BIO 181 Metabolism Quiz

1.

1 point

The active site of an enzyme is the region that: (Chapter 8)

Is inhibited by the presence of a coenzyme or a cofactor.

Binds noncompetitive inhibitors of the enzyme.

Is involved in the catalytic reaction of the enzyme.

Binds allosteric regulators of the enzyme.

2.

1 point

In glycolysis, for each molecule of glucose oxidized to pyruvate: (Chapter 9)

Two molecules of ATP are used and two molecules of ATP are produced.

Six molecules of ATP are used and six molecules of ATP are produced.

Two molecules of ATP are used and six molecules of ATP are produced.

Two molecules of ATP are used and four molecules of ATP are produced.

Four molecules of ATP are used and two molecules of ATP are produced.

3.

1 point

Proton pumps are used in various ways by members of every domain of organisms: Bacteria, Archaea, and Eukarya. According to evolution theory, what does this most probably mean? (Chapter 7)

Proton pumps must have evolved before any living organisms were present on Earth.

Cells of each domain evolved proton pumps independently when oceans became more acidic.

Proton gradients across a membrane were used by cells that were the common ancestor of all three domains of life.

Proton pumps are necessary to all cell membranes.

The high concentration of protons in the ancient atmosphere must have necessitated a pump mechanism.

4.

1 point

The primary role of oxygen in cellular respiration is to: (Chapter 9)

Combine with carbon, forming CO2.

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

Combine with lactate, forming pyruvate.

Catalyze the reactions of glycolysis.

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

5.

1 point

Increasing the substrate concentration in an enzymatic reaction could overcome which of the following? (Chapter 8)

Allosteric inhibition

Insufficient cofactors

Competitive inhibition

Saturation of the enzyme activity

Denaturization of the enzyme

6.

1 point

Energy released by the electron transport chain is used to pump H+ into which location in eukaryotic cells? (Chapter 9)

Cytosol

Mitochondrial matrix

Mitochondrial outer membrane

Mitochondrial inner membrane

Mitochondrial intermembrane space

7.

1 point

Phosphofructokinase is an allosteric enzyme that catalyzes the conversion of fructose 6-phosphate to fructose 1,6-bisphosphate, an early step of glycolysis. In the presence of oxygen, an increase in the amount of ATP in a cell would be expected to: (Chapter 9)

Inhibit the enzyme and thus slow the rates of glycolysis and the citric acid cycle.

Inhibit the enzyme and thus increase the rates of glycolysis and the citric acid cycle.

Activate the enzyme and increase the rates of glycolysis and the citric acid cycle.

Activate the enzyme and thus slow the rates of glycolysis and the citric acid cycle.

Inhibit the enzyme and thus increase the rate of glycolysis and the concentration of citrate.

8.

1 point

A chemical reaction that has a positive ΔG is correctly described as: (Chapter 8)

Endergonic

Enthalpic

Spontaneous

Exothermic

Endothermic

9.

1 point

Which of the following is (are) true for anabolic pathways? (Chapter 8)

They consume energy to decrease the entropy of the organism and its environment.

They consume energy to build up polymers from monomers.

They are usually highly spontaneous chemical reactions.

They do not depend on enzymes.

They release energy as they degrade polymers to monomers.

10.

1 point

Where is ATP synthase located in the mitochondrion? (Chapter 9)

Mitochondrial matrix

Inner membrane

Electron transport chain

Cytosol

Outer membrane

11.

1 point

Which of the following statements is correct about diffusion? (Chapter 7)

It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration.

It requires an expenditure of energy by the cell.

It is very rapid over long distances.

It requires integral proteins in the cell membrane.

It is an active process in which molecules move from a region of lower concentration to one of higher concentration.

12.

1 point

Which of the following is a reasonable explanation for why unsaturated fatty acids help keep any membrane more fluid at lower temperatures? (Chapter 7)

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.

Unsaturated fatty acids have a higher cholesterol content and therefore more cholesterol in membranes.

The double bonds result in shorter fatty acid tails and thinner membranes.

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

13.

