Deck 5: The Working Cell

Question 1

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 free water concentration.
B) exhibit a net movement to the side with higher free 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.

Answer 1

A

Question 2

Plasma membranes are selectively permeable. This means that

A) anything can pass into or out of a cell as long as the membrane is intact and the cell is healthy.
B) the plasma membrane allows some substances to enter or leave a cell more easily than others.
C) glucose cannot enter the cell.
D) plasma membranes must be very thick.

Answer 2

B

Question 3

Aspirin and other nonsteroidal anti-inflammatory drugs (NSAID) inhibit inflammation by inhibiting an enzyme in the prostaglandin pathway. However, inhibiting this enzyme also inhibits other pathways that protect the stomach from damage by stomach acid and that form blood clots. What can you conclude from this?

A) The enzyme inhibition is nonreversible.
B) The enzyme is found in many different types of cells.
C) Prostaglandins cause blood clotting.
D) Aspirin should not be given to people who people who need to synthesize enzymes.

Answer 3

B

Question 4

Oxygen crosses a plasma membrane by

A) osmosis.
B) active transport.
C) endocytosis.
D) passive transport.

Question 5

Which of the following statements regarding diffusion is false?

A) Diffusion is a result of the thermal energy of atoms and molecules.
B) Diffusion requires no input of energy into the system.
C) Diffusion occurs when particles spread from areas where they are less concentrated to areas where they are more concentrated.
D) Diffusion occurs even after equilibrium is reached and no net change is apparent.

Question 6

The cholesterol associated with animal cell membranes

A) is attached to membrane proteins and extends into the watery environment surrounding the cell.
B) helps to keep phospholipids from being too close to one another.
C) is an abnormality resulting from a diet high in cholesterol.
D) helps solidify the membranes when the room temperature is below freezing.

Question 7

If you were working for a pharmaceutical company as part of a drug discovery team, which of these enzyme inhibitors would you suggest as a productive avenue for drug development?

A) a drug to treat high blood pressure that reversibly inhibits an enzyme catalyzing production of a chemical that causes blood vessels to contract
B) a drug to treat diabetes that irreversibly inhibits an enzyme in the metabolic pathway to synthesize glucose
C) a compound that acts as a competitive inhibitor for a digestive enzyme produced only in the presence of certain foods
D) a compound that inhibits enzymes by significantly changing the pH throughout the body

Question 8

Most of the functions of a cell membrane, including transport and enzymatic function, are performed by

A) glycolipids.
B) proteins.
C) phospholipids.
D) cholesterol.

Question 9

Osmosis can be defined as

A) the diffusion of water.
B) the diffusion of nonpolar molecules.
C) active transport.
D) the diffusion of a solute.

Question 10

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

A) exocytosis.
B) passive transport.
C) active transport.
D) endocytosis.

Question 11

Which of the following statements regarding membrane protein function is false?

A) Membrane proteins serve as enzymes.
B) Membrane proteins act as receptors to molecules like hormones.
C) Membrane proteins form junctions between cells.
D) Membrane proteins produce phospholipids.

Question 12

Relaying a message from a membrane receptor to a molecule that performs a specific function within a cell occurs when

A) a signaling molecule binds to a protein that extends to the outside of the cell.
B) a protein receptor on the interior of the membrane becomes bound by a signaling molecule.
C) the extracellular matrix is moved to the inside of the cell.
D) glycoproteins are recognized by other cells.

Question 13

Many physiological conditions are related to particular proteins in cell membranes. The number of insulin receptors in membranes is related to the amount of insulin present around those cells. If the presence of increased insulin results in a decrease in receptors and a decrease in insulin results in an increase in insulin receptors, this would be an example of

A) a metabolic pathway.
B) feedback inhibition.
C) passive transport.
D) competitive inhibition.

Question 14

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

A) O2
B) CO2
C) Na+
D) a small, nonpolar molecule such as butane (C4H10)

Question 15

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

Question 16

Which of the following statements regarding membrane function is false?

