CH5-METABOLISM

A major function of glycoproteins and glycolipids in the cell membrane is to A) glue cells together to form tissues. B) allow the cells of an embryo to sort themselves into tissues and organs. C) attach the cell membrane to the cytoskeleton. D) help the cell resist swelling. E) help the cell retain its shape.

B

A steer must eat at least 100 pounds of grain to gain less than 10 pounds of muscle tissue. This illustrates A) the first law of thermodynamics. B) the second law of thermodynamics. C) that some energy is destroyed in every energy conversion. D) that energy transformations are typically 100% efficient. E) None of the choices are correct.

B

Certain cells that line the stomach synthesize a digestive enzyme and secrete it into the stomach. This enzyme is a protein. Which of the following processes could be responsible for its secretion? A) endocytosis B) exocytosis C) diffusion D) pinocytosis E) passive transport

B

Where are eukaryotic cell enzymes typically located? A) in cell membranes B) inside organelles C) outside of the cell D) within the cytoskeleton E) in cell membranes and inside organelles

E

Which of the following can affect the rate of an enzyme-catalyzed reaction? A) temperature B) pH C) competitive inhibitors D) noncompetitive inhibitors E) All of the choices are correct.

E

Which of the following energy transfers is impossible in living systems? A) light energy to chemical energy B) chemical energy to kinetic energy C) potential energy to kinetic energy D) light energy to potential energy E) heat to light energy.

E

Which of the following energy transfers is/are possible in living systems? A) light energy to chemical energy B) chemical energy to kinetic energy C) potential energy to kinetic energy D) light energy to potential energy E) All of the choices are correct

E

Which of the following is a typical feature of an ATP-driven active transport mechanism? A) The transport protein must cross to the correct side of the membrane before the solute can bind to it. B) The solute must be phosphorylated before it can bind to the transport protein. C) The transport protein is irreversibly phosphorylated as transport takes place. D) The transport protein catalyzes the conversion of ADP to ATP. E) The solute moves against the concentration gradient

E

A plant cell in a hypotonic solution A) is turgid. B) lyses. C) shrivels. D) wilts. E) is flaccid.

A

ATP can be used as the cell's energy exchange mechanism because A) endergonic reactions can be fueled by coupling them with the formation of ATP from ADP. B) ATP is the most energy-rich small molecule in the cell. C) endergonic reactions can be fueled by coupling them with the hydrolysis of high-energy phosphate bonds in ATP. D) the regeneration of ATP from ADP can be fueled by coupling it with endergonic reactions. E) ATP is a disposable form of chemical energy, used once and then discarded by the cell.

A

Anything that prevents ATP formation will most likely A) result in cell death. B) force the cell to rely on lipids for energy. C) result in the conversion of kinetic energy to potential energy. D) force the cell to rely on ADP for energy. E) have no effect on the cell.

A

In a hypotonic solution, an animal cell will A) lyse. B) experience turgor. C) neither gain nor lose water. D) shrivel. E) lose water

A

Relaying a message from a membrane receptor to a molecule that performs a specific function within a cell is called A) signal transduction. B) inhibition. C) competition. D) self-recognition. E) selective permeability.

A

Small, nonpolar, hydrophobic molecules such as fatty acids A) easily pass through a membrane's lipid bilayer. B) very slowly diffuse through a membrane's lipid bilayer. C) require transport proteins to pass through a membrane's lipid bilayer. D) are actively transported across cell membranes. E) usually enter the cell via endocytosis.

A

When a cell uses chemical energy to perform work, it couples a(n) ________ reaction with a(n) ________ reaction. A) exergonic . . . endergonic B) endergonic . . . exergonic C) exergonic . . . spontaneous D) spontaneous . . . exergonic E) endergonic . . . spontaneous

A

When two aqueous solutions that differ in solute concentration are placed on either side of a semipermeable membrane, and osmosis is allowed to take place, the water will A) exhibit a net movement to the side with lower water concentration. B) exhibit a net movement to the side with higher water concentration. C) exhibit a net movement to the side with lower solute concentration. D) exhibit an equal movement in both directions across the membrane. E) not cross the membrane.

