Ch. 5 Bio 101

Many of the enzymes that control a firefly's ability to produce light energy from chemical energy are located

a. within mitochondria.

b. in membranes.

c. outside of cells.

d. within chloroplasts.

e. in the nucleus.

b. In membranes

Kinetic energy differs from chemical energy in that

a. chemical energy is a particular form of kinetic energy.

b. kinetic energy depends on the movement of atoms, whereas chemical energy depends on the movement of molecules.

c. kinetic energy is the energy of a moving object, whereas chemical energy is the potential energy of molecules.

d. kinetic energy is stored energy that has the potential to do work, and chemical energy is the energy of movement.

e. kinetic energy can be converted into various forms of energy, whereas chemical energy can only be converted into heat.

C. kinetic energy is the energy of a moving object, whereas chemical energy is the potential energy of molecules

Glucose molecules provide energy to power the swimming motion of sperm. In this example, the sperm are changing

a. chemical energy into potential energy.

b. None of the choices are correct.

c. chemical energy into kinetic energy.

d. kinetic energy into potential energy.

e. kinetic energy into chemical energy.

C. chemical energy into kinetic energy

Which one of the following is not true?

a. Thermodynamics is the study of energy transformations that occur in a collection of matter.

b. An automobile engine is an example of a closed system.

c. The collection of matter under study is called the system.

d. A single cell or the planet Earth could be a thermodynamic system.

e. An open system exchanges both energy and matter with its surroundings.

b. An automobile engine is an example of a closed system.

According to __________, energy cannot be created or destroyed.
Selected Answer:
a. the first law of thermodynamics
Answers:
a. the first law of thermodynamics

b. Einstein's law of relativity

c. the third law of thermodynamics

d. the second law of thermodynamics

e. Aristotle's first principle

A. first law of thermodynamics

A steer must eat at least 100 pounds of grain to gain less than 10 pounds of muscle tissue. This illustrates

a. that energy transformations are typically 100% efficient.

b. the first law of thermodynamics.

c. None of the choices are correct.

d. the second law of thermodynamics.

e. that some energy is destroyed in every energy conversion.

D. second law of thermodynamics

Which of the following energy transfers is/are possible in living systems?

a. light energy to chemical energy

b. light energy to potential energy

c. chemical energy to kinetic energy

d. potential energy to kinetic energy

e. All of the choices are correct.

e. All of the choices are correct.

Living systems

a. None of the choices are correct.

b. are examples of a closed system.

c. violate the second law of thermodynamics.

d. decrease their entropy while increasing the entropy of the universe.

e. violate the first law of thermodynamics.

d. decrease their entropy while increasing the entropy of the universe.

Which one of the following processes is endergonic?

a. the release of heat from the breakdown of glucose

b. the burning of wood

c. cellular respiration

d. the synthesis of glucose from carbon dioxide and water

e. the breakdown of glucose to power ATP formation

d. the synthesis of glucose from carbon dioxide and water

What is the basic difference between exergonic and endergonic reactions?

a. Exergonic reactions involve the breaking of bonds; endergonic reactions involve the formation of bonds.

b. Exergonic reactions release energy; endergonic reactions absorb it.

c. In exergonic reactions, the reactants have less chemical energy than the products; in endergonic reactions, the opposite is true.

d. Exergonic reactions involve the formation of bonds; endergonic reactions involve the breaking of bonds.

e. Exergonic reactions involve ionic bonds; endergonic reactions involve covalent bonds.

b. Exergonic reactions release energy; endergonic reactions absorb it.

Which one of the following statements concerning energy is not true?

a. Energy transformations in cells are accompanied by the release of heat energy.

b. A gasoline engine converts chemical energy into kinetic energy.

c. During photosynthesis, plants convert kinetic energy into chemical energy.

d. 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.

e. Living systems convert heat energy into chemical energy to reduce entropy.

e. Living systems convert heat energy into chemical energy to reduce entropy.

The transfer of a phosphate group to a molecule or compound is called

a. carboxylation.

b. hydrogenation.

c. phosphorylation.

d. hydrogen bonding.

e. ionization.

c. phosphorylation.

Anything that prevents ATP formation will most likely

a. force the cell to rely on lipids for energy.

b. force the cell to rely on ADP for energy.

c. have no effect on the cell.

d. result in the conversion of kinetic energy to potential energy.

e. result in cell death.

e. result in cell death.

When a cell uses chemical energy to perform work, it couples a(n) __________ reaction with a(n) __________ reaction.

a. spontaneous . . . exergonic

b. exergonic . . . spontaneous

c. endergonic . . . exergonic

d. exergonic . . . endergonic

e. endergonic . . . spontaneous

d. exergonic . . . endergonic

Which one of the following is true about the ATP molecule?

a. It contains the six-carbon sugar hexose.

b. Extremely stable bonds link the second and third phosphate groups.

c. It contains two phosphate groups.

d. None of the choices are correct.

e. It contains a nitrogenous base molecule called adenine.

e. It contains a nitrogenous base molecule called adenine.

ATP can be used as the cell's energy currency because

a. endergonic reactions can be fueled by coupling them with the hydrolysis of high-energy phosphate bonds in ATP.

b. ATP is the most energy-rich small molecule in the cell.

c. endergonic reactions can be fueled by coupling them with the formation of ATP from ADP.

d. None of the choices are correct.

e. the regeneration of ATP from ADP can be fueled by coupling it with endergonic reactions.

a. endergonic reactions can be fueled by coupling them with the hydrolysis of high-energy phosphate bonds in ATP.

