Biomembrane I: Selective Permeability of Membranes

Biomembranes I: Membrane Structure and Transport

Introduction

Concept 1: Membrane Structure
Practice (1 page)
Review (1 page)

Concept 2: Osmosis: Movement of Water Across Membranes
Practice (1 page)
Review (4 pages)

Concept 3: Selective Permeability of Membranes

Practice (1 page)
Review (4 pages)

Concept 4: Passive and Active Transport
Practice (2 pages)
Review (2 pages)

Concept 5: Mechanisms of Active Transport
Practice (1 page)
Review (4 pages)

Self-Quiz

Concept 3: Selective Permeability of Membranes

Cell membranes are selectively permeable. Some solutes cross the membrane freely, some cross with assistance, and others do not cross at all.

A few lipophilic substances move freely across the cell membrane by passive diffusion. Most small molecules or ions require the assistance of specific protein carriers to transport them across the membrane. Large molecules do not cross intact cell membranes, except in certain special cases.