A) The plasma membrane forms a selective barrier around the cell.
B) The plasma membrane plays a role in transferring signals to the cell's interior.
C) The plasma membrane has receptors for chemical messages.
D) The plasma membrane is the control center of the cell.

Question 17

How do fatty acids travel through a cell membrane?

A) diffusion
B) active transport
C) carrier proteins
D) endocytosis

Question 18

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) are able to drift about in the plasma membrane.
D) remain fluid because they are tightly packed against one another.

Question 19

The fluid mosaic model describes the plasma membrane as consisting of

A) a phospholipid bilayer with embedded carbohydrates.
B) two layers of phospholipids with cholesterol sandwiched between them.
C) carbohydrates and phospholipids that can drift in the membrane.
D) diverse proteins embedded in a phospholipid bilayer.

Question 20

All cells are enclosed by a plasma membrane that is similar in ________ and ________.

A) thickness; composition
B) permeability; content
C) lucidity; texture
D) structure; function

Question 21

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) receptor-mediated endocytosis
B) exocytosis
C) diffusion
D) phagocytosis

Question 22

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) contains a higher concentration of solutes than the protozoan.
D) is hypertonic to the protozoan.

Question 23

Which of the following processes can move a solute against its concentration gradient?

A) osmosis
B) passive transport
C) facilitated diffusion
D) active transport

Question 24

Which of the following statements is true for all types of passive transport?

A) Proteins are needed to transport molecules across the membrane.
B) The concentration gradient is the driving force.
C) Only small polar molecules are able to cross the plasma membrane.
D) Ions never cross the plasma membrane by passive transport.

Question 25

In the 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) isotonic
B) hypotonic
C) hypertonic

Question 26

A cell that has neither a net gain of water nor a net loss of water when it is immersed in a solution must be

A) isotonic to its environment.
B) hypertonic to its environment.
C) hypotonic to its environment.

Question 27

Aquaporins

A) allow water to cross the plasma membrane via facilitated diffusion.
B) allow water to cross the plasma membrane against its concentration gradient.
C) allow for the active transport of water.
D) are found in all cells.

Question 28

Cells acquire low-density lipoproteins (LDLs) by

A) diffusion.
B) receptor-mediated endocytosis.
C) exocytosis.
D) phagocytosis.

Question 29

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

A) you quench your thirst.
B) your cells become turgid.
C) you dehydrate yourself.
D) your cells lyse from excessive water intake.

Question 30

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

A) energy and transport proteins; down
B) transport proteins; down
C) energy and transport proteins; against
D) transport proteins; against

Question 31

White blood cells (WBCs) are more resistant to lysis than red blood cells (RBCs). When looking at a sample of blood for WBCs, what 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 in a hypotonic solution, which will cause the RBCs to lyse.
D) Mix the blood in a hypertonic solution, which will cause the RBCs to lyse.

Question 32

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

A) the expulsion of water by the plant cell's central vacuole
B) the relative impermeability of the plant cell wall to water
C) the fact that plant cells are isotonic to tap water
D) the relative inelasticity and strength of the plant cell wall

Question 33

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 transport protein is irreversibly phosphorylated as transport takes place.
C) The transport protein catalyzes the conversion of ADP to ATP.
D) The solute moves against the concentration gradient.

Question 34

A plant cell in a hypotonic solution

A) becomes turgid because of an inflow of water.
B) bursts because of an inflow of water.
C) shrivels because of an outflow of water.
D) wilts because of an outflow of water.

Question 35

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

Question 36

In a hypotonic solution, an animal cell will

A) lyse.
B) experience turgor.
C) neither gain nor lose water.
D) shrivel.

Question 37

The molecules responsible for membrane transport are

A) steroids.
B) phospholipids.
C) carbohydrates.
D) proteins.

Question 38

In the 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) Water will leave the balloon.
B) Water will enter the balloon.
C) Sucrose will leave the balloon.
D) Sucrose will enter the balloon.

Question 39

The process of a white blood cell engulfing a bacterium is

A) osmosis.
B) receptor-mediated endocytosis.
C) exocytosis.
D) phagocytosis.