A

Which one of the following processes could result in the net movement of a substance into a cell, if the substance is more concentrated in the cell than in the surroundings? A) active transport B) facilitated diffusion C) diffusion D) osmosis E) None of the choices are correct

A

Most of the functions of a cell membrane are performed by A) glycolipids. B) proteins. C) phospholipids. D) cholesterol. E) nucleotides

B

Phagocytosis is to eating as pinocytosis is to A) osmosis. B) drinking. C) chewing. D) hydrolysis. E) lysis.

B

Some protozoans have special organelles called contractile vacuoles that continually eliminate excess water from the cell. The presence of these organelles tells you that the environment A) is isotonic to the protozoan. B) is hypotonic to the protozoan. C) is hypertonic to the protozoan. D) contains a higher concentration of solutes than the protozoan. E) None of the choices are correct.

B

The "flip-flop" of phospholipids within the cell membrane is a very frequent occurrence. A) True B) False

B

Which characteristic promoted the utilization of lipids as the first cell membrane? A) spontaneous degradation of the intracellular environment B) self-assembly into a simple membrane C) ability to form an impermeable membrane D) formation of a semi-solid membrane E) utilization of the hydrophilic nature of lipids

B

Which of the following is a coenzyme? A) zinc B) vitamin B6 C) iron D) iodine E) hydrogen ions

B

Bacterial production of the enzymes needed for the synthesis of the amino acid tryptophan declines with increasing levels of tryptophan and increases as tryptophan levels decline. This is an example of A) competitive inhibition. B) noncompetitive inhibition. C) feedback inhibition. D) positive feedback. E) irreversible inhibition.

C

Cells acquire LDLs by A) osmosis. B) diffusion. C) receptor-mediated endocytosis. D) pinocytosis. E) phagocytosis

C

Facilitated diffusion across a biological membrane requires __________ and moves a substance __________ its concentration gradient. A) energy and transport proteins . . . down B) energy . . . down C) transport proteins . . . down D) energy and transport proteins . . . against E) transport proteins . . . against

C

Living systems A) violate the first law of thermodynamics. B) violate the second law of thermodynamics. C) decrease their entropy while increasing the entropy of the universe. D) are examples of a closed system. E) None of the choices are correct.

C

Which of the following pieces of evidence would prove that a substance enters a cell by active rather than passive transport? A) The substance is moved across the cell membrane by a carrier protein. B) The substance enters the cell when its concentration is higher outside the cell than inside. C) The breakdown of ATP is needed for transport to occur. D) All of the choices are correct. E) None of the choices are correct.

C

Which of the following statements concerning energy is false? A) Fireflies are able to take potential energy in the form of food and convert that energy into kinetic energy in the form of heat and light. B) A gasoline engine converts chemical energy into kinetic energy. C) Living systems convert heat energy into chemical energy to reduce entropy. D) Energy transformations in cells are accompanied by the release of heat energy. E) During photosynthesis, plants convert kinetic energy into chemical energy.

C

Which of the following substances could be a cofactor? A) a protein B) a polypeptide C) a zinc atom D) a ribosome E) collagen

C

Which one of the following processes is endergonic? A) the burning of wood B) the release of heat from the breakdown of glucose C) the synthesis of glucose from carbon dioxide and water D) the breakdown of glucose E) cellular respiration

C

Which one of the following is true? A) Enzymes are inorganic. B) An enzyme's function is unaffected by changes in pH. C) Enzymes are the reactants in a chemical reaction. D) Enzymes catalyze specific reactions. E) All enzymes depend on protein cofactors to function.

D

An energy barrier A) is the amount of energy that must be produced by the reactants to start a chemical reaction. B) is higher than the energy of activation of a reaction. C) is lower than the energy of activation of a reaction. D) prevents the spontaneous decomposition of molecules in the cell. E) can only be overcome with the use of enzymes.

