Chapter 5: The Working Cell

D) Isotonic to its environment.

A cell that has neither a net gain of water nor net loss of water when it is immersed in a solution must be... A) Hypertonic to its environment. B) Hypotonic to its environment. C) Metabolically inactive. D) Isotonic to its environment.

Active site

A substrate fits into a region of the enzyme called the ______.

Endergonic

An ______ reaction requires an input of energy and yields products rich in potential energy.

C) Prevents the spontaneous breakdown of molecules in the cell.

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

A) Antibiotics inhibit enzymes that are essential to the survival of bacteria only.

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

A) Competitive inhibition

Azidothymidine (AZT) is an antiretroviral drug used in the treatment of HIV. It shares a structural similarity to a nucleotide. What might be the mode of action for this drug? A) Competitive inhibition B) Feedback inhibition C) Noncompetitive inhibition D) Mixed inhibition

Passive transport

Diffusion across a cell membrane does not require energy, so it is called ______.

D) Passive transport.

Diffusion does not require the cell to expend ATP. Therefore, diffusion is considered a type of A) Endocytosis. B) Active transport. C) Exocytosis. D) Passive transport.

Kinetic

Light is also a type of ______energy; it can be harnessed to power photosynthesis.

A) Microbes are engulfed into the macrophage via phagocytosis.

Macrophages are white blood cells that roam the body searching for invading microbes. Inside macrophage vacuoles these invaders are destroyed. How do the microbes get inside the macrophages? A) Microbes are engulfed into the macrophage via phagocytosis. B) The invaders cross the membranes via active transport through specific transport proteins. C) The invaders cross the membranes via facilitated transport through specific transport proteins. D) They are taken in by the form of exocytosis known as pinocytosis.

A) Increases the rate of LDL receptor-mediated endocytosis

New drugs are being developed to lower levels of circulating cholesterol. A successful drug would be one that _____. A) Increases the rate of LDL receptor-mediated endocytosis B) Binds to the LDL receptor and blocks receptor-mediated endocytosis C) Blocks the synthesis of LDL receptors D) Increases exocytosis in cells that line blood vessels, especially those of the heart

D) Easily pass through a membrane's lipid bilayer.

Small, nonpolar, hydrophobic molecules such as fatty acids... A) Very slowly diffuse through a membrane's lipid bilayer. B) Require transport proteins to pass through a membrane's lipid bilayer. C) Are actively transported across cell membranes. D) Easily pass through a membrane's lipid bilayer.

Phagocytosis, Pinocytosis and Receptor-mediated

Th types of endocytosis are ______ , ______ and ______.

D) The region of an enzyme that attaches to a substrate.

The active site of an enzyme is... A) The highly changeable portion of an enzyme that adapts to fit the substrates of various reactions. B) The region of a product that detaches from the enzyme. C) The region of a substrate that is changed by an enzyme. D) The region of an enzyme that attaches to a substrate.

C) Helps to keep phospholipids from being too close to one another.

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

D) Phagocytosis.

The process of a white blood cell engulfing a bacterium is... A) Osmosis. B) Pinocytosis. C) Receptor-mediated endocytosis. D) Phagocytosis.

C) Noncompetitive inhibitor

The synthesis of an amino acid follows this pathway: precursor A → intermediate B → amino acid C. Each reaction is catalyzed by a different enzyme. This metabolic pathway is controlled by feedback inhibition with amino acid C inhibiting the conversion of precursor A to intermediate B. Amino acid C acts as a _____ of the first enzyme in the pathway. A) Catalyst B) Substrate C) Noncompetitive inhibitor D) Competitive inhibitor

A) The direction of the oxygen concentration gradient

What controls the direction of a molecule, such as oxygen, involved in passive transport? A) The direction of the oxygen concentration gradient B) The size of the oxygen molecule C) The amount of energy available to transport oxygen D) The type of cell to or from which the oxygen molecule is moving

Exocytosis

______ is used to export bulky molecules, such as proteins or polysaccharides.

Endocytosis

______ is used to take in large molecules.

Exergonic

______ reactions release energy.

B) Arrangement of atoms within molecules

Cells store energy that they use for work in the _____. A) Thermal energy of molecules B) Arrangement of atoms within molecules C) Oxygen cells take in D) Water that is moved inside the cell

Substrate

The specific reactant that an enzyme acts on is called the enzyme's ______.

Pinocytosis

What is defined as cellular drinking?

Phagocytosis

What is defined as cellular eating?

A) Membrane proteins transfer genetic information to the cytoplasm.

Which of the following statements regarding membrane protein function is false? A) Membrane proteins transfer genetic information to the cytoplasm. B) Membrane proteins serve as enzymes. C) Membrane proteins act as receptors to molecules like hormones. D) Membrane proteins form junctions between cells.

