Ch. 6: Into to Metabolism

Question 1

Which of the following is an endergonic reaction?

Answer 1

Glucose + fructose → sucrose

Question 2

Which of these statements about enzyme inhibitors is true?

Answer 2

The action of competitive inhibitors may be reversible or irreversible.

Question 3

The process of stabilizing the structure of an enzyme in its active form by the binding of a molecule is an example of __________.

Answer 3

allosteric regulation

Question 4

Which of the following is changed in a reaction by the action of an enzyme?

Answer 4

The activation energy

Question 5

Metabolic pathways in cells are typically far from equilibrium. Which of the following processes tend(s) to keep these pathways away from equilibrium?

Answer 5

The continuous removal of the products of a pathway to be used in other reactions and the input of free energy from outside the pathway

Question 6

The binding of an allosteric inhibitor to an enzyme causes the rate of product formation by the enzyme to decrease. Which of the following best explains why this decrease occurs?

Answer 6

The allosteric inhibitor causes a structural change in the enzyme that prevents the substrate from binding at the active site.

Question 7

Which of the following metabolic processes can occur without a net influx of energy from some other process?

Answer 7

C6H12O6 + 6 O2 → 6 CO2 + 6 H2O [CHO + 6O > 6 CO 6 H2O]

Question 8

Which of the following environments or actions would not affect the rate of an enzyme reaction?

Answer 8

None of the listed responses is correct.

Question 9

Which of the following determines the sign of ΔG for a reaction?

Answer 9

The free energy of the reactants and the free energy of the products

Question 10

A chemical reaction is designated as exergonic rather than endergonic when __________.

Answer 10

the potential energy of the products is less than the potential energy of the reactants

Question 11

Most cells cannot harness heat to perform work because __________.

Answer 11

temperature is usually uniform throughout a cell

Question 12

What do the sign and magnitude of the ΔG of a reaction tell us about the speed of the reaction?

Answer 12

Neither the sign nor the magnitude of ΔG has anything to do with the speed of a reaction. (speed determined by Activation Energy)

Question 13

In general, the hydrolysis of ATP drives cellular work by __________.

Answer 13

releasing free energy that can be coupled to other reactions

Question 14

Organisms are described as thermodynamically open systems. Which of the following statements is consistent with this description?

Answer 14

Organisms acquire energy from, and lose energy to, their surroundings.

Question 15

What is meant by the “induced fit” of an enzyme?

Answer 15

The enzyme changes its shape slightly as it binds the substrate.

Question 16

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

Answer 16

exergonic; endergonic

Question 17

Enzyme activity is affected by pH because __________.

Answer 17

high or low pH may disrupt hydrogen bonding or ionic interactions and thus change the shape of the enzyme’s active site

Question 18

Which of the following correctly states the relationship between anabolic and catabolic pathways?

Answer 18

Anabolic pathways synthesize more complex organic molecules using the energy derived from catabolic pathways.

Question 19

Which of the following best characterizes the functional role of ATP in cellular metabolism?

Answer 19

The free energy released by ATP hydrolysis is coupled to endergonic processes via the formation of a phosphorylated intermediate.

Question 20

The formation of glucose-6-phosphate from glucose is an endergonic reaction and would, therefore, be coupled to which of the following reactions or pathways?

Answer 20

The hydrolysis of ATP

Question 21

Which of the following statements about the active site of an enzyme is correct?

Answer 21

The active site may resemble a groove or pocket in the surface of a protein into which the substrate fits.

Question 22

The binding of an allosteric inhibitor to an enzyme causes the rate of product formation by the enzyme to decrease. Which of the following best explains why this decrease occurs?

Answer 22

The allosteric inhibitor causes a structural change in the enzyme that prevents the substrate from binding at the active site.

Question 23

Which of the following statements about enzyme function is correct?

Answer 23

Enzymes can lower the activation energy of reactions, but they cannot change the equilibrium point because they cannot change the net energy output.

Question 24

If the entropy of a living organism is decreasing, which of the following is also occurring?

Answer 24

Energy is being supplied to the organism.

Question 25

Some bacteria are metabolically active in hot springs because __________.

Answer 25

their enzymes have high optimal temperatures

Question 26

Much of the suitability of ATP as an energy intermediary is related to the instability of the bonds between the phosphate groups. These bonds are unstable because __________.

Answer 26

the negatively charged phosphate groups vigorously repel one another and the terminal phosphate group is more stable in water than it is in ATP

Question 27

In general, the hydrolysis of ATP drives cellular work by __________.

Answer 27

releasing free energy that can be coupled to other reactions

Question 28

If the entropy of a living organism is decreasing, which of the following is also occurring?

Answer 28

Energy is being supplied to the organism.

Question 29

What is meant by the “induced fit” of an enzyme?

Answer 29

The enzyme changes its shape slightly as it binds the substrate.