1 point

A cell has the following molecules and structures: enzymes, DNA, ribosomes, plasma membrane, and mitochondria. It could be a cell from _____. (Chapter 6)

a bacterium

an animal, but not a plant

any kind of organism

nearly any eukaryotic organism

any multicellular organism, like a plant or an animal

14.

1 point

Some bacteria are metabolically active in hot springs because: (Chapter 8)

They are able to maintain a lower internal temperature.

Their enzymes are completely insensitive to temperature.

Their enzymes have high optimal temperatures.

High temperatures make catalysis unnecessary.

They use molecules other than proteins or RNAs as their main catalysts.

15.

1 point

Starting with one molecule of isocitrate and ending with fumarate, how many ATP molecules can be made through substrate-level phosphorylation (see Figure 9.2)? (Chapter 9)

24

2

1

12

11

16.

1 point

According to the induced fit hypothesis of enzyme catalysis, which of the following is correct? (Chapter 8)

The active site creates a microenvironment ideal for the reaction.

A competitive inhibitor can outcompete the substrate for the active site.

Some enzymes change their structure when activators bind to the enzyme.

The binding of the substrate changes the shape of the enzyme's active site.

The binding of the substrate depends on the shape of the active site.

17.

1 point

Which of the following statements is true concerning catabolic pathways? (Chapter 6)

They are endergonic.

They combine molecules into more energy-rich molecules.

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

They are spontaneous and do not need enzyme catalysis.

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

18.

1 point

Which of the following is a statement of the first law of thermodynamics? (Chapter 8)

Kinetic energy is stored energy that results from the specific arrangement of matter.

The entropy of the universe is constant.

Energy cannot be created or destroyed

Energy cannot be transferred or transformed.

The entropy of the universe is decreasing.

19.

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: (Chapter 8)

Metabolic inhibition.

Allosteric inhibition.

Reversible inhibition.

Noncooperative inhibition.

Feedback inhibition.

20.

1 point

Which of the following statements describes NAD+? (Chapter 9)

NAD+ is oxidized by the action of hydrogenases.

NAD+ has more chemical energy than NADH.

NAD+ can donate electrons for use in oxidative phosphorylation.

In the absence of NAD+, glycolysis can still function.

NAD+ is reduced to NADH during glycolysis, pyruvate oxidation, and the citric acid cycle.

21.

1 point

How might an amino acid change at a site distant from the active site of the enzyme alter the enzyme's substrate specificity? (Chapter 8)

By changing the enzyme's stability.

An amino acid change away from the active site cannot alter the enzyme's substrate specificity.

By changing the enzyme's PH optimum.

By changing the shape of the protein.

By changing the enzyme's location in the cell.

22.

1 point

Why is glycolysis described as having an investment phase and a payoff phase? (Chapter 9)

It both splits molecules and assembles molecules.

It uses stored ATP and then forms a net increase in ATP.

It shifts molecules from cytosol to mitochondrion.

It uses glucose and generates pyruvate.

It attaches and detaches phosphate groups.

23.

1 point

Why isn't the mitochondrion classified as part of the endomembrane system? (Chapter 6)

Its structure is not derived from the ER or Golgi.

It is a static structure.

It is not attached to the outer nuclear envelope.

It is not involved in protein synthesis.

It has too many vesicles.

24.

1 point

When chemical, transport, or mechanical work is done by an organism, what happens to the heat generated? (Chapter 8)

It is used to generate ADP from nucleotide precursors.

It is used to power yet more cellular work.

It is lost to the environment.

It is transported to specific organs such as the brain.

It is used to store energy as more ATP.

25.

1 point

According to the fluid mosaic model of cell membranes, which of the following is a true statement about membrane phospholipids? (Chapter 7)

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

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

They occur in an uninterrupted bilayer, with membrane proteins restricted to the surface of the membrane.

They can move laterally along the plane of the membrane.

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

26.

1 point

How does a noncompetitive inhibitor decrease the rate of an enzyme reaction? (Chapter 8)

By acting as a coenzyme for the reaction.

By changing the shape of the enzyme's active site.

By changing the free energy change of the reaction.

By binding at the active site of the enzyme.