B) Zinc atom

Which of the following substances could be a cofactor? A) Polypeptide B) Zinc atom C) Protein D) Ribosome

Isotonic

In a(n) ______ solution, the concentration of solute is the same on both sides of a membrane, and the cell volume will not change.

Enzymes

What increases the rate of a reaction without being consumed by the reaction.

Endergonic

What type of reaction is this?

B) Excessive salt ions can cause an enzyme to denature.

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

A) Remain standing upright

When placed in a hypotonic environment, where the solute concentration is below that of the cell, a houseplant will _____. A) Remain standing upright B) Go limp and lifeless C) Go brown at the edges of its leaves D) Die

A) Active transport

Which of the following processes can move a solute against its concentration gradient? A) Active transport B) Facilitated diffusion C) Passive transport D) Osmosis

A) Nine

You're on the pilot episode of a new reality show called "The Transport Factor." The host hands you three different amino acids, four different sugars, and two different ions. Then the host shouts, "How many different proteins does the cell need to move these molecules across the plasma membrane using facilitated transport?" Quickly, you correctly respond: _____. A) Nine B) Five C) Three D) One

B) Kinetic ... chemical

Light is _____ energy, which is converted by plants into molecules, which possess _____ energy. A) Chemical ... potential B) Kinetic ... chemical C) Potential ... kinetic D) Chemical ... kinetic

A) The diffusion of water.

Osmosis can be defined as... A) The diffusion of water. B) The diffusion of nonpolar molecules. C) The diffusion of a solute. D) Active transport.

A) Understanding the enzyme's structure would help pharmaceutical companies design molecules that fit to the binding site and alter activity.

A pharmaceutical company wishes to focus on an enzyme to develop new medications. What type of study would be of the greatest benefit? A) Understanding the enzyme's structure would help pharmaceutical companies design molecules that fit to the binding site and alter activity. B) Studying the structure of an enzyme would help pharmaceutical companies determine the enzyme's substrate. C) Knowing the structure of enzymes may make it possible to design enzymes that raise the activation energy above that of the spontaneous reaction to allow more efficient drug synthesis. D) Studying the structure would help pharmaceutical companies create enzymes that are not destroyed during reactions.

A) Transport proteins; down

Facilitated diffusion across a biological membrane requires ________ and moves a substance ________ its concentration gradient. A) Transport proteins; down B) Energy and transport proteins; down C) Transport proteins; against D) Energy and transport proteins; against

C) Each person has a unique set of carbohydrate chains attached to his or her plasma membranes.

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

Active

In ______ transport, a cell must expend energy to move a solute against its concentration gradient.

D) Increase the negative charge of each phosphate group.

In a theoretical world where all things are possible, how could you increase the amount of energy that could be stored in a molecule of ATP? A) Alter the first and third groups to make them positive. B) Convert the negative charge of the phosphate groups to a positive charge. C) Change the middle phosphate group from a negative to a positive charge. D) Increase the negative charge of each phosphate group.

Hypertonic

In a(n) ______ solution, the solute concentration is higher outside the cell, water molecules move out of the cell, and the cell will shrink.

Hypotonic

In a(n) ______ solution, the solute concentration is lower outside the cell, water molecules move into the cell, and the cell will expand and may burst.

D) Would stay together but in a reverse orientation, with their tails projecting outward

In an oil-based, nonpolar environment, phospholipids would arrange themselves so that they __________. A) Would pack more tightly together than they would in a watery environment B) Would never associate but instead would remain as individual molecules completely dissolved in the oil C) Would not pack together at all D) Would stay together but in a reverse orientation, with their tails projecting outward

C) Cells couple energy-releasing reactions to energy-requiring reactions.

In plant cells, carbon dioxide and water are joined to form carbohydrates. Plant cells can also break down carbohydrates such as glucose, releasing carbon dioxide, water, and energy. No one has ever observed such reactions between water and carbon dioxide outside of living cells. What allows simple molecules to assemble into more complex molecules, and also disassemble, in cells but not in other, nonbiological environments? A) Cells are subject to only the first law, not the second law, of thermodynamics. B) Cells possess properties not seen in nonliving things, which allow them to run physical processes in reverse. C) Cells couple energy-releasing reactions to energy-requiring reactions. D) Cells are far more efficient in energy transactions than are nonliving substances.

B) Kinetic energy is the energy of a moving object, whereas chemical energy is the potential energy of molecules.

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 is the energy of a moving object, whereas chemical energy is the potential energy of molecules. C) Kinetic energy can be converted into various forms of energy, whereas chemical energy can only be converted into heat. D) Chemical energy is a particular form of kinetic energy.

