Chapter five

Anything that prevents ATP formation will most likely

result in cell death.

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.

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

transport proteins.....down

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

Na+

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.

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.

Most of the functions of a cell membrane are preformed 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.

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

Living systems

decrease their entropy while increasing the entropy of the universe.

Small, nonpolar, hydrophobic molecules such as fatty acids

easily pass through a membrane's lipid bilayer.

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

exergonic....endergonic

The cholesterol associated with animal cell membranes

helps to stabilize the cell membrane at body temperature.

In the lab, you use a special that is permeable to water but not to 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

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 hyotonic solution

is turgid.

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? (see figure)

part E

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

signal transduction.

Osmosis can be defined as

the diffusion of water.

Americans spend up to $100 billion annually for bottled water (41 billion gallons). The only beverages with higher sales are carbonated soft drinks. Recent news stories have highlighted the fact that most bottled water comes from municipal water supplies (the same source as your tap water), although it may undergo an extra purification step called reverse osmosis. Imagine two tanks that are separated by a membrane that's permeable to water, but not to the dissolved minerals present in the water. Tank A contains tap water and Tank B contains the purified water. Under normal conditions, the purified water would cross the membrane to dilute the more concentrated tap water solution. In the reverse osmosis process, pressure is applied to the tap water tank to force the water molecules across the membrane into the pure water tank. If you shut the system off and pressure was no longer applied to Tank A, you would expect

A) the water movement to follow the concentration gradient. B) the water to revers flow from B to A. both a and b above to occur. (correct answer)

Which of the following statements regarding thermodynamics is false?

An automobile engine is an example of a closed system.

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.

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 degrees 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 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, what 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 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 and 60% water. Which of the following will occur?

Water will leave the balloon.

Americans spend up to $100 billion annually for bottled water (41 billion gallons). The only beverages with higher sales are carbonated soft drinks. Recent news stories have highlighted the fact that most bottled water comes from municipal water supplies (the same source as your tap water), although it may undergo an extra purification step called reverse osmosis. Imagine two tanks that are separated by a membrane that's permeable to water, but not to the dissolved minerals present in the water. Tank A contains tap water and Tank B contains the purified water. Under normal conditions, the purified water would cross the membrane to dilute the more concentrated tap water solution. In the reverse osmosis process, pressure is applied to the tap water tank to force the water molecules across the membrane into the pure water tank. After the reverse osmosis system has been operating for 30 minutes, the solution in tank A would

be hypertonic to tank B

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

cell A

When physicians preform an organ transplant, they choose a donor whose tissues match those of the recipients 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.

Phagocytosis is to eating as pinocytosis is to

drinking

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

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

in membranes.

The fluid mosaic model describes the plasma membrane as consisting of

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

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.

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

passive transport.

Oxygen crosses a plasma membrane by

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

Most of a cell's enzymes are

proteins.

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

Plasma membranes are selectively permeable. This means that

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

The active site of an enzyme is

the region of an enzyme that attaches to a subsrate.

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

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

you dehydrate yourself.