chapter 5

an enzyme speeds up reactions by lowering the

activation energy

an enzyme is specific because the shape of its ______matches only particular reactants.

active site

The sodium-potassium pump uses energy from ATP to move sodium ions out of the cell, and potassium ions into the cell. This is an example of

active transport.

What cannot pass directly through the phospholipids of the plasma membrane?

Charged atoms and molecules (ions)

Lactase is essential for digesting lactose in milk. This enzyme is specific for this sugar. Why?

There is a precise compatibility between the active site and the lactose molecule.

Energy can be classified as either potential or kinetic. Which of the following is an example of kinetic energy?

a running child

Which of these is exhibiting kinetic energy?

a space station orbiting Earth

Our cells require glucose to produce energy. Consider a cell where the external concentration of glucose has dropped to 5%, but the internal concentration is at 20%. How does the cell obtain more glucose?

active transport

An enzyme is considered a(n)____ because it speeds up a chemical reaction without being used up.

catalyst

In your body, what process converts the chemical energy found in glucose into the chemical energy found in ATP?

cellular respiration

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

A(n)_____, which is often a vitamin, binds to an enzyme and plays a role in catalysis.

coenzyme

high temperatures or changes in pH can _____ an enzyme, causing it to lose its shape and biological activity.

denature

The movement of molecules from an area of higher concentration to an area of lower concentration is called _____.

diffusion

The plasma membrane forms a pocket that pinches inward, forming a vesicle that contains material from outside the cell. This describes the process of

endocytosis.

"Conservation of energy" refers to the fact that _____.

energy cannot be created or destroyed but can be converted from one form to another

Through an _____ reaction, ATP is hydrolyzed into ADP by _____ and _____ energy.

exergonic ... losing a phosphate group ... releasing

A molecule moves down its concentration gradient using a transport protein in the plasma membrane. This is an example of

facilitated diffusion.

When water moves toward the solution with the _____ solute concentration, the solution is _____.

greater ... hypertonic

Which of these are by-products of cellular respiration?

heat, carbon dioxide, and water

In oil-based liquids, phospholipids are arranged so that their _____ face outward and their _____ are orientated inward.

hydrophobic tails ... hydrophilic heads

This cell is in a(n) _____ solution.

hypertonic

You know that this cell is in a(n) _____ solution because it _____.

hypertonic solution ... lost water

You know that this cell is in a(n) _____ solution because the cell _____.

hypotonic ... swelled

the ______between an active site and its substrate often strains bonds and helps the reaction proceed.

induced fit

An enzyme _____.

is an organic catalyst

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

is unchanged

what can Charged atoms and molecules (ions) pass through?

membrane transport proteins.

In active transport,

molecules move across the plasma membrane against their concentration gradient.

What name is given to the process by which water crosses a selectively permeable membrane?

osmosis

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

oxygen and carbon dioxide

Chemical energy is a form of _____ energy.

potential

Reactions can be exergonic or endergonic. Which of these reactions is endergonic?

protein synthesis

Enzymes are _____.

proteins

Enzymes work by _____.

reducing EA

In a catalyed reaction, a reactant is often called a(n)

substrate

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

substrate

Water crosses the plasma membrane

through facilitated diffusion or diffusion.