Biology 101 Human Biology Chapter 5

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.

33) Aquaporins

A) allow water to cross the plasma membrane via facilitated diffusion.

A plant cell in a hypotonic solution

A) 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

A) chemical energy into kinetic energy.

Small, nonpolar, hydrophobic molecules such as fatty acids

A) easily pass through a membrane's lipid bilayer.

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

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.

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

A) in membranes.

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

A) isotonic to its environment.

60) When an enzyme catalyzes a reaction,

A) it lowers the activation energy of the reaction.

In a hypotonic solution, an animal cell will

A) lyse.

51) Which of the following examples is classified as a metabolic pathway?

A) protein synthesis

Anything that prevents ATP formation will most likely

A) result in cell death

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

A) signal transduction

Osmosis can be defined as

A) the diffusion of water.

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?

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

Which of the following statements is true among 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.

B) The concentration gradient is the driving force.

Which of the following substances could be a cofactor?

B) a polypeptide

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

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

Phagocytosis is to eating as pinocytosis is to

B) drinking

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?

B) exocytosis

The cholesterol associated with animal cell membranes

B) helps to stabilize the cell membrane at body temperature.

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.

B) hypotonic

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

B) is hypotonic to the protozoan.

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

B) passive transport.

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

B) proteins

Most of a cell's enzymes are

B) proteins.

Cells acquire LDLs by

B) receptor-mediated endocytosis.

Which characteristic promoted the utilization of lipids as the first cell membrane?

B) self-assembly into a simple membrane

45) According to ________, energy cannot be created or destroyed.

B) the first law of thermodynamics

Plasma membranes are selectively permeable. This means that

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

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

B) the second law of thermodynamics.

Which of the following processes is endergonic?

B) the synthesis of glucose from carbon dioxide and water

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

B) transport proteins . . . down

Which of the following is a coenzyme?

B) vitamin B6

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

C) Na+

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.

C) Diffusion occurs when particles spread from areas where they are less concentrated

63) 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.

C) 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? 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.

C) Enzymes catalyze specific reactions.

What is the basic difference between exergonic and endergonic reactions?

C) Exergonic reactions release energy; endergonic reactions absorb it

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?

C) Mix the blood in a hypotonic solution, which will cause the RBCs to lyse.

Membrane phospholipids

C) are able to drift about in the plasma membrane

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?

C) cell-surface carbohydrates

Living systems

C) decrease their entropy while increasing the entropy of the universe.

ATP can be used as the cell's energy exchange mechanism because

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

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

C) feedback inhibition.

Kinetic energy differs from chemical energy in that

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

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

C) phosphorylation.

An energy barrier

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

In the reaction A → B + C + heat,

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

The active site of an enzyme is

C) the region of an enzyme that attaches to a substrate.

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

C) you dehydrate yourself.

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.

D) Active transport is driven by the concentration gradient.

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.

D) An automobile engine is a closed system because it does not exchange energy and matter with its surroundings.

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

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

Which of the following statements about the ATP molecule 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.

D) It releases energy when one phosphate group leaves ATP.

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 transfer genetic information to the cytoplasm.

D) Membrane proteins transfer genetic information to the cytoplasm.

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 signal transduction. C) The plasma membrane has receptors for chemical messages. D) The plasma membrane is the control center of the cell.

D) The plasma membrane is the control center of the cell.

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

D) The solute moves against the concentration gradient.

Substrates bind to an enzyme's ________ site.

D) active

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

D) active transport

Heating inactivates enzymes by

D) changing the enzyme's three-dimensional shape.

Inhibition of an enzyme is irreversible when

D) covalent bonds form between inhibitor and enzyme.

The fluid mosaic model describes the plasma membrane as consisting of

D) diverse proteins embedded in a phospholipid bilayer.

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

D) heat to light energy

Oxygen crosses a plasma membrane by

D) passive transport.

The process of a white blood cell engulfing a bacterium is

D) phagocytosis.

The molecules responsible for membrane transport are

D) proteins.

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

D) structure . . . function

The energy required to initiate an exergonic reaction is called

D) the activation energy.

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

D) the relative inelasticity and strength of the plant cell wall