An energy barrier

a. prevents the spontaneous decomposition of ATP in the cell.

b. is higher than the energy of activation of a reaction.

c. is the amount of energy that must be produced by the reactants to start a chemical reaction.

d. is lower than the energy of activation of a reaction.

e. None of the choices are correct.

a. prevents the spontaneous decomposition of ATP in the cell.

Most of a cell's enzymes are

a. proteins.

b. carbohydrates.

c. lipids.

d. nucleic acids.

e. amino acids.

a. proteins.

When an enzyme catalyzes a reaction

a. it acts as a reactant.

b. it lowers the activation energy of the reaction.

c. it raises the activation energy of the reaction.

d. None of the choices are correct.

e. it becomes a product.

b. it lowers the activation energy of the reaction.

The active site of an enzyme is

a. the region of a substrate that is changed by an enzyme.

b. the highly changeable portion of an enzyme that adapts to fit the substrates of various reactions.

c. the region of an enzyme that attaches to a substrate.

d. the region of a product that detaches from the enzyme.

e. None of the choices are correct.

c. the region of an enzyme that attaches to a substrate.

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. Enzymes are used up in chemical reactions.

e. Enzymes are used up in chemical reactions.

Which of the following substances could be a cofactor?

a. a polypeptide

b. a protein

c. a ribosome

d. a zinc atom

e. None of the choices are correct.

d. a zinc atom

A child is brought to the hospital with a fever of 107F. Doctors immediately order an ice bath to lower the child's temperature. Which explanation offers the most logical reason for this action?

a. Elevated body temperatures may denature enzymes. This would interfere with the cell's abilities to catalyze various reactions.

b. Elevated body temperature will increase reaction rates in the child's cells and overload the limited number of enzymes found in the cell.

c. Elevated body temperatures will increase the energy of activation needed to start various chemical reactions in the body. This will interfere with the ability of enzymes to catalyze vital chemical reactions.

d. Elevated body temperatures easily break the covalent bonds linking biologically important molecules. This will cause a general breakdown of cell structures.

e. Elevated body temperatures cause molecules to vibrate more quickly and prevent enzymes from easily attaching to reactants. This would slow vital body reactions.

a. Elevated body temperatures may denature enzymes. This would interfere with the cell's abilities to catalyze various reactions.

Heating inactivates enzymes by

a. changing the enzyme's three-dimensional shape.

b. breaking the covalent bonds that hold the molecule together.

c. removing phosphate groups from the enzyme.

d. causing enzyme molecules to stick together.

e. None of the choices are correct

a. changing the enzyme's three-dimensional shape.

Which of the following is a coenzyme?

a. iodine

b. vitamin B6

c. zinc

d. iron

e. hydrogen ions

b. vitamin B6

Which of the following can affect the rate of an enzyme-catalyzed reaction?

a. All of the choices are correct.

b. noncompetitive inhibitors

c. temperature

d. competitive inhibitors

e. pH

a. All of the choices are correct

Inhibition of an enzyme is irreversible when

a. a noncompetitive inhibitor is involved.

b. None of the choices are correct.

c. the shape of the enzyme is changed.

d. covalent bonds form between inhibitor and enzyme.

e. a competitive inhibitor is involved.

d. covalent bonds form between inhibitor and enzyme.

How does inhibition of an enzyme-catalyzed reaction by a competitive inhibitor differ from inhibition by a noncompetitive inhibitor?

a. Competitive inhibitors bind to the active site of the enzyme; noncompetitive inhibitors bind to a different site.

b. Competitive inhibitors interfere with the enzyme; noncompetitive inhibitors interfere with the reactants.

c. Competitive inhibitors bind to the enzyme reversibly; noncompetitive inhibitors bind to it irreversibly.

d. Competitive inhibitors change the enzyme's tertiary structure; noncompetitive inhibitors cause polypeptide subunits to dissociate.

e. Competitive inhibitors are inorganic substances such as metal ions; noncompetitive inhibitors are vitamins or vitamin derivatives.

a. Competitive inhibitors bind to the active site of the enzyme; noncompetitive inhibitors bind to a different site.

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. negative feedback.

b. competitive inhibition.

c. irreversible inhibition.

d. positive feedback.

e. noncompetitive inhibition.

a. negative feedback

A medical research team is concerned about the outbreak of a new disease in humans. The bacteria that cause the disease resemble bacteria that cause a similar disease in cattle. The bovine disease is treated with a drug that inhibits a bacterial enzyme crucial to bacterial cell division. As the researchers prepare to test the drug in humans, they will

a. be fairly confident about its safety; bacterial enzymes are all very different from human enzymes, so the drug should only affect the bacteria.

b. be fairly confident about its safety; although bacteria produce all of the same enzymes as human cells, the small size of bacteria make them more susceptible to damage.

c. None of the choices are correct.

d. be concerned about its safety; since all living cells contain the same enzymes, the drug is likely to cause cell damage; the question is whether the damage is too large to be tolerated.

e. be uncertain about its safety; human cells contain some enzymes that are very similar to those found in bacterial cells; the drug may inhibit these enzymes and damage the human cells.

a. be fairly confident about its safety; bacterial enzymes are all very different from human enzymes, so the drug should only affect the bacteria.

