chpt 5 homework

Which of the following is an accurate comparison of active transport and facilitated diffusion?

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

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?

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 about passive transport?

Passive transport requires no expenditure of cellular energy.

Small, nonpolar, hydrophobic molecules such as fatty acids

Small, nonpolar, hydrophobic molecules such as fatty acids

During enzymatic reactions, substrates are converted to products. A property of enzymes that facilitates this reaction is that they are catalysts and therefore _____.

change the rate of a reaction without being consumed by the reaction

The movement of atoms, ions, or molecules from a region of higher concentration to regions of lower concentration is called _____.

diffusion

Phagocytosis is to eating as pinocytosis is to

drinking

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

exergonic; endergonic

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?

exocytosis

What type of reaction breaks the bonds that join the phosphate groups in an ATP molecule?

hydrolosis

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

An enzyme _____.

is an organic catalyst

As a result of its involvement in a reaction, an enzyme _____.

is unchanged

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

isotonic to its environment.

Light is _____ energy, which is converted into _____ energy by plants.

kinetic ... chemical

Which of these is hydrophobic like the interior of the plasma membrane?

lipid solute molecule

know

okay

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

osmosis

Oxygen crosses a plasma membrane by

passive transport

The process of a white blood cell engulfing a bacterium is

phagocytosis

The process of a white blood cell engulfing a bacterium is

phagocytosis.

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

phosphorylation

Most enzymes are _____.

proteins

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

proteins

Enzymes work by _____.

reducing activation energy

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

remain standing upright

What name is given to the reactants in an enzymatically catalyzed reaction?

substrate

Osmosis is often viewed incorrectly as a process driven directly by differences in solute concentration across a selectively permeable membrane. What really drives osmosis?

the difference in water concentration across a selectively permeable membrane

Which part of the ATP molecule breaks free of the rest when an ATP molecule is used for energy?

the last phosphate group

Plasma membranes are selectively permeable. This means that

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

The active site of an enzyme is

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

Which of the following processes is endergonic?

the synthesis of glucose from carbon dioxide and water (photosynthesis)

Structure A in the figure is a(n) _____.

transport protein

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

transport proteins; down

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

arrangement of atoms within molecules

Aquaporins

allow water to cross the plasma membrane via facilitated diffusion.

Cellular respiration is an example of __________.

an exergonic process

Substrates bind to an enzyme's ________ site.

active

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

cell A

The cholesterol associated with animal cell membranes:

helps to keep phospholipids from being too close to one another.

Anything that prevents ATP formation will most likely

result in cell death.