries incurred high death rates because they resulted in severe dehydration due to vomiting and diarrhea. Today they are usually not fatal because we have developed which of the following?
A) antiviral medications that are efficient and work well with most viruses
B) intravenous feeding techniques
C) medications to slow blood loss
D) hydrating drinks with high concentrations of salts and glucose
52) The force driving simple diffusion is _____, while the energy source for active transport is _____.
A) the concentration gradient; ADP
B) the concentration gradient; ATP
C) transmembrane pumps; electron transport
D) phosphorylated protein carriers; ATP
53) An organism with a cell wall would most likely be unable to take in materials through _____.
B) active transport
D) facilitated diffusion
54) White blood cells engulf bacteria using _____.
D) receptor-mediated exocytosis
55) Familial hypercholesterolemia is characterized by _____.
A) defective LDL receptors on the cell membranes
B) poor attachment of the cholesterol to the extracellular matrix of cells
C) a poorly formed lipid bilayer that cannot incorporate cholesterol into cell membranes D) inhibition of the cholesterol active transport system in red blood cells
56) The difference between pinocytosis and receptor-mediated endocytosis is that _____.
A) pinocytosis brings only water molecules into the cell, but receptor-mediated endocytosis brings in other molecules as well.
B) pinocytosis increases the surface area of the plasma membrane, whereas receptor-mediated endocytosis decreases the plasma membrane surface area.
C) pinocytosis is nonselective in the molecules it brings into the cell, whereas receptor-mediated endocytosis offers more selectivity.
D) pinocytosis can concentrate substances from the extracellular fluid, but receptor-mediated endocytosis cannot.
57) In receptor-mediated endocytosis, receptor molecules initially project to the outside of the cell. Where do they end up after endocytosis?
A) on the outside of vesicles
B) on the inside surface of the cell membrane
C) on the inside surface of the vesicle
D) on the outer surface of the nucleus
58) A bacterium engulfed by a white blood cell through phagocytosis will be digested by enzymes contained in _____.
B) Golgi vesicles
D) secretory vesicles
59) In an HIV-infected cell producing HIV virus particles, the viral glycoprotein is expressed on the plasma membrane. How do the viral glycoproteins get to the plasma membrane? They are synthesized _____.
A) on ribosomes on the plasma membrane
B) by ribosomes in the rough ER and arrive at the plasma membrane in the membrane of secretory vesicles
C) on free cytoplasmic ribosomes and then inserted into the plasma membrane
D) by ribosomes in the rough ER, secreted from the cell, and inserted into the plasma membrane from the outside
60) What would be observed by live-cell fluorescence microscopy immediately after HIV entry if HIV is endocytosed first, and then later fuses with the endocytotic vesicle membrane?
A) A spot of red fluorescence will be visible on the infected cell's plasma membrane, marking the site of membrane fusion and HIV entry.
B) The red fluorescent dye-labeled lipids will appear in the infected cell's interior.
C) A spot of red fluorescence will diffuse in the infected cell's cytoplasm.
D) A spot of red fluorescence will remain outside the cell after delivering the viral capsid.
Sets found in the same folder
Biology Chapter 8
Campbell Biology; Tenth Edition; Chapter…
Campbell Biology; Tenth Edition; Chapter…
Campbell Biology; Tenth Edition; Chapter 11; Cell…
Sets with similar terms
Biology 111- Chapter 7
Chapter 7 - Membrane Structure and Function
Bio - Ch. 7
Other sets by this creator
Biology Chapter 9
Biology Lab Practical 1