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. None of the choices are correct.

c. Malathion binds to its enzyme reversibly; tetracycline binds to its enzyme irreversibly.

d. Human cells do not contain the enzymes inhibited by malathion or tetracycline.

e. Human cells contain the enzymes inhibited by both compounds, but the enzyme inhibited by malathion is not metabolically crucial.

e. Human cells contain the enzymes inhibited by both compounds, but the enzyme inhibited by malathion is not metabolically crucial

Where are eukaryotic cell enzymes typically located?

a. in cell membranes

b. outside of the cell

c. in cell membranes and inside organelles

d. inside organelles

e. within the cytoskeleton

c. in cell membranes and inside organelles

Plasma membranes are selectively permeable. This means that

a. cholesterol cannot enter the cell.

b. plasma membranes must be very thick.

c. the plasma membrane regulates the passage of material into and out of the cell.

d. anything can pass into or out of a cell.

e. glucose cannot enter the cell.

c. the plasma membrane regulates the passage of material into and out of the cell.

Which one of the following is not a function of the plasma membrane? The plasma membrane

a. forms a selective barrier around the cell.

b. has receptors for chemical messages.

c. plays a role in signal transduction.

d. is the control center of the cell.

e. is involved in self-recognition.

... not A

Small, nonpolar, hydrophobic molecules such as fatty acids

a. are actively transported across cell membranes.

b. require transport proteins to pass through a membrane's lipid bilayer.

c. easily pass through a membrane's lipid bilayer.

d. usually enter the cell via endocytosis.

e. very slowly diffuse through a membrane's lipid bilayer.

c. easily pass through a membrane's lipid bilayer.

Membrane phospholipids

a. have hydrophilic tails that face outward and are exposed to water.

b. have hydrophobic heads that face the center of the membrane and are shielded from 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. None of the choices are correct.

Which one of the following substances would have the most trouble crossing a biological membrane by diffusing through the lipid bilayer?

a. CO2

b. O2

c. Na+

d. H2O

c. Na+

The fluid mosaic model describes the plasma membrane as consisting of

a. two layers of phospholipids with protein sandwiched between them.

b. individual proteins and phospholipids that can drift in a phospholipid bilayer.

c. carbohydrates, proteins, and phospholipids that can drift in the membrane.

d. a phospholipid bilayer with embedded carbohydrates.

e. a protein bilayer with embedded phospholipids.

b. individual proteins and phospholipids that can drift in a phospholipid bilayer.

The cholesterol associated with cell membranes

a. makes the cell membrane fluid at room temperature.

b. is an abnormality resulting from a diet high in cholesterol.

c. helps to stabilize the cell membrane at body temperature.

d. is attached to membrane proteins and extends into the watery environment surrounding the cell.

e. None of the choices are correct.

c. helps to stabilize the cell membrane at body temperature.

A major function of glycoproteins and glycolipids in the cell membrane is to

a. help the cell resist swelling.

b. help the cell retain its shape.

c. allow the cells of an embryo to sort themselves into tissues and organs.

d. attach the cell membrane to the cytoskeleton.

e. glue cells together to form tissues.

c. allow the cells of an embryo to sort themselves into tissues and organs.

When physicians perform an organ transplant, they choose a donor whose tissues match those of the recipient as closely as possible. Which of the following cell components are being matched?

a. plasma membrane cholesterols

b. cytoskeletal elements

c. cell-surface carbohydrates

d. plasma membrane proteins

e. plasma membrane phospholipids

c. cell-surface carbohydrates

Most of the functions of a cell membrane are performed by

a. phospholipids.

b. proteins.

c. nucleotides.

d. cholesterol.

e. glycolipids.

b. proteins.

Which one of the following is not a function of membrane proteins? Membrane proteins

a. attach the membrane to the cytoskeleton.

b. serve as enzymes.

c. provide cellular identification tags.

d. form junctions between cells.

e. All of the choices are membrane protein functions.

e. All of the choices are membrane protein functions.

Relaying a message from a membrane receptor to a molecule that performs a specific function within a cell is called

a. self-recognition.

b. competition.

c. signal transduction.

d. inhibition.

e. selective permeability.

c. signal transduction

Which of the following is not a true statement about diffusion? Diffusion

a. occurs when particles spread from areas where they are less concentrated to areas where they are more concentrated.

b. is a result of the kinetic energy of atoms and molecules.

c. requires no input of energy into the system.

d. proceeds until equilibrium is reached.

e. is driven by entropy.

a. occurs when particles spread from areas where they are less concentrated to areas where they are more concentrated

Diffusion does not require the cell to expend ATP. Therefore, diffusion is considered a type of

a. phagocytosis.

b. passive transport.

c. exocytosis.

d. endocytosis.

e. active transport.

b. passive transport.

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 an equal movement in both directions across the membrane.

b. exhibit a net movement to the side with lower water concentration.

c. exhibit a net movement to the side with higher water concentration.

d. not cross the membrane.

e. exhibit a net movement to the side with lower solute concentration.

b. exhibit a net movement to the side with lower water concentration.