D

How does inhibition of an enzyme-catalyzed reaction by a competitive inhibitor differ from inhibition by a noncompetitive inhibitor? A) Competitive inhibitors interfere with the enzyme; noncompetitive inhibitors interfere with the reactants. B) Competitive inhibitors bind to the enzyme reversibly; noncompetitive inhibitors bind to it irreversibly. C) Competitive inhibitors change the enzyme's tertiary structure; noncompetitive inhibitors cause polypeptide subunits to dissociate. D) Competitive inhibitors bind to the active site of the enzyme; noncompetitive inhibitors bind to a different site. E) Competitive inhibitors are inorganic substances such as metal ions; noncompetitive inhibitors are vitamins or vitamin derivatives.

D

Kinetic energy differs from chemical energy in that A) kinetic energy is stored energy that has the potential to do work, and chemical energy is the energy of movement. B) kinetic energy depends on the movement of atoms, whereas chemical energy depends on the movement of molecules. C) kinetic energy can be converted into various forms of energy, whereas chemical energy can only be converted into heat. D) kinetic energy is the energy of a moving object, whereas chemical energy is the potential energy of molecules. E) chemical energy is a particular form of kinetic energy.

D

Malathion and tetracycline are both enzyme inhibitors. Malathion is used to kill insects; tetracycline to kill bacteria. Malathion is more toxic to human cells than is tetracycline. Which of the following explanations for the difference in toxicity to human cells would be reasonable? A) Malathion is a competitive inhibitor; tetracycline is a noncompetitive inhibitor. B) Malathion binds to its enzyme reversibly; tetracycline binds to its enzyme irreversibly. C) Human cells do not contain the enzymes inhibited by malathion or tetracycline. D) Human cells contain the enzymes inhibited by both compounds, but the enzyme inhibited by tetracycline is not metabolically crucial. E) None of the choices are correct.

D

Which of the following statements about the ATP molecule is true? A) It contains two phosphate groups. B) Extremely stable bonds link the second and third phosphate groups. C) It contains the six-carbon sugar hexose. D) It contains a nitrogenous base molecule called adenine. E) It can be coupled with an exergonic reaction.

D

Which of the following substances would have the most trouble crossing a biological membrane by diffusing through the lipid bilayer? A) H2O B) O2 C) CO2 D) Na+ E) a small, nonpolar molecule such as butane (C4H10)

D

White blood cells (WBCs) are more resistant to lysis than red blood cells (RBCs). When looking at a sample of blood for WBCs, would could you do to reduce interference from RBCs? A) Mix the blood in a salty solution to cause the RBCs to lyse. B) Mix the blood in an isotonic solution and allow the WBCs to float to the top. C) Mix the blood with a dye that stains the proteins in the cytoplasm. D) Mix the blood in a hypotonic solution, which will cause the RBCs to lyse. E) Mix the blood in a hypertonic solution, which will cause the RBCs to lyse.

D

All cells are enclosed by a plasma membrane that is similar in ________ and ________. A) thickness . . . composition B) permeability . . . content C) proteins . . . lipids D) lucidity . . . texture E) structure . . . function

E

If placed in tap water, an animal cell will undergo lysis, whereas a plant cell will not. What accounts for this difference? A) expulsion of water by the plant cell's central vacuole B) the relative impermeability of the plant cell membrane to water C) the relative impermeability of the plant cell wall to water D) the fact that plant cells are isotonic to tap water E) the relative inelasticity and strength of the plant cell wall

E

Membrane phospholipids A) have hydrophobic heads that face the center of the membrane and are shielded from water. B) have hydrophilic tails that face outward and are exposed to water. C) often have "kinks" in their tails caused by the presence of a single rather than a double bond between carbons. D) remain fluid because they are tightly packed against one another. E) None of the choices are correct.

E

Substrates bind to an enzyme's ________ site. A) reactant B) allosteric C) regulatory D) phosphate E) active

E

Which of the following statements regarding thermodynamics is false? A) Thermodynamics is the study of energy transformations that occur in a collection of matter. B) The collection of matter under study is called the system. C) A single cell or the planet Earth could be a thermodynamic system. D) An open system exchanges both energy and matter with its surroundings. E) An automobile engine is an example of a closed system

E

Which of the following will have no effect on the rate of an enzyme-catalyzed reaction? A) temperature B) pH C) competitive inhibitors D) noncompetitive inhibitors E) net change in energy

E