Question 40

Which of the following statements regarding active transport is false?

A) Active transport uses ATP as an energy source.
B) Active transport can move a solute against its concentration gradient.
C) Active transport requires the cell to expend energy.
D) Active transport is driven by the concentration gradient.

Question 41

Which of the following processes is classified as a metabolic pathway?

A) the synthesis of a protein
B) water moving across a membrane via osmosis
C) the death and lysis of a cell
D) the movement of oxygen across a membrane

Question 42

Which of the following statements regarding enzymes is true?

A) Enzymes are inorganic.
B) An enzyme's function is unaffected by changes in pH.
C) Enzymes catalyze specific reactions.
D) All enzymes depend on protein cofactors to function.

Question 43

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

A) carboxylation.
B) ionization.
C) phosphorylation.
D) hydrogenation.

Question 44

When an enzyme catalyzes a reaction

A) it lowers the activation energy of the reaction.
B) it raises the activation energy of the reaction.
C) it acts as a reactant.
D) it is used once and discarded.

Question 45

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) ATP is a disposable form of chemical energy, used once and then discarded by the cell.

Question 46

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

A) chemical energy into kinetic energy.
B) chemical energy into potential energy.
C) kinetic energy into potential energy.
D) kinetic energy into thermal energy.

Question 47

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) A single cell or the planet Earth could be a thermodynamic system.
C) An open system exchanges both energy and matter with its surroundings.
D) An automobile engine is a closed system because it does not exchange energy and matter with its surroundings.

Question 48

Most of a cell's enzymes are

A) lipids.
B) proteins.
C) amino acids.
D) carbohydrates.

Question 49

Which of the following statements regarding enzyme function is false?

A) An enzyme's function depends on its three-dimensional shape.
B) Enzymes are very specific for certain substrates.
C) Enzymes are used up when they catalyze a chemical reaction so must be synthesized for each new chemical reaction.
D) Enzymes emerge unchanged from the reactions they catalyze.

Question 50

Anything that prevents ATP formation will most likely

A) result in cell death.
B) force the cell to rely on lipids for energy.
C) force the cell to rely on ADP for energy.
D) have no effect on the cell.

Question 51

In the reaction A → B + C + heat

A) there is a net input of energy.
B) the potential energy of the products is greater than that of the reactant.
C) the potential energy of the products is less than that of the reactant.
D) entropy has decreased.

Question 52

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.

Question 53

Which of the following statements about ATP is true?

A) It contains five phosphate groups.
B) Extremely stable bonds link the second and third phosphate groups.
C) It contains the sugar glucose.
D) It releases energy when one phosphate group leaves ATP.

Question 54

What is the basic difference between exergonic and endergonic reactions?

A) Exergonic reactions involve ionic bonds; endergonic reactions involve covalent bonds.
B) Exergonic reactions involve the breaking of bonds; endergonic reactions involve the formation of bonds.
C) Exergonic reactions release energy; endergonic reactions absorb it.
D) In exergonic reactions, the reactants have less chemical energy than the products; in endergonic reactions, the opposite is true.

Question 55

Which of the following processes is endergonic?

A) the burning of wood
B) the synthesis of glucose from carbon dioxide and water
C) the breakdown of glucose
D) cellular respiration

Question 56

An energy barrier

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

Question 57

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.

Question 58

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.

Question 59

Which of the following direct energy transfers is impossible in living systems?

A) light energy to chemical energy
B) chemical energy to kinetic energy
C) light energy to potential energy
D) heat to light energy

Question 60

When a cell uses chemical energy to perform work, it uses the energy released from a(n) ________ reaction to drive a(n) ________ reaction.

