Chapter 3, Problem 1MC

A cell may allow a large or charged chemical to move across the cytoplasmic membrane, down the chemical’s electrical and chemical gradients, in a process called ______________________.

1. a. active transport
2. b. facilitated diffusion
3. c. endocytosis
4. d. pinocytosis

Summary Introduction

Introduction:

The basic unit of life is cell. It forms the basis for function, biological and structural unit of all living organisms. Cell biology is a branch of biology that deals with the study of the cells. Schleiden, Virchow, and Schwann’s work helped in creating cell theory which states that all organisms are composed of cells that are the basic unit of life.

Answer to Problem 1MC

Correct answer:

A cell may allow charged or large chemicals to move across the membrane, down the chemical’s electric and chemical gradient, in a process called facilitated diffusion.

Therefore, option (b) is correct.

Option (b) is given as “facilitated diffusion”.

Explanation of Solution

Justify reason for the correct statement:

Facilitated diffusion is the movement of large or charged chemical down a concentration gradient across the cytoplasmic membrane, without energy from ATP.

Hence, option (b) is correct.

Justify reasons for the incorrect statements:

Option (a) is given as “active transport”.

When molecules pass through the membrane against concentration gradient by the process of simple diffusion using ATP as energy, that process is known as active transport. The net movement of the molecule is from lower concentration to the higher concentration. Hence, it is a wrong answer.

Option (c) is given as “endocytosis”.

In endocytosis the molecules that are too large to be conveyed across the membrane of the cell are transported in the form of vesicles originate by the budding of the cell membrane. Hence, it is a wrong answer.

Option (d) is given as “pinocytosis”.

It is the process by which ingestion of liquid takes place by cell through budding from the cell membrane. Hence, it is a wrong answer.

Hence, options (a), (c), and (d) are incorrect.

Conclusion

Facilitated diffusion allow large or charged chemical to move across the membrane down the chemical gradient.