Biology 101 Chapter 5

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

Anything that prevents ATP formation will most likely

result in cell death

Plasma membranes are selectively permeable. This means that

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

In the reaction A→B+C+heat,

the potential energy of the products is less than that of the reactant

The active site of an enzyme is

the region of an enzyme that attaches to a substrate.

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

the second law of thermodynamics

Which of the following processes is endergonic?

the synthesis of glucose from carbon dioxide and water

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

transport proteins . . . down

Most of the functions of a cell membrane are performed by

proteins.

The molecules responsible for membrane transport are

proteins.

Cells acquire LDLs by

receptor-mediated endocytosis

Which of the following statements regarding active transport is false?

Active transport is driven by the concentration gradient.

Which of the following statements regarding thermodynamics is false?

An automobile engine is an example of a closed system

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

Cell A

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 adifferent site.

Which of the following statements regarding diffusion is false?

Diffusion occurs when particles spread from areas where they are less concentrated to areas where they are more concentrated

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 regarding enzyme function is false?

Enzymes are used up in chemical reactions.

Which of the following statements regarding enzymes is true?

Enzymes catalyze specific reactions.

What is the basic difference between exergonic and endergonic reactions?

Exergonic reactions release energy; endergonic reactions absorb it.

Which of the following statements about the ATP molecule is true?

It contains a nitrogenous base molecule called adenine.

Which of the following statements concerning energy is false?

Living systems convert heat energy into chemical energy to reduce entropy

Which of the following statements regarding membrane protein function is false?

Membrane proteins transfer genetic information to the cytoplasm.

White blood cells (WBCs) are more resistant to lysis than red blood cells (RBCs). When looking at a sample of blood for WBCs, would could you do to reduce interference from RBCs?

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

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

Na+

Which of the following statements is true among all types of passive diffusion?

The concentration gradient is the driving force.

Which of the following statements regarding membrane function is false

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?

The solute moves against the concentration gradient.

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.

Which of the following substances could be a cofactor?

a zinc atom

Substrates bind to an enzyme's ________ site

active

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

active transport

Which of the following processes could result in the net movement of a substance into a cell, if the substance is more concentrated in the cell than in the surroundings?

active transport

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

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

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?

cell-surface carbohydrates

Heating inactivates enzymes by

changing the enzyme's three-dimensional shape.

Glucose molecules provide energy to power the swimming motion of sperm. In this example, the sperm are changing

chemical energy into kinetic energy.

Inhibition of an enzyme is irreversible when

covalent bonds form between inhibitor and enzyme.

Living systems

decrease their entropy while increasing the entropy of the universe.

Phagocytosis is to eating as pinocytosis is to

drinking

Small, nonpolar, hydrophobic molecules such as fatty acids

easily pass through a membrane's lipid 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.

When a cell uses chemical energy to perform work, it couples a(n) ________ reaction with a(n) ________ reaction.

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

exhibit a net movement to the side with lower water concentration.

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

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

feedback inhibition

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

heat to light energy

The cholesterol associated with animal cell membranes

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 an d 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

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

in membrane

The fluid mosaic model describes the plasma membrane as consisting of

individual proteins and phospholipids that can drift in a phospholipid bilayer.

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

is hypotonic to the protozoan

A plant cell in a hypotonic solution

is turgid

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

isotonic to its environment.

When an enzyme catalyzes a reaction,

it lowers the activation energy of the reaction

Kinetic energy differs from chemical energy in that

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

In a hypotonic solution, an animal cell will

lyse

Most of a cell's enzymes are

proteins

Which of the following will have no effect on the rate of an enzyme-catalyzed reaction?

net change in energy

Membrane phospholipids

often have "kinks" in their tails caused by the presence of a double bond between carbons.

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

part E

Oxygen crosses a plasma membrane by

passive transport

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

passive transport.

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.

An energy barrier

prevents the spontaneous decomposition of molecules in the cell

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

protein synthesis

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

self-assembly into a simple membrane

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

signal transduction

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

structure . . . function

Osmosis can be defined as

the diffusion of water.

The energy required to initiate an exergonic reaction is called

the energy of activation

According to ________, energy cannot be created or destroyed

the first law of thermodynamics

Which of the following is a coenzyme

vitamin B6

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

you dehydrate yourself.