Chapter 10. Chapter 10

Problem-Solving Video Assessment

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Chapter 10 Problem-Solving Video Assessment

(Questions 1 & 2) Enzyme Y is an allosteric enzyme that follows the concerted model of regulation. The substrate of enzyme Y binds 250 times less tightly to the T state of the enzyme than to its R state. The ratio of [T] to [R] is 5.0 x 10¹⁰ when substrate is not bound, and enzyme Y contains six substrate binding sites.

1.

What is the ratio of enzyme molecules in the R versus T state when three substrate molecules are bound to enzyme Y?

7.8 x 10¹⁷

3.2 x 10³

3.1 x 10^-4

1.7 x 10^-9

1.3 x 10^-18

_feedback_correct: Correct. _feedback_incorrect: Incorrect.

2.

What is the ratio of enzyme molecules in the T versus R state when enzyme Y is saturated with substrate?

1.2 x 10²⁵

1.2 x 10⁹

4.9 x 10³

12.8

2.0 x 10^-4

_feedback_correct: Correct. _feedback_incorrect: Incorrect.

3.

Enzyme B is an allosteric enzyme that follows the concerted model of regulation. The substrate of enzyme B binds 85 times more tightly to the R state of the enzyme than to the T state. The ratio of [T] to [R] is 3.9 x 10⁴ when substrate is not bound to enzyme B. At substrate saturation, the ratio of [T] to [R] drops to 8.1 x 10^-4. How many substrate binding sites does enzyme B contain?

1 site

2 sites

4 sites

6 sites

8 sites

_feedback_correct: Correct. _feedback_incorrect: Incorrect.

4.

Which of the following statements concerning allosteric enzyme regulation via the concerted model is correct?

If the R enzyme conformation binds substrate more tightly than the T conformation, then the K_R dissociation constant will be larger than the K_T constant.

The smaller the difference between K_R and K_T values, the more the [T] to [R] enzyme ratio will change after substrate binding.

In the concerted model, the "L" term describes the [T] versus [R] enzyme ratio after substrate saturation.

The ratio of enzyme molecules in the [T] versus [R] state should decrease as additional substrate molecules bind to the enzyme.

In the concerted model, the [T] to [R] enzyme ratio is reduced by a factor of "i" for each substrate molecule that binds to the enzyme.

_feedback_correct: Correct. _feedback_incorrect: Incorrect.

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Chapter 10. Chapter 10

Introduction

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