Key Terms
Membrane thickness
5 to 10 nm. For scale, a red blood cell is about 8 micrometers wide - roughly 1,000 times wider than the membrane itself
Structure
Glycerol backbone + two fatty acid tails (carbons 1 and 2) + phosphate-containing head group (carbon 3).
Chain length
2-60 monosaccharide units; can be straight or branched.
Simple diffusion
A substance moves from high to low concentration until evenly distributed. That endpoint is called dynamic equilibrium -
Think of it this way
More solutes dissolved in water = less free water in that solution. Water moves toward the more concentrated solution (t
Osmolarity
Total solute concentration in a solution
Six-step cycle
1. Pump faces interior; high affinity for Na+; three Na+ bind 2.
Result
More Na+ outside, more K+ inside, and the interior is slightly more negative than the exterior. The pump is electrogenic
Also
The hydrogen ion gradient in mitochondria works this way. H+ ions pumped across the inner membrane by primary active tra
Examples
Neurotransmitter release from synaptic vesicles; secretion of extracellular matrix proteins; waste removal.
Amphiphilic
Having both a hydrophilic (polar) and a hydrophobic (nonpolar) region; describes phospholipids and integral proteins
Aquaporin
Channel protein that allows water to pass at very high rate
Carrier protein
Membrane protein that binds a substance and changes shape to move it across; specific to one substance; can become satur
Caveolin
Protein that coats the cytoplasmic side of the membrane during potocytosis; analogous to clathrin
Channel protein
Membrane protein with a hollow hydrophilic core; allows specific substances to pass; much faster than carrier proteins