Campbell Biology (12th Edition)

Published by Pearson
ISBN 10: 0135188741
ISBN 13: 978-0-13518-874-3

Chapter 7 - 7.2 - Concept Check - Page 132: 2

Answer

Movement of water molecules through the lipid bilayer is very slow due to water's molecular polarity/hydrophilic nature. While water can cross the membrane on its own, so much water has to move across membrane during the normal life of a cell that help from a transport protein is needed to provide the required speed of transport.

Work Step by Step

The key here is to see that transport is not just affected by whether a molecule can move on its own but by how much must move. This is analogous with the question in biochemistry of how quickly a reaction can proceed, not just whether it is spontaneous.
Update this answer!

You can help us out by revising, improving and updating this answer.

Update this answer

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.