By decreasing the activation energy of the reaction.

27.

1 point

The following question is based on the reaction A + B ↔ C + D shown in Figure 8.1.
Which of the following represents the activation energy required for the enzyme-catalyzed reaction in Figure 8.1? (Chapter 8)

A

B

C

D

E

28.

1 point

The molecule that functions as the reducing agent (electron donor) in a redox or oxidation-reduction reaction: (Chapter 9)

Gains electrons and gains potential energy.

Loses electrons and gains potential energy.

Gains electrons and loses potential energy.

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

Loses electrons and loses potential energy.

29.

1 point

In a plant cell, DNA may be found _____. (Chapter 6)

only in the nucleus and chloroplasts

only in the nucleus

In the nucleus, mitochondria, and chloroplasts

In the nucleus, mitochondria, chloroplasts, and peroxisomes

only in the nucleus and mitochondira

30.

1 point

In cellular respiration, the energy for most ATP synthesis is supplied by: (Chapter 9)

Converting oxygen to atp.

Generating carbon dioxide and oxygen in the electron transport chain.

A proton gradient across a membrane.

High energy phosphate bonds in organic molecules.

Transferring electrons from organic molecules to pyruvate.

31.

1 point

What is the term for metabolic pathways that release stored energy by breaking down complex molecules? (Chapter 9)

Anabolic pathways

Thermodynamic pathways

Bioenergetic pathways

Fermentation pathways

Catabolic pathways

32.

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? (Chapter 9)

Acetyl coa

Glyceraldehydes-3-phosphate

Citrate

Oxaloacetate

Lactate

33.

1 point

When skeletal muscle cells undergo anaerobic respiration, they become fatigued and painful. This is now known to be caused by: (Chapter 9)

Increase in ethanol.

Increase in sodium ions.

Buildup of pyruvate.

Buildup of lactate.

34.

1 point

Which of the following produces the most ATP when glucose (C6H12O6) is completely oxidized to carbon dioxide (CO2) and water? (Chapter 9)

Fermentation

Glycolysis

Oxidation of pyruvate to acetyl coa

Citric acid cycle

Oxidative phosphorylation (chemiosmosis)

35.

1 point

The following question is based on the reaction A + B ↔ C + D shown in Figure 8.1.
Which of the following represents the ΔG of the reaction in Figure 8.1? (Chapter 8)

A

B

C

D

E

36.

1 point

Which of the following statements describes the results of this reaction?
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy (Chapter 9)

O2 is oxidized and H2O is reduced.

CO2 is reduced and O2 is oxidized.

C6H12O6 is reduced and CO2 is oxidized.

O2 is reduced and CO2 is oxidized.

C6H12O6 is oxidized and O2 is reduced.

37.

1 point

Which curves on the graphs may represent the temperature and pH profiles of an enzyme taken from a bacterium that lives in a mildly alkaline hot springs at temperatures of 70°C or higher?
Activity of various enzymes at various temperatures (a) and at various pH (b). (Chapter 8)

Curves 1 and 5

Curves 3 and 4

Curves 2 and 5

Curves 3 and 5

Curves 2 and 4

38.

1 point

Which of the following is an example of cooperativity? (Chapter 8)

The binding of an end product of a metabolic pathway to the first enzyme that acts in the pathway.

The effect of increasing temperature on the rate of an enzymatic reaction.

A molecule binding at one unit of a tetramer, allowing faster binding at each of the other three.

One enzyme in a metabolic pathway passing its product to act as a substrate for the next enzyme in the pathway.

Binding of an ATP molecule along with one of the substrate molecules in an active site.

39.

1 point

Which process in eukaryotic cells will proceed normally whether oxygen (O2) is present or absent? (Chapter 9)

Chemiosmosis

The citric acid cycle

Oxidative phosphorylation

Glycolysis

Electron transport

40.

1 point

Which of the following occurs in the cytosol of a eukaryotic cell? (Chapter 9)

Citric acid cycle

Oxidation of pyruvate to acetyl CoA

Glycolysis and fermentation

Oxidative phosphorylation

Fermentation and chemiosmosis