A) exergonic; endergonic
B) endergonic; exergonic
C) exergonic; spontaneous
D) spontaneous; exergonic

Question 61

After reading the paragraph below, answer the questions that follow.
Water movement is important in urine formation in the kidneys. Urine is formed when the blood is filtered by the kidneys into kidney tubules. Three figures are presented here that relate to how the kidney tubules respond to the administration of the hormone vasopressin. The direction that water flows in these figures is from the kidney tubules back into the blood.
Figure A. Changes in permeability of tubules in the kidney in response to the hormone vasopressin (AVP), which aids in osmoregulation.
Figure B. Density of aquaporins in kidney tubule cells before, during, and after administration of vasopressin.
Figure C. Permeability of tissues to water before, during, and after administration of vasopressin.
How do the data in Figure A relate to the data in Figures B and C?

A) Figure B shows the method used to obtain the data in Figure A.
B) Figure C is essentially a summary of the data in Figure A.
C) Figure A is about water movement, and Figures B and C are about presence of aquaporins.
D) Figure A has data for more than 2 hours, and Figures B and C show data all collected at the same time.

Question 62

Heating inactivates enzymes by

A) breaking the covalent bonds that hold the molecule together.
B) removing phosphate groups from the enzyme.
C) causing enzyme molecules to stick together.
D) changing the enzyme's three-dimensional shape.

Question 63

After reading the paragraph below, answer the questions that follow.
Water movement is important in urine formation in the kidneys. Urine is formed when the blood is filtered by the kidneys into kidney tubules. Three figures are presented here that relate to how the kidney tubules respond to the administration of the hormone vasopressin. The direction that water flows in these figures is from the kidney tubules back into the blood.
Figure A. Changes in permeability of tubules in the kidney in response to the hormone vasopressin (AVP), which aids in osmoregulation.
Figure B. Density of aquaporins in kidney tubule cells before, during, and after administration of vasopressin.
Figure C. Permeability of tissues to water before, during, and after administration of vasopressin.
Using the data from the graphs and what you know about membranes and metabolic pathways, predict which of the following is the likely reason why actions of aquaporins in a membrane can change so rapidly.

A) The number of aquaporins in the membrane is constant, but the pores have to be activated.
B) Aquaporins are inserted into the membrane as needed.
C) Aquaporins are only in cells that need to be permeable to water.
D) Aquaporins use ATP to pump water across the membrane, and their action is limited by the metabolic pathways that produce ATP.

Question 64

After reading the paragraphs below, answer the questions that follow.
Americans spend up to $100 billion annually for bottled water (41 billion gallons). The only beverages with higher sales are carbonated soft drinks. Recent news stories have highlighted the fact that most bottled water comes from municipal water supplies (the same source as your tap water), although it may undergo an extra purification step called reverse osmosis.
Imagine two tanks that are separated by a membrane that is permeable to water, but not to the dissolved minerals present in the water. Tank A contains tap water and tank B contains the purified water. In the reverse osmosis process, pressure is applied to the tap water tank to force the water molecules across the membrane into the pure water tank.
After the reverse osmosis system has been operating for 30 minutes, the solution in tank A would

A) be hypotonic to tank B.
B) be isotonic to tank B.
C) be hypertonic to tank B.

Question 65

After reading the paragraph below, answer the questions that follow.
Water movement is important in urine formation in the kidneys. Urine is formed when the blood is filtered by the kidneys into kidney tubules. Three figures are presented here that relate to how the kidney tubules respond to the administration of the hormone vasopressin. The direction that water flows in these figures is from the kidney tubules back into the blood.
Figure A. Changes in permeability of tubules in the kidney in response to the hormone vasopressin (AVP), which aids in osmoregulation.
Figure B. Density of aquaporins in kidney tubule cells before, during, and after administration of vasopressin.
Figure C. Permeability of tissues to water before, during, and after administration of vasopressin.
Based on the data from these figures, what do you expect the urine of a person to be like when vasopressin is having an effect on the kidney tubules?

A) The urine will be salty.
B) The urine will be dilute.
C) The urine will be concentrated.
D) There will be large volumes of urine.

Question 66

Which part of the ATP molecule breaks free of the rest when an ATP molecule releases energy?

A) part A
B) part B
C) part C
D) part D

Question 67

Which of the following is a coenzyme?

