Cell Membrane Structure and Function in Biosci107

Fluid Mosaic Model

Membrane structure described as lipids and proteins.

Selective Permeability

Membrane allows certain substances to cross.

Phospholipids

Comprise 75% of membrane lipids.

Phospholipid Bilayer

Two parallel layers of phospholipids.

Amphipathic Molecules

Molecules with both polar and nonpolar regions.

Membrane Fluidity

Ability of lipids to move within membrane.

Lipid Tail Length

Longer tails decrease membrane fluidity.

Double Bonds in Lipids

More double bonds increase membrane fluidity.

Cholesterol's Role

Increases membrane stability, decreases fluidity.

Integral Membrane Proteins

Proteins that span the lipid bilayer.

Peripheral Membrane Proteins

Proteins attached to membrane surface.

Receptor Proteins

Proteins that receive chemical signals.

Transporter Proteins

Proteins that facilitate substance movement.

Ion Channels

Proteins that allow ion passage through membranes.

Diffusion

Movement from high to low concentration.

Equilibrium in Diffusion

Even distribution of particles in a solution.

Concentration Gradient

Difference in concentration across a membrane.

Osmosis

Water movement across a selectively permeable membrane.

Aquaporins

Proteins that facilitate water transport.

Osmotic Pressure

Pressure preventing water flow across a membrane.

Membrane Potential

Electrical gradient across the cell membrane.

Electrochemical Gradient

Influence of charge and concentration on ion movement.

Diffusion Distance

Greater distance slows the rate of diffusion.

Cell Size Limit

Rate of diffusion limits cell size to 20 µm.