In lab, you use a special balloon that is permeable to water but not sucrose to make an "artificial cell." The balloon is filled with a solution of 20% sucrose and 80% water and is immersed in a beaker containing a solution of 40% sucrose and 60% water. Which of the following will occur?

a. None of the choices will occur.

b. Sucrose will enter the balloon.

c. Water will enter the balloon.

d. Sucrose will leave the balloon.

e. Water will leave the balloon.

e. Water will leave the balloon.

In lab, you use a special balloon that is permeable to water but not sucrose to make an "artificial cell." The balloon is filled with a solution of 20% sucrose and 80% water and is immersed in a beaker containing a solution of 40% sucrose and 60% water. The solution in the balloon is __________ relative to the solution in the beaker.

a. hydrophobic

b. isotonic

c. hypertonic

d. hypotonic

e. hydrophilic

d. hypotonic

A cell that neither gains nor loses water when it is immersed in a solution is

a. metabolically inactive.

b. dead.

c. hypertonic to its environment.

d. hypotonic to its environment.

e. isotonic to its environment.

e. isotonic to its environment.

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 hypotonic to the protozoan.

b. is hypertonic to the protozoan.

c. None of the choices are correct.

d. is isotonic to the protozoan.

e. contains a higher concentration of solutes than the protozoan.

a. is hypotonic to the protozoan.

Osmosis can be defined as

a. active transport.

b. endocytosis.

c. the diffusion of nonpolar molecules.

d. the diffusion of water.

e. the diffusion of a solute.

d. the diffusion of water.

If placed in tap water, an animal cell will undergo lysis, whereas a plant cell will not. What accounts for this difference?

a. the relative impermeability of the plant cell membrane to water

b. the fact that plant cells are isotonic to tap water

c. the relative inelasticity and strength of the plant cell wall

d. expulsion of water by the plant cell's central vacuole

e. the relative impermeability of the plant cell wall to water

c. the relative inelasticity and strength of the plant cell wall

A plant cell in a hypotonic solution

a. is turgid.

b. lyses.

c. shrivels.

d. wilts.

e. is flaccid.

a. is turgid

You are adrift in the Atlantic Ocean, and, being thirsty, drink the surrounding seawater. As a result,

a. your cells lyse, due to the excessive intake of salt.

b. you quench your thirst.

c. None of the choices are correct.

d. you dehydrate yourself.

e. your cells become turgid.

d. you dehydrate yourself.

The organ that plays a major role in osmoregulation in humans is the

a. pancreas.

b. heart.

c. spleen.

d. kidney.

e. gallbladder.

d. kidney.

Facilitated diffusion across a biological membrane requires __________ and moves a substance __________ its concentration gradient.

a. energy . . . down

b. transport proteins . . . against

c. transport proteins . . . down

d. energy and transport proteins . . . against

e. energy and transport proteins . . . down

c. transport proteins . . . down

The molecules responsible for membrane transport are

a. ATP.

b. carbohydrates.

c. proteins.

d. phospholipids.

e. steroids.

c. proteins.

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. None of the choices are correct.

b. facilitated diffusion

c. osmosis

d. active transport

e. diffusion

d. active transport

Which one of the following is a typical feature of an ATP-driven active transport mechanism?

a. The solute must be phosphorylated before it can bind to the transport protein.

b. The transport protein must cross to the correct side of the membrane before the solute can bind to it.

c. None of the choices are correct.

d. The transport protein is irreversibly phosphorylated as transport takes place.

e. The transport protein catalyzes the conversion of ADP to ATP.

c. None of the choices are correct

Active transport

a. requires the cell to expend energy.

b. All of the choices are correct.

c. can move solutes up a concentration gradient.

d. uses ATP as an energy source.

e. can involve the coupled passage of solutes.

b. All of the choices are correct.

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. pinocytosis

b. diffusion

c. exocytosis

d. endocytosis

e. passive transport

c. exocytosis

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 breakdown of ATP is needed for transport to occur.

c. The substance enters the cell when its concentration is higher outside the cell than inside.

d. None of the choices are correct.

e. All of the choices are correct.

b. The breakdown of ATP is needed for transport to occur.

The act of a white blood cell engulfing a bacterium is

a. receptor-mediated endocytosis.

b. pinocytosis.

c. phagocytosis.

d. diffusion.

e. osmosis.

c. phagocytosis.

Phagocytosis is to eating as pinocytosis is to

a. lysis.

b. drinking.

c. chewing.

d. hydrolysis.

e. osmosis.

b. drinking.

Cells acquire LDLs by

a. pinocytosis.

b. receptor-mediated endocytosis.

c. diffusion.

d. phagocytosis.

e. osmosis.

b. receptor-mediated endocytosis.

An inherited lack (or shortage) of functional LDL receptors causes

a. hypercholesterolemia.

b. hyperbilirubinemia.

c. cystic fibrosis.

d. Marfan's syndrome.

e. type I diabetes.

a. hypercholesterolemia.

The ultimate source of nearly all energy available to life on Earth is

a. sunlight.

b. photosynthesis.

c. cellular respiration.

d. wind.

e. electricity.

a. sunlight.

