5.1
What Is the Structure of a Biological
Membrane? 97
Lipids constitute the bulk of a membrane
97
Membrane proteins are asymmetrically
distributed 99
Membranes are dynamic 100
Membrane carbohydrates are recognition
sites 101
5.2
How Is the Plasma Membrane Involved
in Cell Adhesion and Recognition?
102
Cell recognition and cell adhesion
involve proteins at the cell surface
102
Three types of cell junctions connect
adjacent cells 102
5.3
What Are the Passive Processes of
Membrane Transport? 105
Diffusion is the process of random
movement toward a state of equilibrium
105
Simple diffusion takes place through
the phospholipid bilayer 106
Osmosis is the diffusion of water
across membranes 106
Diffusion may be aided by channel
proteins 108
Carrier proteins aid diffusion by
binding substances 110
5.4 How Do Substances Cross Membranes
against a Concentration Gradient?
111
Active transport is directional 111
Primary and secondary active transport
rely on different energy sources 111
5.5 How
Do Large Molecules Enter and Leave
a Cell? 113
Macromolecules and particles enter
the cell by endocytosis 113
Receptor-mediated endocytosis is highly
specific 113
Exocytosis moves materials out of
the cell 114
5.6 What Are Some Other Functions
of Membranes? 114