B) The difference in water concentration across a selectively permeable membrane

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

B) Proteins

Overall, membranes seem to have a great deal in common, but on closer inspection it is revealed that membranes of different cells have unique properties. What is the primary component of membranes that gives membranes cell-specific properties? A) Cholesterol B) Proteins C) Cytoskeleton D) Phospholipids

A) The plasma membrane allows some substances to enter or leave a cell more easily than others.

Plasma membranes are selectively permeable. This means that... A) The plasma membrane allows some substances to enter or leave a cell more easily than others. B) Plasma membranes must be very thick. C) Anything can pass into or out of a cell as long as the membrane is intact and the cell is healthy. D) Glucose cannot enter the cell.

C) The sucrase-catalyzed reaction releases the same amount of energy as the spontaneous reaction.

Table sugar, or sucrose, is quite stable, and left on its own at room or even human body temperature, breakdown occurs very slowly. The breakdown of sucrose into the simple sugars fructose and glucose is an exergonic reaction. Sucrase, an enzyme, can increase the reaction rate at least one-million-fold. How does the net amount of energy released during the breakdown of sucrose compare between a spontaneous reaction and one catalyzed by sucrase? A) The sucrase-catalyzed reaction releases roughly two to three times more energy than the spontaneous reaction. B) The sucrase-catalyzed reaction releases one million times more energy than the spontaneous reaction. C) The sucrase-catalyzed reaction releases the same amount of energy as the spontaneous reaction. D) The sucrase-catalyzed reaction releases about one-millionth the energy of the spontaneous reaction.

Osmosis

The diffusion of water across a selectively permeable membrane is called ______.

B) The different membrane-enclosed spaces allow different parts of the cell to perform specific functions.

The eukaryotic cell has multiple membrane-enclosed compartments. This evolutionary innovation provides what advantage to the cell? A) The membrane-enclosed spaces allow for eukaryotic cells to be larger. B) The different membrane-enclosed spaces allow different parts of the cell to perform specific functions. C) The membrane-enclosed spaces have allowed eukaryotes to evolve forms of metabolism that no longer require the intake of any molecules from outside the cell. D) The membrane-enclosed spaces lead to the evolution of many different cell types when they are extruded to form daughter cells with novel functions

B) The activation energy required to initiate this reaction is seldom reached.

The hydrolysis of DNA into nucleotides constitutes an exergonic reaction. Yet, DNA is quite stable. Why is this the case? A) No enzymes exist to facilitate DNA hydrolysis. B) The activation energy required to initiate this reaction is seldom reached. C) Only endergonic reactions proceed rapidly. D) DNA synthesis occurs at the same rate as DNA hydrolysis, so DNA only appears stable.

Aquaporin

The very rapid diffusion of water into and out of certain cells is made possible by a protein channel called an ______.

A) Actively pump water back out of their cells to counter its inflow due to osmosis

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

D) The energy contributes to the entropy of the system.

What happens to the chemical energy that is extracted from molecules by cellular activities but that is not used for cellular work? A) It is used by plant cells for photosynthesis. B) The energy is recycled by the cell. C) The energy is captured by other cells. D) The energy contributes to the entropy of the system.

Diffusion

What is the tendency of particles to spread out evenly in an available space?

C) Water

What substance is transported by aquaporins? A) Urine B) Proteins C) Water D) Salt

Competitive

What type of inhibitor is shown here?

Non-competitive

What type of inhibitor is shown here?

Exergonic

What type of reaction is this?

D) It lowers the activation energy of the reaction.

When an enzyme catalyzes a reaction... A) It is used once and discarded. B) It acts as a reactant. C) It raises the activation energy of the reaction. D) It lowers the activation energy of the reaction.

A) Exhibit a net movement to the side with lower free water concentration.

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.

B) Active transport moves solutes against their concentration gradient; facilitated diffusion moves substances down their concentration gradient.

Which of the following is an accurate comparison of active transport and facilitated diffusion? A) In both types of movement, phosphate groups alter the shape of transport proteins. B) Active transport moves solutes against their concentration gradient; facilitated diffusion moves substances down their concentration gradient. C) Facilitated diffusion requires the use of ATP; active transport does not require ATP. D) Active transport requires membrane proteins; facilitated diffusion does not require membrane proteins.

C) The synthesis of glucose from carbon dioxide and water

Which of the following processes is endergonic? A) Cellular respiration B) The breakdown of glucose C) The synthesis of glucose from carbon dioxide and water D) The burning of wood

C) The concentration gradient is the driving force.

Which of the following statements is true for all types of passive transport? A) Only small polar molecules are able to cross the plasma membrane. B) Ions never cross the plasma membrane by passive transport. C) The concentration gradient is the driving force. D) Proteins are needed to transport molecules across the membrane.

Entropy

______ is the measure of disorder or randomness.