Ultimately, nearly all animals are dependent on __________ as their source of energy.

a. electricity

b. photosynthesis

c. cellular respiration

d. heat

e. wind

b. photosynthesis

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Ch. 5 Bio 101

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Many of the enzymes that control a firefly’s ability to produce light energy from chemical energy are located

a. within mitochondria.

b. in membranes.

c. outside of cells.

d. within chloroplasts.

e. in the nucleus.

b. In membranes

Kinetic energy differs from chemical energy in that

a. chemical energy is a particular form of kinetic energy.

b. kinetic energy depends on the movement of atoms, whereas chemical energy depends on the movement of molecules.

c. kinetic energy is the energy of a moving object, whereas chemical energy is the potential energy of molecules.

d. kinetic energy is stored energy that has the potential to do work, and chemical energy is the energy of movement.

e. kinetic energy can be converted into various forms of energy, whereas chemical energy can only be converted into heat.

C. kinetic energy is the energy of a moving object, whereas chemical energy is the potential energy of molecules

Glucose molecules provide energy to power the swimming motion of sperm. In this example, the sperm are changing

a. chemical energy into potential energy.

b. None of the choices are correct.

c. chemical energy into kinetic energy.

d. kinetic energy into potential energy.

e. kinetic energy into chemical energy.

C. chemical energy into kinetic energy

Which one of the following is not true?

a. Thermodynamics is the study of energy transformations that occur in a collection of matter.

b. An automobile engine is an example of a closed system.

c. The collection of matter under study is called the system.

d. A single cell or the planet Earth could be a thermodynamic system.

e. An open system exchanges both energy and matter with its surroundings.

b. An automobile engine is an example of a closed system.

According to __________, energy cannot be created or destroyed.
Selected Answer:
a. the first law of thermodynamics
Answers:
a. the first law of thermodynamics

b. Einstein’s law of relativity

c. the third law of thermodynamics

d. the second law of thermodynamics

e. Aristotle’s first principle

A. first law of thermodynamics

A steer must eat at least 100 pounds of grain to gain less than 10 pounds of muscle tissue. This illustrates

a. that energy transformations are typically 100% efficient.

b. the first law of thermodynamics.

c. None of the choices are correct.

d. the second law of thermodynamics.

e. that some energy is destroyed in every energy conversion.

D. second law of thermodynamics

Which of the following energy transfers is/are possible in living systems?

a. light energy to chemical energy

b. light energy to potential energy

c. chemical energy to kinetic energy

d. potential energy to kinetic energy

e. All of the choices are correct.

e. All of the choices are correct.

Living systems

a. None of the choices are correct.

b. are examples of a closed system.

c. violate the second law of thermodynamics.

d. decrease their entropy while increasing the entropy of the universe.

e. violate the first law of thermodynamics.

d. decrease their entropy while increasing the entropy of the universe.

Which one of the following processes is endergonic?

a. the release of heat from the breakdown of glucose

b. the burning of wood

c. cellular respiration

d. the synthesis of glucose from carbon dioxide and water

e. the breakdown of glucose to power ATP formation

d. the synthesis of glucose from carbon dioxide and water

What is the basic difference between exergonic and endergonic reactions?

a. Exergonic reactions involve the breaking of bonds; endergonic reactions involve the formation of bonds.

b. Exergonic reactions release energy; endergonic reactions absorb it.

c. In exergonic reactions, the reactants have less chemical energy than the products; in endergonic reactions, the opposite is true.

d. Exergonic reactions involve the formation of bonds; endergonic reactions involve the breaking of bonds.

e. Exergonic reactions involve ionic bonds; endergonic reactions involve covalent bonds.

b. Exergonic reactions release energy; endergonic reactions absorb it.

Which one of the following statements concerning energy is not true?

a. Energy transformations in cells are accompanied by the release of heat energy.

b. A gasoline engine converts chemical energy into kinetic energy.

c. During photosynthesis, plants convert kinetic energy into chemical energy.

d. 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.

e. Living systems convert heat energy into chemical energy to reduce entropy.

e. Living systems convert heat energy into chemical energy to reduce entropy.

The transfer of a phosphate group to a molecule or compound is called

a. carboxylation.

b. hydrogenation.

c. phosphorylation.

d. hydrogen bonding.

e. ionization.

c. phosphorylation.

Anything that prevents ATP formation will most likely

a. force the cell to rely on lipids for energy.

b. force the cell to rely on ADP for energy.

c. have no effect on the cell.

d. result in the conversion of kinetic energy to potential energy.

e. result in cell death.

e. result in cell death.

When a cell uses chemical energy to perform work, it couples a(n) __________ reaction with a(n) __________ reaction.

a. spontaneous . . . exergonic

b. exergonic . . . spontaneous

c. endergonic . . . exergonic

d. exergonic . . . endergonic

e. endergonic . . . spontaneous

d. exergonic . . . endergonic

Which one of the following is true about the ATP molecule?

a. It contains the six-carbon sugar hexose.

b. Extremely stable bonds link the second and third phosphate groups.

c. It contains two phosphate groups.

d. None of the choices are correct.

e. It contains a nitrogenous base molecule called adenine.

e. It contains a nitrogenous base molecule called adenine.

ATP can be used as the cell’s energy currency because

a. endergonic reactions can be fueled by coupling them with the hydrolysis of high-energy phosphate bonds in ATP.

b. ATP is the most energy-rich small molecule in the cell.

c. endergonic reactions can be fueled by coupling them with the formation of ATP from ADP.

d. None of the choices are correct.

e. the regeneration of ATP from ADP can be fueled by coupling it with endergonic reactions.

a. endergonic reactions can be fueled by coupling them with the hydrolysis of high-energy phosphate bonds in ATP.

