Test 2 Practice

1.

1 point

Which of the following types of molecules are the major structural components of the cell membrane?

Ch. 7

phospholipids and cellulose

nucleic acids and proteins

phospholipids and proteins

glycoproteins and cholesterol

2.

1 point

According to the fluid mosaic model of cell membranes, which of the following is a true statement about membrane phospholipids?

they are free to depart from the membrane and dissolve in the surrounding solution

they have hydrophilic tails in the interior of the membrane

they can move laterally along the plane of the membrane

they frequently flip-flop from one side of the membrane to the other

they occur in a uninterrupted bilayer, with membrane proteins restricted to the surface of the membrane

3.

1 point

In order for a protein to be an integral membrane protein it would have to be

exposed on only one surface of the membrane

completely covered with phospholipids

hydrophobic

amphipathic, with at least one hydrophobic region

hydrophilic

4.

1 point

Which of the following is a reasonable explanation for why unsaturated fatty acids help keep any membrane more fluid at lower temperatures?

the double bonds block interaction among the hydrophilic head groups of the lipids

Unsaturated fatty acids have higher cholesterol content

The double bonds form kinks in the fatty acid tails, preventing adjacent lipids from packing tightly

Unsaturated fatty acids are more polar than saturated fatty acids

5.

1 point

Which of these are not embedded in the hydrophobic region of the lipid bilayer at all?

glycoproteins

integral proteins

integrins

transmembrane proteins

peripheral proteins

6.

1 point

Cell membranes are asymmetrical. Which of the following is the most likely explanation?

Cell membrane forms a border between once cell and another in tightly packed tissues such as epithelium

the two sides of the membrane face different environments and carry out different functions

the "innerness" and "outerness" of membrane surfaces are predetermined by genes

proteins can only be associated with the cell membrane on the cytoplasmic side.

Cell membranes communicate signals from one organism to another

7.

1 point

What kinds of molecules pass through a cell membrane most easily?

large polar

large and hydrophobic

monosaccharides

ionic

small and hydrophobic

8.

1 point

Which of the following would likely move through the lipid bilayer of a plasma membrane most rapidly?

glucose

K+

starch

CO2

an amino acid

9.

1 point

Celery stalks that are immersed in fresh water for several hours become stiff and hard. Similar stalks left in a 0.15M salt solution become limp and soft. From this we can deduce that the cells of the celery stalks are

hypertonic to freshwater, but hypotonic to the salt solution

hypotonic to freshwater, but hypertonic to the salt solution

hypertonic to both freshwater and the salt solution

hypotonic to both freshwater and salt solution

isotonic with freshwater, but hypotonic to the salt solution

10.

1 point

What is the voltage across a membrane called?

electrochemical gradient

osmotic potential

chemical gradient

membrane potential

water potential

11.

1 point

When a plant cell, such as one from a peony stem, is submerged in a very hypotonic solution, what is likely to occur?

The cell will burst

The cell will become turgid.

The cell will become flaccid

The cell membrane will lyse

Plasmolysis will shrink the interior

12.

1 point

Ions diffuse across membranes through specific ion channels

down their chemical gradients

down their electrochemical gradients

down their concentration gradients

down the osmotic potential gradients

down their electrical gradient

13.

1 point

Which of the following would increase the electrochemical potential across a membrane?

a proton pump

a chloride channel

a potassium channel

both a proton pump and a potassium channel

a sucrose-proton cotransporter

14.

1 point

The sodium-potassium pump is called an electrogenic pump because it

pumps hydrogen ions out of the cell

is used to drive the transport of other molecules against a concetration gradient

contributes to the membrane potential

ionizes sodium and potassium atoms

pumps equal quantities of Na+ and K+ across the membrane

15.

1 point

Which of the following statements correctly describes the normal tonicity conditions for typical plant and animal cells?

the animal cell is in a hypotonic solution and the plant cell is in an isotonic solution

the animal cell is in a hypertonic solution, and the plant cell is in a hypotonic solution.

The animal cell is in an isotonic solution, and the plant cell is in a hypertonic solution

The animal cell is in a hypertonic solution, and the plant cell is in an isotonic solution

the animal cell is in an isotonic solution, and the plant cell is in a hypotonic solution

16.

1 point

Which term most precisely describes the cellular process of breaking down large molecules into smaller ones?

catalysis

anabolism

dehydration

metabolism

catabolism

17.

1 point

For living organisms, which of the following is an important consequence of the first law of thermodynamics?

