Chapter 13. Chapter 13

Problem-Solving Video Assessment

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Chapter 13 Problem-Solving Video Assessment

E. coli bacterial cells contain a lactose permease symporter that uses the free energy of H⁺ transport into the cell to simultaneously drive entry of lactose. Typical cellular conditions include: 37°C; internal [H⁺] = 8 mM; external [H⁺] = 247 mM; membrane potential = -35 mV.

1.

What is the free-energy change associated with H⁺ transport into the cell under typical cellular conditions?

-3.4 x 10³ kJ/mol

-12.2 kJ/mol

-11.9 kJ/mol

-8.8 kJ/mol

+5.4 kJ/mol

_feedback_correct: Correct. _feedback_incorrect: Incorrect.

2.

What is the size of the lactose concentration gradient that can be generated by the free-energy input from H⁺ transport?

2 times more lactose inside of the cell

8 times more lactose inside of the cell

8 times more lactose outside of the cell

114 times more lactose inside of the cell

114 times more lactose outside of the cell

_feedback_correct: Correct. _feedback_incorrect: Incorrect.

3.

The concentration of lactose in the bacterial media is 25 μM. Given the information that you calculated above, what is the concentration of lactose inside of an E. coli cell?

219 nM

3.1 μM

119 μM

200 μM

2.9 mM

_feedback_correct: Correct. _feedback_incorrect: Incorrect.

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Chapter 13. Chapter 13

Introduction

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