Chapter 9, Problem 6A

Summary Introduction

Introduction:

A cell grows until it reaches its size limit, then it either stops growing or divides. Most cells undergo division. Cell division helps a cell to reproduce and makes the organism grow and heal certain injuries. Most cells are less than 100μm in diameter. The ratio of surface area to volume is the key factor that limits the size of a cell.By remaining small cells have a higher ratio of surface area to volume and they can sustain themselves more easily.

Answer to Problem 6A

Correct answer :

The correct answer is option B. plasma membrane

Explanation of Solution

Explanation/justification for the correct answer:

Option B. plasma membrane- Surface area of a cell refers to the area covered by the plasma membrane through which the nutrients and wastes must pass through. It can be calculated by multiplying length, width and number of sides. Small cells have high ratio of surface area to volume. If a cell grows in size, its surface area increases but its volume increases more rapidly. This results in low ratio of surface area to volume. This causes difficulty in supplying nutrients and expelling wastes from the cell.

Hence this is the correct option.

Explanation for incorrect answer:

Option A. nucleus−Surface area of a cell refers to the area covered by the plasma membrane through which the nutrients and wastes must pass through. It does not refer to the nucleus.

Hence, this is not the correct option.

Option C. mitochondria- Surface area of a cell refers to the area covered by the plasma membrane through which the nutrients and wastes must pass through. It does not refer to the mitochondria in the cell.

Hence this is not the correct option.

Option D. cytoplasm- Surface area of a cell refers to the area covered by the plasma membrane through which the nutrients and wastes must pass through. It does not refer to the cytoplasm in the cell.

Hence this is not the correct option.