Question 1

Which group of macromolecules does cellulose belong to?

Accepted Answer

Polysaccharides

Question 2

Cellulose is a linear polymer composed of which monomer?

Accepted Answer

$$\beta-D-$$glucose

Question 3

Which of the following best explains why ATP dissolved in water remains stable for several days, despite having a negative $$\Delta G$$ for hydrolysis?

Accepted Answer

The activation energy ($$E_A) $$for ATP hydrolysis is high.

Question 4

Which property is shared by all catalysts, including enzymes?

Accepted Answer

They lower the activation energy ($$E_A) $$required for the reaction.

Question 5

Which observation supports the induced-fit model of enzyme-substrate interaction?

Accepted Answer

X-ray diffraction shows that enzymes bound to substrate have different shapes from those without substrate.

Question 6

Which of the following is NOT a common mechanism of substrate activation by enzymes?

Accepted Answer

Covalent modification of the enzyme

Question 7

A competitive inhibitor affects enzyme activity by:

Accepted Answer

Binding to the active site and preventing substrate binding.

Question 8

Which of the following statements about allosteric regulation is TRUE?

Accepted Answer

Allosteric enzymes can be regulated by molecules other than substrates or products.

Question 9

Feedback inhibition in metabolic pathways is best described as:

Accepted Answer

The final product of a pathway inhibits an earlier step in the pathway.

Question 10

Which of the following is an example of irreversible covalent activation of an enzyme?

Accepted Answer

Proteolytic cleavage of a zymogen

Question 11

Suppose you extract enzyme X from a bacterium. Addition of a protease increases the rate of reaction catalyzed by enzyme X. What is the best explanation?

Accepted Answer

Enzyme X has been activated by proteolytic cleavage.

Question 12

Which of the following best describes the role of cofactors in enzyme activity?

Accepted Answer

Cofactors are nonprotein molecules required for some enzymes to function.

Question 13

Which class of enzyme catalyzes the transfer of a functional group from one molecule to another?

Accepted Answer

Transferases

Question 14

Which of the following statements about enzyme specificity is correct?

Accepted Answer

Enzyme specificity is due to the shape and chemistry of the active site.

Question 15

Which of the following is a likely consequence of increasing temperature above the optimal value for a human enzyme?

Accepted Answer

The enzyme will denature and lose activity.

Question 16

Which of the following best explains why enzymes are highly specific for their substrates?

Accepted Answer

The active site forms a groove or pocket with high affinity for the intended substrate.

Question 17

Which of the following is true about ribozymes?

Accepted Answer

They are RNA molecules with catalytic activity.

Question 18

Which of the following is a correct statement about the effect of a noncompetitive inhibitor?

Accepted Answer

It binds to a site other than the active site and reduces enzyme activity.

Question 19

Which of the following best describes substrate-level regulation of enzyme activity?

Accepted Answer

It depends on the interaction of substrates and products with the enzyme.

Question 20

Which of the following is a real-life example of feedback inhibition?

Accepted Answer

The end-product isoleucine inhibits threonine deaminase in the isoleucine biosynthetic pathway.

Enzymes: The Catalysts of Life – Comprehensive Study Notes

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