Ch. 6: Into to Metabolism Flashcards

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1
Q

Which of the following is an endergonic reaction?

A

Glucose + fructose → sucrose

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2
Q

Which of these statements about enzyme inhibitors is true?

A

The action of competitive inhibitors may be reversible or irreversible.

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3
Q

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

A

allosteric regulation

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4
Q

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

A

The activation energy

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5
Q

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

A

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

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6
Q

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?

A

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

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7
Q

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

A

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

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8
Q

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

A

None of the listed responses is correct.

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9
Q

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

A

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

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10
Q

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

A

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

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11
Q

Most cells cannot harness heat to perform work because __________.

A

temperature is usually uniform throughout a cell

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12
Q

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

A

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

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13
Q

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

A

releasing free energy that can be coupled to other reactions

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14
Q

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

A

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

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15
Q

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

A

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

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16
Q

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

A

exergonic; endergonic

17
Q

Enzyme activity is affected by pH because __________.

A

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

18
Q

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

A

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

19
Q

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

A

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

20
Q

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?

A

The hydrolysis of ATP

21
Q

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

A

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

22
Q

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?

A

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

23
Q

Which of the following statements about enzyme function is correct?

A

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

24
Q

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

A

Energy is being supplied to the organism.

25
Q

Some bacteria are metabolically active in hot springs because __________.

A

their enzymes have high optimal temperatures

26
Q

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 __________.

A

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

27
Q

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

A

releasing free energy that can be coupled to other reactions

28
Q

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

A

Energy is being supplied to the organism.

29
Q

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

A

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