Chapter 5, Problem 1CC

Fill in the following concept map to review the processes by which molecules move across membranes.

Summary Introduction

To complete: The given map showing the process by which the molecules move across the cell membrane.

Introduction:

The plasma membrane is selectively permeable, and it allows the movement of substances in and out of the cells. The two main types of transport are active transport and passive transport.

Answer to Problem 1CC

Fig. 1 shows the completed map of the process involved in the transport of molecules across the membrane.

Pictorial representation: The Fig.1 shows the movement of molecules between cells through the cell membranes.

Fig.1: The process involved in the transport of molecules across the cell membrane

Explanation of Solution

(a)

Correct answer: Active transport

Explanation: Active transport is an energy-dependent process in which the molecules are moved from a region of lower concentration to a region of higher concentration against their concentration gradient, and it requires energy in the form of ATP. Hence, the correct answer is Active transport.

(b)

Correct answer: Concentration gradient

Explanation: The concentration gradient is the difference in the concentration of the solutes. Active transport moves the molecules against their concentration gradient, whereas passive transport moves the solutes along with their concentration gradient. Hence, the correct answer is Concentration gradient.

(c)

Correct answer: Small nonpolar molecules

Explanation: A molecule is said to be nonpolar when there is a symmetrical arrangement of polar bonds in a complex molecule or if there is an equal sharing of electrons between the two atoms. These small nonpolar molecules can diffuse across the membrane. Example: Oxygen and carbon dioxide are the two nonpolar molecules that can undergo simple diffusion. Hence, the correct answer is Small nonpolar molecules.

(d)

Correct answer: Facilitated diffusion

Explanation: Facilitated diffusion is a passive transport where the molecules diffuse across the plasma membrane with the help of the membrane proteins such as carriers and channels. This transport does not require energy, and it moves the solute down the concentration gradient. Hence, the correct answer is Facilitated diffusion.

(e)

Correct answer: Transport proteins

Explanation: Transport proteins are a type of proteins used to move the substances across the cell membrane. They are mainly of two types: channel proteins and carrier proteins. Channel proteins are used to transport ions in and out of the cell, and carrier proteins are used to transport macromolecules, ions, and small molecules by changing their shape or conformation. Hence, the correct answer is Transport proteins.