CP 1: Structure & Function of the Cell Membrane

Membrane structure

Lipid bilayer of the cell membrane

Phospholipids

Membrane fluidity

Membrane proteins

• Integral proteins: extend into or completely across cell membrane (transmembrane protein)

• Peripheral proteins: attached to either inner or outer surface of cell membrane and are easily removed from it

Integral membrane proteins

Functions of membrane proteins

Membrane proteins can act as:

• Receptor Proteins

• Cell Identity Markers

• Linkers

• Enzymes

• Ion Channels

• Transporter Proteins

Selective permeability of membrane

Membrane proteins mediate the transport of substances across the membrane that can not permeate the hydrophobic core of the lipid bilayer

Principles of diffusion

Diffusion: physical consequences

Gradients across the cell membrane

Gradients across the cell membrane

Ion gradients across the membrane

Osmosis – diffusion of H2O across membranes

Differences in osmolarity move water across membranes