Which of the following structures is primarily responsible for regulating the movement of substances into and out of a bacterial cell?

• A. Cell wall
• B. Flagellum
• C. Capsule
• D. Plasma membrane

Answer: (D)

Verified step by step guidance

1. Understand the function of each bacterial cell structure listed: the cell wall, flagellum, capsule, and plasma membrane.
2. Recall that the cell wall provides structural support and shape to the bacterial cell but does not regulate substance movement.
3. Recognize that the flagellum is involved in bacterial motility, helping the cell move, not controlling substance entry or exit.
4. Know that the capsule is a protective layer outside the cell wall that helps in defense and adhesion but does not regulate transport.
5. Identify that the plasma membrane is a selectively permeable barrier that controls the movement of substances into and out of the bacterial cell, making it the correct answer.