An energy barrier

a. prevents the spontaneous decomposition of ATP in the cell.

b. is higher than the energy of activation of a reaction.

c. is the amount of energy that must be produced by the reactants to start a chemical reaction.

d. is lower than the energy of activation of a reaction.

e. None of the choices are correct.

a. prevents the spontaneous decomposition of ATP in the cell.

Most of a cell’s enzymes are

a. proteins.

b. carbohydrates.

c. lipids.

d. nucleic acids.

e. amino acids.

a. proteins.

When an enzyme catalyzes a reaction

a. it acts as a reactant.

b. it lowers the activation energy of the reaction.

c. it raises the activation energy of the reaction.

d. None of the choices are correct.

e. it becomes a product.

b. it lowers the activation energy of the reaction.

The active site of an enzyme is

a. the region of a substrate that is changed by an enzyme.

b. the highly changeable portion of an enzyme that adapts to fit the substrates of various reactions.

c. the region of an enzyme that attaches to a substrate.

d. the region of a product that detaches from the enzyme.

e. None of the choices are correct.

c. the region of an enzyme that attaches to a substrate.

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. Enzymes are used up in chemical reactions.

e. Enzymes are used up in chemical reactions.

Which of the following substances could be a cofactor?

a. a polypeptide

b. a protein

c. a ribosome

d. a zinc atom

e. None of the choices are correct.

d. a zinc atom

A child is brought to the hospital with a fever of 107F. Doctors immediately order an ice bath to lower the child’s temperature. Which explanation offers the most logical reason for this action?

a. Elevated body temperatures may denature enzymes. This would interfere with the cell’s abilities to catalyze various reactions.

b. Elevated body temperature will increase reaction rates in the child’s cells and overload the limited number of enzymes found in the cell.

c. Elevated body temperatures will increase the energy of activation needed to start various chemical reactions in the body. This will interfere with the ability of enzymes to catalyze vital chemical reactions.

d. Elevated body temperatures easily break the covalent bonds linking biologically important molecules. This will cause a general breakdown of cell structures.

e. Elevated body temperatures cause molecules to vibrate more quickly and prevent enzymes from easily attaching to reactants. This would slow vital body reactions.

a. Elevated body temperatures may denature enzymes. This would interfere with the cell’s abilities to catalyze various reactions.

Heating inactivates enzymes by

a. changing the enzyme’s three-dimensional shape.

b. breaking the covalent bonds that hold the molecule together.

c. removing phosphate groups from the enzyme.

d. causing enzyme molecules to stick together.

e. None of the choices are correct

a. changing the enzyme’s three-dimensional shape.

Which of the following is a coenzyme?

a. iodine

b. vitamin B6

c. zinc

d. iron

e. hydrogen ions

b. vitamin B6

Which of the following can affect the rate of an enzyme-catalyzed reaction?

a. All of the choices are correct.

b. noncompetitive inhibitors

c. temperature

d. competitive inhibitors

e. pH

a. All of the choices are correct

Inhibition of an enzyme is irreversible when

a. a noncompetitive inhibitor is involved.

b. None of the choices are correct.

c. the shape of the enzyme is changed.

d. covalent bonds form between inhibitor and enzyme.

e. a competitive inhibitor is involved.

d. covalent bonds form between inhibitor and enzyme.

How does inhibition of an enzyme-catalyzed reaction by a competitive inhibitor differ from inhibition by a noncompetitive inhibitor?

a. Competitive inhibitors bind to the active site of the enzyme; noncompetitive inhibitors bind to a different site.

b. Competitive inhibitors interfere with the enzyme; noncompetitive inhibitors interfere with the reactants.

c. Competitive inhibitors bind to the enzyme reversibly; noncompetitive inhibitors bind to it irreversibly.

d. Competitive inhibitors change the enzyme’s tertiary structure; noncompetitive inhibitors cause polypeptide subunits to dissociate.

e. Competitive inhibitors are inorganic substances such as metal ions; noncompetitive inhibitors are vitamins or vitamin derivatives.

a. Competitive inhibitors bind to the active site of the enzyme; noncompetitive inhibitors bind to a different site.

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. negative feedback.

b. competitive inhibition.

c. irreversible inhibition.

d. positive feedback.

e. noncompetitive inhibition.

a. negative feedback

A medical research team is concerned about the outbreak of a new disease in humans. The bacteria that cause the disease resemble bacteria that cause a similar disease in cattle. The bovine disease is treated with a drug that inhibits a bacterial enzyme crucial to bacterial cell division. As the researchers prepare to test the drug in humans, they will

a. be fairly confident about its safety; bacterial enzymes are all very different from human enzymes, so the drug should only affect the bacteria.

b. be fairly confident about its safety; although bacteria produce all of the same enzymes as human cells, the small size of bacteria make them more susceptible to damage.

c. None of the choices are correct.

d. be concerned about its safety; since all living cells contain the same enzymes, the drug is likely to cause cell damage; the question is whether the damage is too large to be tolerated.

e. be uncertain about its safety; human cells contain some enzymes that are very similar to those found in bacterial cells; the drug may inhibit these enzymes and damage the human cells.

a. be fairly confident about its safety; bacterial enzymes are all very different from human enzymes, so the drug should only affect the bacteria.

