Chapter 5 (Mastering Biology)

Aquaporins

Allow water to cross the plasma membrane via facilitated diffusion.

Antibiotics - for example, penicillin - cannot be used to treat viral infections, such as the common cold. Why?

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

Frequently, transplanted organs are rejected by the recipient's body. How is this reaction related to plasma membranes?

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

What is the basic difference between exergonic and endergonic reactions?

Exergonic reactions release energy; endergonic reactions absorb it.

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

Osomosis

The plasma membrane is selectively permeable. Which of the following can pass freely through the membrane with no assistance?

Oxygen and carbon dioxide

What substance is transported by aquaporins?

Water

Which of the following is a difference between active transport and facilitated diffusion? a. Facilitated diffusion involves transport proteins, and active transport does not. b. Active transport requires the expenditure of cellular energy, and facilitated diffusion does not. c. Active transport involves transport proteins, and facilitated diffusion does not. d. Facilitated diffusion can move solutes against a concentration gradient, and active transport cannot.

b. Active transport requires the expenditure of cellular energy, and facilitated diffusion does not.

New drugs are being developed to lower levels of circulating cholesterol. A successful drug would be one that _____.

increases the rate of LDL receptor-mediated endocytosis

The mechanism of enzyme action is to _____.

lower the energy of the activation of a reaction

The first law of thermodynamics _____.

states that energy is neither created nor destroyed

The energy required to initiate an exergonic reaction is called

Activation energy

Cells store energy that they use for work in the _____.

Arrangement of atoms within molecules.

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

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

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?

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

When placed in a hypotonic environment, where the solute concentration is below that of the cell, a houseplant will _____.

Remain standing upright

Which of the following statements is true about passive transport? a. Passive transport phenomena can never reach equilibrium. b. Passive transport operates independently of concentration. c. Passive transport requires no expenditure of cellular energy. d. Passive transport operates independently of diffusion.

c. Passive transport requires no expenditure of cellular energy.

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

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

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

d. O2

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 has receptors for chemical messages. c. The plasma membrane plays a role in transferring signals to the cell's interior. d. The plasma membrane is the control center of the cell.

d. The plasma membrane is the control center of the cell.