Bio 101 Ch.5 Quiz

Heating inactivates enzymes by - removing phosphate groups from the enzyme. - breaking the covalent bonds that hold the molecule together. - changing the enzyme's three-dimensional shape. - causing enzyme molecules to stick together.

- changing the enzyme's three-dimensional shape.

Inhibition of an enzyme is irreversible when: - the shape of the enzyme is changed. - a noncompetitive inhibitor is involved. -covalent bonds form between inhibitor and enzyme. - a competitive inhibitor is involved.

-covalent bonds form between inhibitor and enzyme.

Which of the following statements regarding diffusion is false? Diffusion occurs when particles spread from areas where they are less concentrated to areas where they are more concentrated. Diffusion is a result of the thermal energy of atoms and molecules. Diffusion requires no input of energy into the system. Diffusion occurs even after equilibrium is reached and no net change is apparent.

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

Which of the following statements regarding enzyme function is false? Enzymes are used up when they catalyze a chemical reaction, so must be synthesized for each new chemical reaction. An enzyme's function depends on its three-dimensional shape. Enzymes are very specific for certain substrates. Enzymes emerge unchanged from the reactions they catalyze.

Enzymes are used up when they catalyze a chemical reaction, so must be synthesized for each new chemical reaction.

Which of the following statements regarding enzymes is true? All enzymes depend on protein cofactors to function. Enzymes are inorganic. An enzyme's function is unaffected by changes in pH. Enzymes catalyze specific reactions.

Enzymes catalyze specific reactions.

What is the basic difference between exergonic and endergonic reactions? Exergonic reactions release energy; endergonic reactions absorb it. In exergonic reactions, the reactants have less chemical energy than the products; in endergonic reactions, the opposite is true. Exergonic reactions involve the breaking of bonds; endergonic reactions involve the formation of bonds. Exergonic reactions involve ionic bonds; endergonic reactions involve covalent bonds.

Exergonic reactions release energy; endergonic reactions absorb it.

Which of the following statements about the ATP molecule is true? It contains five phosphate groups. It releases energy when one phosphate group leaves ATP. It contains the sugar glucose. Extremely stable bonds link the second and third phosphate groups.

It releases energy when one phosphate group leaves ATP.

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

Na+

The energy required to initiate an exergonic reaction is called the activation energy. exergonic energy. endergonic energy. input energy.

The activation energy

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

The concentration gradient is the driving force.

Which of the following statements regarding membrane function is false? The plasma membrane plays a role in signal transduction. The plasma membrane is the control center of the cell. The plasma membrane has receptors for chemical messages. The plasma membrane forms a selective barrier around the cell.

The plasma membrane is the control center of the cell.

Substrates bind to an enzyme's ________ site. phosphate active allosteric inhibitory

active

Which of the following processes can move a solute against its concentration gradient? facilitated diffusion active transport passive transport osmosis

active transport

Membrane phospholipids have hydrophilic tails that face outward and are exposed to water. remain fluid because they are tightly packed against one another. are able to drift about in the plasma membrane have hydrophobic heads that face the center of the membrane and are shielded from water.

are able to drift about in the plasma membrane

A plant cell in a hypotonic solution wilts because of an outflow of water. becomes turgid because of an inflow of water. shrivels because of an outflow of water. bursts because of an inflow of water.

becomes turgid because of an inflow of water.

Glucose molecules provide energy to power the swimming motion of sperm. In this example, the sperm are changing kinetic energy into potential energy. chemical energy into kinetic energy. kinetic energy into thermal energy. chemical energy into potential energy.

chemical energy into kinetic energy.

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

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

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

exergonic . . . endergonic

Which of the following energy transfers is impossible in living systems? light energy to chemical energy chemical energy to kinetic energy heat to light energy light energy to potential energy

heat to light energy

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. hypotonic hypertonic isotonic hydrophilic

hypotonic

A cell that neither gains nor loses water when it is immersed in a solution must be hypotonic to its environment. isotonic to its environment. hypertonic to its environment. metabolically inactive.

isotonic to its environment.

When an enzyme catalyzes a reaction, it raises the activation energy of the reaction. it lowers the activation energy of the reaction. it acts as a reactant. it is used once and discarded.

it lowers the activation energy of the reaction.

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

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

In a hypotonic solution, an animal cell will lyse. neither gain nor lose water. shrivel. experience turgor.

lyse

Diffusion does not require the cell to expend ATP. Therefore, diffusion is considered a type of endocytosis. exocytosis. active transport. passive transport.

passive transport

Oxygen crosses a plasma membrane by passive transport. osmosis. pinocytosis. active transport.

passive transport

The transfer of a phosphate group to a molecule or compound is called ionization. phosphorylation. hydrogenation. carboxylation.

phosphorylation.

Most of a cell's enzymes are lipids. carbohydrates. amino acids. proteins.

protiens

Which characteristic promoted the utilization of lipids as the first cell membrane? ability to form an impermeable membrane self-assembly into a simple membrane spontaneous degradation of the intracellular environment formation of a semi-solid membrane

self-assembly into a simple membrane

All cells are enclosed by a plasma membrane that is similar in ________ and ________. structure . . . function lucidity . . . texture thickness . . . composition permeability . . . content

structure . . . function

Osmosis can be defined as the diffusion of nonpolar molecules. the diffusion of a solute. the diffusion of water. active transport.

the diffusion of water.

According to ________, energy cannot be created or destroyed. the first law of thermodynamics Aristotle's first principle the third law of thermodynamics the second law of thermodynamics

the first law of thermodynamics

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

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

In the reaction A → B + C + heat, the potential energy of the products is greater than that of the reactant. entropy has decreased. the potential energy of the products is less than that of the reactant. there is a net input of energy.

the potential energy of the products is less than that of the reactant.

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

the region of an enzyme that attaches to a substrate.

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

the relative inelasticity and strength of the plant cell wall

Which of the following processes is endergonic? the breakdown of glucose the burning of wood the synthesis of glucose from carbon dioxide and water cellular respiration

the synthesis of glucose from carbon dioxide and water

Facilitated diffusion across a biological membrane requires ________ and moves a substance ________ its concentration gradient. energy and transport proteins . . . down transport proteins . . . against transport proteins . . . down energy and transport proteins . . . against

transport proteins . . . down

Which of the following statements regarding active transport is false? Active transport is driven by the concentration gradient. Active transport uses ATP as an energy source. Active transport requires the cell to expend energy. Active transport can move a solute against its concentration gradient.

Active transport is driven by the concentration gradient.