Chapter 36. Problem 36.24

Problem-Solving Video Assessment

true

false

Problem 36.24: Minimal Concentration

Scientists studying the pathogenic bacterial species M. tuberculosis discover a new transcriptional regulator, RegX, which controls the expression of numerous stress-related genes located in the stress operon within the cell. The scientists determine that approximately five molecules of RegX are present in each cell.

1.

What is the concentration of RegX in these bacterial cells? Assume that the volume of an M. tuberculosis cell is 10^-8 cm³.

3.3 x 10^-17 M

8.3 x 10^-16 M

3.3 x 10^-14 M

1.7 x 10^-13 M

8.3 x 10^-13 M

_feedback_correct: Correct. _feedback_incorrect: Incorrect.

2.

The K_d for RegX binding to DNA is 0.05 pM. Which of the following statements is true?

The cellular concentration of RegX is higher than the K_d, so RegX is bound to DNA.

The cellular concentration of RegX is lower than the K_d, so RegX is bound to DNA.

The cellular concentration of RegX is higher than the K_d, so RegX is free in the cell.

The cellular concentration of RegX is lower than the K_d, so RegX is free in the cell.

The cellular concentration of RegX is equal to the K_d, so it is equally bound and free.

_feedback_correct: Correct. _feedback_incorrect: Incorrect.

3.

Further study of RegX uncovers a small protein chaperone, Hsp2, which is upregulated during cellular stress and acts as an inducer of RegX. Furthermore, the regulation of RegX appears to be controlled in a manner homologous to the lac repressor. Given this information, which of the following statements is incorrect?

Under nonstressed conditions, genes in the stress operon are repressed.

Hsp2 association induces RegX to bind to the stress operon and activate transcription.

Binding of Hsp2 prevents RegX from binding to the stress operon.

Loss of RegX binding leads to expression of genes in the stress operon.

RegX remains tightly bound to the stress operon during nonstressed conditions.

_feedback_correct: Correct. _feedback_incorrect: Incorrect.

Activity results are being submitted...

Chapter 36. Problem 36.24

Introduction

1.

2.

3.