The energy content of an organism is constant

The entropy of an organism decreases with time as the organism grows in complexity

organisms grow by converting energy into organic matter

life does not obey the first law of thermodynamics

The organism ultimately must obtain all of the necessary energy for life from its environment

18.

1 point

Whenever energy is transformed, there is always an increase in the

enthalpy of the universe

entropy of the system

free energy of the universe

free energy of the systems

entropy of the universe

19.

1 point

A chemical reaction that has a positive ∆G is correctly described as

exothermic

spontaneous

endothermic

endergonic

enthalpic

20.

1 point

Why is ATP an important molecule in metabolism?

Its terminal phosphate group contains a strong covalent bond that, when hydrolyzed, releases free energy.

Its hydrolysis provides an input of free energy for exergonic reactions

Its terminal phosphate bond has higher energy than the other two.

It provides energy coupling between exergonic and endergonic reactions.

21.

1 point

Which of the following statements is true concerning catabolic pathways?

They supply energy, primarily in the form of ATP, for the cell's work

They combine molecules into more energy-rich molecules.

They build up complex molecules such as protein from simpler compounds.

They are endergonic

22.

1 point

Reactants capable of interacting to form products in a chemical reaction must first overcome a thermodynamic barrier known as the reaction's

equilibrium point

entropy

free-energy content

endothermic level

activation energy

23.

1 point

Which of the following statements regarding enzymes is true?

Enzymes increase the rate of a reaction by lowering the activation energy barrier.

Enzymes increase the rate of a reaction by making the reaction more exergonic.

Enzymes change the equilibrium point of the reactions they catalyze

Enzymes make the rate of reaction independent of substrate concentrations

Enzymes increase the rate of a reaction by reducing the rate of reverse reactions

24.

1 point

The active site can lower an activation energy barrier by all of the following methods EXCEPT:

Ionically bonding to the stubstrate

Providing a favorable microenvironment

Covalently bonding to the substrate

Orienting substrates correctly

Straining substrate bonds

25.

1 point

The mechanism in which the end product of a metabolic pathway inhibits an earlier step in the pathway is most precisely described as

feedback inhibition

noncooperative inhibition

allosteric inhibition

reversible inhibition

metabolic inhibition

26.

1 point

Choose the pair of terms that correctly completes this sentence: Catabolism is to anabolism as ___________ is to ____________.

work; energy

entropy; enthalpy

free energy; entropy

exergonic; endergonic

exergonic; spontaneous

27.

1 point

If an enzyme in solution is saturated with substrate, the most effective way to obtain a faster yield of products is to

add more of the enzyme

add more substrate

add an allosteric inhibitor

add a noncompetitive inhibitor

heat the solution to 90 degrees celsius

28.

1 point

If an enzyme is added to a solution where its substrate and product are in equilibrium, what will occur?

the free energy of the system will change

the reaction will change from endergonic to exergonic

additional product will be formed

nothing; the reaction will stay at equilibrium

additional substrate will be formed

29.

1 point

How does a noncompetitive inhibitor decrease the rate of an enzyme reaction?

by binding at the active site of the enzyme

by changing the free energy change of the reaction

by decreasing the activation energy of the reaction

by acting as a coenzyme for the reaction

by changing the shape of the enzyme's active site

30.

1 point

The binding of an _____________ stabilizes the active form of the enzyme. The binding of an _____________ stabilizes the inactive form of the enzyme.

stabilizer; inactivator

activator; inhibitor

inhibitor; activator

activator; stablizer

31.

1 point

The molecule that functions as the reducing agent in a redox or oxidation-reduction reaction

loses electrons and gains potential energy.

gains electrons and gains potential energy.

neither gains nor loses electrons, but gains or loses potential energy.

gains electrons and loses potential energy.

loses electrons and loses potential energy.

32.

1 point

Which of the following statements describes the results of this reaction? C6H12O6 + 6O2 → 6CO2 + 6H2O + energy

O2 is oxidized and H2O is reduced

C6H12O6 is oxidized and O2 is reduced

CO2 is reduced and O2 is oxidized

C6H12O6 is reduced and CO2 is oxidized

O2 is reduced and CO2 is oxidized

33.

1 point

When a glucose molecule loses a hydrogen atom as the result of an oxidation-reduction reaction, the molecule becomes

hydrolyzed

reduced

oxidized

hydrogenated

34.

