Biology Test 2 Chapter 5

Which of these is ATP?

(Ribose, Three P's)

Requires energy from the cell. Molecules move against their concentration gradient.

Active Transport.

A vesicle inside the cell fuses with the plasma membrane and releases its contents outside the cell

Exocytosis

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

Na+

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?

Water will leave the balloon.

An enzyme speeds up reactions by lowering the

activation energy

Most of a cell's enzymes are

proteins

Osmosis can be defined as

the diffusion of water.

Plasma membranes are selectively permeable. This means that

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

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

transport proteins; down

What substance is transported by aquaporins?

water

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

you dehydrate yourself.

A form of passive transport. Molecules move across the plasma membrane using a transport protein.

Facilitated Diffusion

Fluidity of an animal cell plasma membrane is enhanced by __________.

cholesterol molecules

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

coenzyme

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

proteins

Which of the following statements regarding active transport is false?

Active transport is driven by the concentration gradient.

Which of the following is a difference between active transport and facilitated diffusion?

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

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

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

A form of passive transport. Molecules move across the plasma membrane by crossing the lipid bilayer.

Diffusion

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

Endocytosis

Which of the following statements regarding enzymes is true?

Enzymes catalyze specific reactions.

The energy required to initiate an exergonic reaction is called

activation energy.

Substrates bind to an enzyme's ________ site.

active

An enzyme is specific because the shape of its ____ matches only particular reactants.

active site

Cellular respiration is an example of __________.

an exergonic process

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

catalyst

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

cell A

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

Heating inactivates enzymes by

changing the enzyme's three-dimensional shape.

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

denature

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

diffusion

The fluid mosaic model describes the plasma membrane as consisting of

diverse proteins embedded in a phospholipid bilayer.

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

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

A specific _____ speeds up each of a cell's chemical reactions.

enzyme

Through energy coupling, cells use_____, or energy-releasing, reactions to drive ______, or energy-requiring, reactions. The molecule ___ is the energy shuttle between these two types of reactions.

exergonic, endergonic, ATP

Mechanisms such as _____ enable precise control over a cell's metabolism -- all of its chemical reactions.

feedback inhibition, metabolism

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

hydrolysis

A plant cell placed in a(n) _____solution will lose water and plasmolyze

hypertonic

There is a net diffusion of water out of an animal cell when it is placed in a(n) _____ solution

hypertonic

An animal cell placed in a(n) ______ solution will gain water, swell, and possibly burst.

hypotonic

The ideal osmotic environment for a plant cell is a(n) _____ environment.

hypotonic

The _____ between an active site and its substrate often strains bonds and helps the reaction proceed.

induced fit

A plant cell surrounded by a(n) _____ solution will be flaccid (limp).

isotonic

The ideal osmotic environment for an animal cell is a(n) _____ environment.

isotonic

The mechanism of enzyme action is to _____.

lower the energy of the activation of a reaction

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

oxygen and carbon dioxide

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

part D

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

passive transport.

There are three main types of cellular work: chemical, transport, and movement. Most of this work is powered by the transfer of a phosphate group from one molecule to another in a process known as

phosphorylation

The lipids in a cell membrane are arranged _____.

so that the nonpolar parts of two lipids point toward each other

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

substrate

The transport of molecules of a particular solute from inside an animal cell across the cell membrane to the extracellular fluid always requires energy when _____.

the concentration of the solute is lower inside the cell than outside it

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