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. None of the choices are correct.

c. Malathion binds to its enzyme reversibly; tetracycline binds to its enzyme irreversibly.

d. Human cells do not contain the enzymes inhibited by malathion or tetracycline.

e. Human cells contain the enzymes inhibited by both compounds, but the enzyme inhibited by malathion is not metabolically crucial.

e. Human cells contain the enzymes inhibited by both compounds, but the enzyme inhibited by malathion is not metabolically crucial

Where are eukaryotic cell enzymes typically located?

a. in cell membranes

b. outside of the cell

c. in cell membranes and inside organelles

d. inside organelles

e. within the cytoskeleton

c. in cell membranes and inside organelles

Plasma membranes are selectively permeable. This means that

a. cholesterol cannot enter the cell.

b. plasma membranes must be very thick.

c. the plasma membrane regulates the passage of material into and out of the cell.

d. anything can pass into or out of a cell.

e. glucose cannot enter the cell.

c. the plasma membrane regulates the passage of material into and out of the cell.

Which one of the following is not a function of the plasma membrane? The plasma membrane

a. forms a selective barrier around the cell.

b. has receptors for chemical messages.

c. plays a role in signal transduction.

d. is the control center of the cell.

e. is involved in self-recognition.

… not A

Small, nonpolar, hydrophobic molecules such as fatty acids

a. are actively transported across cell membranes.

b. require transport proteins to pass through a membrane’s lipid bilayer.

c. easily pass through a membrane’s lipid bilayer.

d. usually enter the cell via endocytosis.

e. very slowly diffuse through a membrane’s lipid bilayer.

c. easily pass through a membrane’s lipid bilayer.

Membrane phospholipids

a. have hydrophilic tails that face outward and are exposed to water.

b. have hydrophobic heads that face the center of the membrane and are shielded from 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. None of the choices are correct.

Which one of the following substances would have the most trouble crossing a biological membrane by diffusing through the lipid bilayer?

a. CO2

b. O2

c. Na+

d. H2O

c. Na+

The fluid mosaic model describes the plasma membrane as consisting of

a. two layers of phospholipids with protein sandwiched between them.

b. individual proteins and phospholipids that can drift in a phospholipid bilayer.

c. carbohydrates, proteins, and phospholipids that can drift in the membrane.

d. a phospholipid bilayer with embedded carbohydrates.

e. a protein bilayer with embedded phospholipids.

b. individual proteins and phospholipids that can drift in a phospholipid bilayer.

The cholesterol associated with cell membranes

a. makes the cell membrane fluid at room temperature.

b. is an abnormality resulting from a diet high in cholesterol.

c. helps to stabilize the cell membrane at body temperature.

d. is attached to membrane proteins and extends into the watery environment surrounding the cell.

e. None of the choices are correct.

c. helps to stabilize the cell membrane at body temperature.

A major function of glycoproteins and glycolipids in the cell membrane is to

a. help the cell resist swelling.

b. help the cell retain its shape.

c. allow the cells of an embryo to sort themselves into tissues and organs.

d. attach the cell membrane to the cytoskeleton.

e. glue cells together to form tissues.

c. allow the cells of an embryo to sort themselves into tissues and organs.

When physicians perform an organ transplant, they choose a donor whose tissues match those of the recipient as closely as possible. Which of the following cell components are being matched?

a. plasma membrane cholesterols

b. cytoskeletal elements

c. cell-surface carbohydrates

d. plasma membrane proteins

e. plasma membrane phospholipids

c. cell-surface carbohydrates

Most of the functions of a cell membrane are performed by

a. phospholipids.

b. proteins.

c. nucleotides.

d. cholesterol.

e. glycolipids.

b. proteins.

Which one of the following is not a function of membrane proteins? Membrane proteins

a. attach the membrane to the cytoskeleton.

b. serve as enzymes.

c. provide cellular identification tags.

d. form junctions between cells.

e. All of the choices are membrane protein functions.

e. All of the choices are membrane protein functions.

Relaying a message from a membrane receptor to a molecule that performs a specific function within a cell is called

a. self-recognition.

b. competition.

c. signal transduction.

d. inhibition.

e. selective permeability.

c. signal transduction

Which of the following is not a true statement about diffusion? Diffusion

a. occurs when particles spread from areas where they are less concentrated to areas where they are more concentrated.

b. is a result of the kinetic energy of atoms and molecules.

c. requires no input of energy into the system.

d. proceeds until equilibrium is reached.

e. is driven by entropy.

a. occurs when particles spread from areas where they are less concentrated to areas where they are more concentrated

Diffusion does not require the cell to expend ATP. Therefore, diffusion is considered a type of

a. phagocytosis.

b. passive transport.

c. exocytosis.

d. endocytosis.

e. active transport.

b. passive transport.

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 an equal movement in both directions across the membrane.

b. exhibit a net movement to the side with lower water concentration.

c. exhibit a net movement to the side with higher water concentration.

d. not cross the membrane.

e. exhibit a net movement to the side with lower solute concentration.

b. exhibit a net movement to the side with lower water concentration.

