Major Concepts to Review for AP Biology

Cell Transport ( Membrane Funtions)

 

Plasma membrane's

Structure:
lipid bilayer phospholipids + Cholesterol to adjust fluidity

various proteins - transmembraneal, Integral, periferal, surface

Fluid mosic Model

Directional with distince inside and outside with may not be switched

Turnover is constant new membrane added (exocytosis) and old removed (endocytosis)

 

Function:
Depends on type of proteins

General functions: Barrier, import and export of materials, homeostasis, maintenance of chemical gradients (including action potential), detection of stimuli (like hormones, light etc.)

 

Special junctions designed for communication between adjacent cells

 

Gap Junctions - animals

Plasmodesmata - plants

 

Mechanisms of Transport
Passive Transport

Diffusion (heat)

Osmosis, water potential, hydrostatic or turgor pressure

Facilitated Diffusion - Permeases


Active transport
pumps may be cotransport or uniport

Special pumps include

Na+ / K+ (especially in nerve cells)

H+ (mitochondria and chloroplasts relie on proton pumps)

Ca+2 (controls muscle contractions)

Endocytosis / Exocytosis (involves large membrane patches or domains)

Receptor mediated (clathrin and caveolae)



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