A) zinc
B) vitamin B6
C) iron
D) iodine

Question 68

After reading the paragraph below, answer the questions that follow.
Lipase is an enzyme released by the pancreas that digests fats in the small intestine; however, lipase is also found in bacteria. Researchers examined lipase function in two species of bacteria, species X and species Y. Data regarding the activity of lipase as a function of temperature are shown below for the lipase from bacteria X (white circles) and the lipase from bacteria Y (black circles). Use this information to answer the following three questions.
Lipase activity as a function of temperature.
What is true regarding the function of lipase?

A) Lipase raises the activation energy required to hydrolyze proteins.
B) Lipase lowers the activation energy required to hydrolyze proteins.
C) Lipase raises the activation energy required to hydrolyze fats.
D) Lipase lowers the activation energy required to hydrolyze fats.

Question 69

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

A) Elevated body temperature will increase reaction rates in the child's cells and overload the limited number of enzymes found in the cell.
B) Elevated body temperatures may denature enzymes. This would interfere with the cell's abilities to catalyze various reactions.
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 cause molecules to vibrate more quickly and prevent enzymes from easily attaching to reactants. This would slow vital body reactions.

Question 70

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.

Question 71

Which figure depicts an animal cell placed in a solution hypotonic to the cell?

A) cell A
B) cell B
C) cell C
D) cell D

Question 72

A man with a dirty cut on his hand appears at the emergency department for treatment. In order to clean the wound, the health-care provider should use

A) a solution of very low pH.
B) a solution of sterilized tap water.
C) a weak (low concentration) solution of salt water.
D) distilled water.

Question 73

Suppose that while the reverse osmosis system is running tank B becomes contaminated with salt water such that it ends up with a higher salt concentration than tank A. What would happen if the reverse osmosis system was turned off?

A) There would be a net flow of water from tank A to tank B.
B) There would be a net flow of water from tank B to tank A.
C) Water would flow in equal amounts in both directions.

Question 74

Which of the following substances could be a cofactor?

A) a protein
B) a polypeptide
C) a zinc atom
D) a ribosome

Question 75

A group of single-cell organisms collected from the ocean was brought into the lab for examination. The lab assistant was concerned that the water had become full of toxic waste products and so added clean water to the culture. All of the organisms died, and when she looked at them under the microscope, all she could see were bits and pieces of them scattered throughout the water. What likely happened?

A) She added water that was hypotonic to the culture of organisms, and they ruptured.
B) She added seawater to which she had added too much salt, and they ruptured.
C) She added water isotonic to the organisms, causing too much water to move in and out of the organisms, and they ruptured.
D) She added too little salt to the seawater she added, and the organisms all lost too much water and shriveled up.

Question 76

Inhibition of an enzyme is irreversible when

A) a competitive inhibitor is involved.
B) a noncompetitive inhibitor is involved.
C) there is an abundance of substrate.
D) covalent bonds form between inhibitor and enzyme.

Question 77

If you shut off the system and pressure was no longer applied to tank A, you would expect the

A) net flow of water to be from tank A to tank B.
B) water to reverse net flow from tank B to tank A.
C) water to flow in equal amounts in both directions.

Question 78

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) irreversible inhibition.

Question 79

What is true about the data in the accompanying figure?

A) The solid line represents a reaction that has been catalyzed by an enzyme.
B) The dashed line represents a reaction that includes an enzyme and a cofactor.
C) Both lines represent endergonic reactions.
D) The energy of the products is higher than the energy of the reactants.

Question 80

Water that is filtered out of the blood by the kidneys is returned to the body through the action of aquaporins. Which of the following statements about water balance disorders is scientifically accurate?

A) People with heart failure often swell due to too much water from excess numbers of aquaporins.
B) Water retention (too much water) in pregnancy can be due to a decreased number of aquaporins.
C) Kidney failure and decreased urine production are due to increased numbers of aquaporins.
D) Small amounts of urine are produced by people who inherit a defect in the ability to make aquaporins.