In lab, you use a special balloon that is permeable to water but not sucrose to make an "artificial cell." The balloon is filled with a solution of 20% sucrose and 80% water and is immersed in a beaker containing a solution of 40% sucrose and 60% water. Which of the following will occur?

a. None of the choices will occur.

b. Sucrose will enter the balloon.

c. Water will enter the balloon.

d. Sucrose will leave the balloon.

e. Water will leave the balloon.

e. Water will leave the balloon.

In lab, you use a special balloon that is permeable to water but not sucrose to make an "artificial cell." The balloon is filled with a solution of 20% sucrose and 80% water and is immersed in a beaker containing a solution of 40% sucrose and 60% water. The solution in the balloon is __________ relative to the solution in the beaker.

a. hydrophobic

b. isotonic

c. hypertonic

d. hypotonic

e. hydrophilic

d. hypotonic

A cell that neither gains nor loses water when it is immersed in a solution is

a. metabolically inactive.

b. dead.

c. hypertonic to its environment.

d. hypotonic to its environment.

e. isotonic to its environment.

e. isotonic to its environment.

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 hypotonic to the protozoan.

b. is hypertonic to the protozoan.

c. None of the choices are correct.

d. is isotonic to the protozoan.

e. contains a higher concentration of solutes than the protozoan.

a. is hypotonic to the protozoan.

Osmosis can be defined as

a. active transport.

b. endocytosis.

c. the diffusion of nonpolar molecules.

d. the diffusion of water.

e. the diffusion of a solute.

d. the diffusion of water.

If placed in tap water, an animal cell will undergo lysis, whereas a plant cell will not. What accounts for this difference?

a. the relative impermeability of the plant cell membrane to water

b. the fact that plant cells are isotonic to tap water

c. the relative inelasticity and strength of the plant cell wall

d. expulsion of water by the plant cell’s central vacuole

e. the relative impermeability of the plant cell wall to water

c. the relative inelasticity and strength of the plant cell wall

A plant cell in a hypotonic solution

a. is turgid.

b. lyses.

c. shrivels.

d. wilts.

e. is flaccid.

a. is turgid

You are adrift in the Atlantic Ocean, and, being thirsty, drink the surrounding seawater. As a result,

a. your cells lyse, due to the excessive intake of salt.

b. you quench your thirst.

c. None of the choices are correct.

d. you dehydrate yourself.

e. your cells become turgid.

d. you dehydrate yourself.

The organ that plays a major role in osmoregulation in humans is the

a. pancreas.

b. heart.

c. spleen.

d. kidney.

e. gallbladder.

d. kidney.

Facilitated diffusion across a biological membrane requires __________ and moves a substance __________ its concentration gradient.

a. energy . . . down

b. transport proteins . . . against

c. transport proteins . . . down

d. energy and transport proteins . . . against

e. energy and transport proteins . . . down

c. transport proteins . . . down

The molecules responsible for membrane transport are

a. ATP.

b. carbohydrates.

c. proteins.

d. phospholipids.

e. steroids.

c. proteins.

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. None of the choices are correct.

b. facilitated diffusion

c. osmosis

d. active transport

e. diffusion

d. active transport

Which one of the following is a typical feature of an ATP-driven active transport mechanism?

a. The solute must be phosphorylated before it can bind to the transport protein.

b. The transport protein must cross to the correct side of the membrane before the solute can bind to it.

c. None of the choices are correct.

d. The transport protein is irreversibly phosphorylated as transport takes place.

e. The transport protein catalyzes the conversion of ADP to ATP.

c. None of the choices are correct

Active transport

a. requires the cell to expend energy.

b. All of the choices are correct.

c. can move solutes up a concentration gradient.

d. uses ATP as an energy source.

e. can involve the coupled passage of solutes.

b. All of the choices are correct.

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. pinocytosis

b. diffusion

c. exocytosis

d. endocytosis

e. passive transport

c. exocytosis

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 breakdown of ATP is needed for transport to occur.

c. The substance enters the cell when its concentration is higher outside the cell than inside.

d. None of the choices are correct.

e. All of the choices are correct.

b. The breakdown of ATP is needed for transport to occur.

The act of a white blood cell engulfing a bacterium is

a. receptor-mediated endocytosis.

b. pinocytosis.

c. phagocytosis.

d. diffusion.

e. osmosis.

c. phagocytosis.

Phagocytosis is to eating as pinocytosis is to

a. lysis.

b. drinking.

c. chewing.

d. hydrolysis.

e. osmosis.

b. drinking.

Cells acquire LDLs by

a. pinocytosis.

b. receptor-mediated endocytosis.

c. diffusion.

d. phagocytosis.

e. osmosis.

b. receptor-mediated endocytosis.

An inherited lack (or shortage) of functional LDL receptors causes

a. hypercholesterolemia.

b. hyperbilirubinemia.

c. cystic fibrosis.

d. Marfan’s syndrome.

e. type I diabetes.

a. hypercholesterolemia.

The ultimate source of nearly all energy available to life on Earth is

a. sunlight.

b. photosynthesis.

c. cellular respiration.

d. wind.

e. electricity.

a. sunlight.

Ultimately, nearly all animals are dependent on __________ as their source of energy.

a. electricity

b. photosynthesis

c. cellular respiration

d. heat

e. wind

b. photosynthesis

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