1 point

Which of the following produces the most ATP when glucose is completely oxidized to carbon dioxide and water?

oxidative phosphorylation (chemiosmosis)

glycolysis

fermentaiton

citric acid cycle

oxidation of pyruvate to acetyl CoA

35.

1 point

Where does glycolysis take place in eukaryotic cells?

mitochondrial inner membrane

mitochondrial matrix

mitochondrial intermembrane space

cytosol

mitochondrial outer membrane

36.

1 point

Why is glycolysis described as having an investment phase and a payoff phase?

it attaches and detaches phosphate groups

it uses stored ATP and then forms a net increase in ATP

it uses glucose and generates pyruvate

it both splits molecules and assembles molecules

it shifts molecules from cytosol to mitochondrion

37.

1 point

The primary role of oxygen in cellular respiration is to

combine with lactate, forming pyruvate.

act as an acceptor for electrons and hydrogen, forming water.

combine with carbon, forming CO2.

yield energy in the form of ATP as it is passed down the respiratory chain.

catalyze the reactions of glycolysis.

38.

1 point

How many oxygen molecules are required each time a molecule of glucose is completely oxidized to carbon dioxide and water via aerobic respiration?

1

12

6

30

3

39.

1 point

Which of the following normally occurs in eukaryotic cells regardless of whether or not oxygen is present?

oxidation of pyruvate to acetyl CoA

glycolysis

citric acid cycle

oxidative phosphorylation (chemiosmosis)

fermentation

40.

1 point

Which metabolic pathway is common to both fermentation and cellular respiration of a glucose molecule?

glycolysis

reduction of pyruvate to lactate

the electron transport chain

the citric acid cycle

synthesis of acetyl CoA from pyruvate

41.

1 point

What is a proton-motive force?

the force required to remove an electron from hydrogen

the force that moves hydrogen into the mitochondrion

the force that moves hydrogen to NAD+

the force that moves hydrogen into the intermembrane space

the force exerted on a proton by a transmembrane proton concentration gradient

42.

1 point

Which of the following intermediary metabolites enters the citric acid cycle and is formed, in part, by the removal of a carbon (CO2) from one molecule of pyruvate?

acetyl CoA

glyceraldehydes-3-phosphate

citrate

oxaloacetate

lactate

43.

1 point

Why does the oxidation of organic compounds by molecular oxygen to produce CO2 and water release free energy?

the electrons have a higher potential energy when associated with water and CO2 than they do in organic compounds.

Electrons are being moved from atoms that have a lower affinity for electrons (such as C) to atoms with higher affinity such as O

the oxidation of organic compounds can be used to make ATP

the covalent bonds in organic molecules and molecular oxygen have more kinetic energy than the covalent bonds in water and carbon dioxide

the covalent bond in O2 is unstable and easily broken by electrons from organic molecules.

44.

1 point

Where are the proteins of the electron transport chain located?

cytosol

mitochondrial outer membrane

mitochondrial matrix

mitochondrial intermembrane space

mitochondrial inner membrane

45.

1 point

The synthesis of ATP by oxidative phosphorylation, using the energy released by movement of protons across the membrane down their electrochemical gradient, is an example of

allosteric regulation

a reaction with a positive ΔG

active transport

an endergonic reaction coupled to an exergonic reaction

osmosis

46.

1 point

Which of the events listed below occurs in the light reactions of photosynthesis?

NADPH is reduced to NADP+

NADP is produced

Light is absorbed and funneled to reaction-center chlorophyll a

Carbon dioxide is incorporated into PGA

ATP is phosphorylated to yield ADP

47.

1 point

What are the products of linear photophosphorylation?

P700 and P680

ATP and NADPH

ADP and NADP

ATP and P700

heat and fluorescence

48.

1 point

Generation of proton gradients across membranes occurs during

neither photosynthesis nor respiration

both photosynthesis and respiration

photosynthesis

photorespiration

respiration

49.

1 point

What is the relationship between wavelength of light and the quantity of energy per photon?

they are separate phenomena

they have a direct, linear relationship

they are inversely related

they are only related in certain parts of the spectrum

they are logarithmically related

50.

1 point

Which of the following statements is a correct distinction between autotrophs and heterotrophs?

only heterotrophs require oxygen

only heterotrophs have mitochondria

only heterotrophs require chemical compounds from the environment.

autotrophs, but not heterotrophs, can nourish themselves with CO2 and other nutrients that are inorganic

cellular respiration is unique to heterotrophs