mastering bio chapter 5 quiz

When placed in a hypotonic environment, where the solute concentration is below that of the cell, a houseplant will _____. -go brown at the edges of its leaves -die -remain standing upright -go limp and lifeless

remain standing upright

The plasma membrane is selectively permeable. Which of the following can pass freely through the membrane with no assistance? -sodium and hydrogen ions -glucose and lactose -oxygen and carbon dioxide -starch and cellulose

oxygen and carbon dioxide

Taq polymerase is an enzyme isolated from the organism Thermophilus aquaticus. This organism has been found living in the hot springs of Yellowstone National Park. This enzyme is used to copy human DNA from crime scenes. Most reactions are performed at ranges similar to those of the human body; however, what considerations should be made for optimum use of this enzyme? -The temperature should be raised. -The enzyme will not work on human DNA. -Nothing should be altered. -The pH should be decreased.

the temperature should be raised

Which of the following is a difference between active transport and facilitated diffusion? -Active transport involves transport proteins, and facilitated diffusion does not. -Facilitated diffusion involves transport proteins, and active transport does not. -Facilitated diffusion can move solutes against a concentration gradient, and active transport cannot. -Active transport requires the expenditure of cellular energy, and facilitated diffusion does not.

active transport requires the expenditure of cellular energy, and facilitated diffusion does not.

Which of these statements about enzyme inhibitors is true? -The action of competitive inhibitors may be reversible or irreversible. -When the product of an enzyme or a series of enzyme-catalyzed reactions acts as its inhibitor, this is known as positive feedback. -A noncompetitive inhibitor does not change the shape of the active site. -A competitive inhibitor binds to the enzyme outside the active site.

the action of competitive inhibitors may be reversible or irreversible

Which of these statements describes what occurs in facilitated diffusion? -Facilitated diffusion requires energy from the cell to drive a concentration gradient. -Facilitated diffusion of solutes occurs through protein pores in the membrane. -Facilitated diffusion of solutes occurs through phospholipid pores in the membrane. -Facilitated diffusion is another name for osmosis.

facilitated diffusion of solutes occurs through protein pores in the membrane

Utah's Great Salt Lake has an average salinity seven times higher than that of the oceans. Very few multicellular organisms live in this harsh environment. An example is the brine shrimp, which must devote a large portion of its metabolic energy to osmoregulation. These brine shrimp must _____. -actively pump water back into their cells to counter its loss due to osmosis -actively pump salt back out of their cells to counter its inflow due to osmosis -actively pump water back out of their cells to counter its inflow due to osmosis -synthesize membranes that are impermeable to substances that upset osmotic balance

actively pump water back into their cells to counter its loss due to osmosis

Antibiotics - for example, penicillin - cannot be used to treat viral infections, such as the common cold. Why? -They may poison the patient. -Antibiotics inhibit enzymes that are essential to the survival of bacteria only, not enzymes important to humans. -Only protease inhibitors can be used to fight viral infections. -Antibiotics enhance viral function.

antibiotics inhibit enzymes that are essential to the survival of bacteria only, not enzymes important to humans

During enzymatic reactions, substrates are converted to products. A property of enzymes that facilitates this reaction is that they are catalysts and therefore _____. -provide activation energy for the reactions they facilitate -can make an endergonic reaction exergonic -are proteins -change the rate of a reaction without being consumed by the reaction

change the rate of reaction without being consumed by the reaction

Azidothymidine (AZT) is an antiretroviral drug used in the treatment of HIV. It shares a structural similarity to a nucleotide. What might be the mode of action for this drug? -feedback inhibition -mixed inhibition -competitive inhibition -noncompetitive inhibition

competitive inhibition

Frequently, transplanted organs are rejected by the recipient's body. How is this reaction related to plasma membranes? -Everyone's organs contain different amounts of cholesterol. -The phospholipid bilayers become disrupted during transplant and may never re-form, causing the tissues to lose their function. -Each person has a unique set of carbohydrate chains attached to his or her plasma membranes. -The fibers of the extracellular matrix differ from individual to individual.

each person has a unique set of carbohydrate chains attached to his or her plasma membranes

Which statement regarding enzyme function is true? -Excessive salt ions can cause an enzyme to denature. -Most coenzymes are inorganic substances such as ions of iron or potassium. -Enzymes cannot function at a pH lower than 6. -Higher temperatures allow greater contact between enzymes and substrates; therefore, the higher the temperature the better the enzyme will function.

excessive salt ions can cause an enzyme to denature

Why doesn't the antibiotic penicillin harm humans? -The dosage given to kill bacteria is too low to harm humans. -Penicillin attacks plasma membranes. -Penicillin attacks the nervous system. -Human cells do not have cell walls.

human cells do not have cell walls

The concentration of solutes in a red blood cell is about 2%. Sucrose cannot pass through the membrane, but water and urea can. Osmosis would cause red blood cells to shrink the most when immersed in which of the following solutions? -a hypertonic urea solution -a hypertonic sucrose solution -a hypotonic urea solution -a hypotonic sucrose solution

hypertonic sucrose solution

Review the figure below of passive transport, then choose one of the following statements as being descriptive of this process. -Passive transport requires energy from the cell to move molecules from an area of high concentration to an area of lower concentration. -Passive transport can transport molecules without the assistance of proteins from an area of high concentration to an area of lower concentration. -Passive transport works with the help of proteins to bring molecules from an area of low concentration to an area of higher concentration. -Passive transport always requires the help of proteins to bring molecules from an area of high concentration to an area of lower concentration.

passive transport can transport molecules without the assistance of proteins from an area of high concentration to an area of lower concentration

For an enzyme to catalyze a reaction there must be a specific fit between the __________ and the enzyme's __________. -enzyme ... active site -cofactor ... coenzyme -substrate ... active site -substrate ... product

substrate ... active site

The transport of molecules of a particular solute from inside an animal cell across the cell membrane to the extracellular fluid always requires energy when _____. -the lipid bilayer is permeable to the solute -a transport protein is involved in the movement of the molecules -the concentration of the solute is lower inside the cell than outside it -the concentration of the solute is higher inside the cell than outside it

the concentration of the solute is lower inside the cell than outside it.

Osmosis is often viewed incorrectly as a process driven directly by differences in solute concentration across a selectively permeable membrane. What really drives osmosis? -the first law of thermodynamics -the difference in sugar or ion concentration across a selectively permeable membrane -the difference in the height of water columns on either side of a selectively permeable membrane -the difference in water concentration across a selectively permeable membrane

the difference in water concentration across a selectively permeable membrane

What controls the net direction of molecules, such as oxygen, involved in passive transport? -the direction of the oxygen concentration gradient -the type of cell to or from which the oxygen molecule is moving -the size of the oxygen molecule -the amount of energy available to transport oxygen

the direction of the oxygen concentration gradient