Essentials of Biology (5th International Edition)
Essentials of Biology (5th International Edition)
5th Edition
ISBN: 9781259660269
Author: Sylvia S. Mader, Dr., Michael Windelspecht
Publisher: Mcgraw-Hill
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Chapter 5, Problem 1BYB
Summary Introduction

To determine:

How transport and channel proteins function in a plasma membrane?

Introduction:

Water and non-polar molecules pass across the membrane by simple diffusion through channel proteins. But, polar molecules and other macromolecules require certain proteins located in the membrane for their transport. These membrane proteins are called membrane transport protein.

Expert Solution & Answer
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Explanation of Solution

The transport proteins are of two types-

  1. Carrier proteins
  2. Channel proteins

Transport proteins perform facilitated diffusion as well as active transport.

CHANNEL PROTEINS – these are open to intracellular as well as extracellular space and are designed for passage of only a single specific substance.

Example - voltage gated channels found in neurons open up in response to change in membrane electrochemical potential and when they open, it causes bulk passage of ions through the cell.
But when closed, they do not allow any ion to pass through plasma membrane.

CARRIER PROTEINS - Open up to one side of membrane only.
They transport substances against concentration gradient and use energy to change their shape.

Example - Sodium potassium pump changes its shape using energy of ATP from being opened to intracellular environment to being open to extracellular solution allowing it to collect ions inside the cell and release them outside.

Conclusion

Hence, these proteins work in response to some or the other changes or substances response.

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The Cell Membrane; Author: The Organic Chemistry Tutor;https://www.youtube.com/watch?v=AsffT7XIXbA;License: Standard youtube license