diffusion
spontaneous movement of a substance from 1 region to another, often w/ net movement from high conc. to low conc.
facilitated diffusion
passive transport of a substance across a membrane w/ assistance of transmembrane carrier proteins or channel proteins
carrier protein
specialized membrane proteins that change shape during the transport process
channel protein
enable ions or polar molecules to move across lipid bilayers efficiently in response to existing gradient
active transport
movement of ions/molecules across membrane against an electrochemical gradient
- requires energy & assistance of transport protein
- must counteract entropy ↓
protein models
(1) fluid mosaic model
(2) sandwich model
freeze-fracture electron microscopy
innovative technique for visualizing surface of plasma membranes
peripheral membrane protein
protein that binds to membrane w/out passing through & a protein does not span entire lipid bilayer & associates w/ only one side of bilayer
- some only found in interior cell
- others only found on exterior cell
- often attached to transmembrane proteins
- come off easily
integral membrane protein
protein that spans membrane & has segments facing both interior & exterior surfaces
- hydrophobic embedded part
- some transmembrane parts
aka. transmembrane protein
detergent
small amphipathic molecule used to solubilize hydrophobic molecules in aq. solution
electrochemical gradient
combo of ion’s [] gradient & electrical (charge) gradient across a membrane that affects ion diffusion across membrane
electrical + chemical -> diffusion
channel proteins
types of pores in cell membrane
- enable ions / polar molecules to move across lipid bilayer in response to existing gradient
- selective: permits particular types of ions or small molecules to pass through only
gated channel
channel protein that opens/closes in response to specific stimulus
(ie) aquaporin & ion channel
(ie) voltage & ligand gated
aquaporin
type of channel protein in which water moves cross plasma membrane over 10x faster than w/out aquaporin
“water-pores”
ion channel
specialized protein channel that allows certain ions to diffuse across plasma membrane down an electrochemical gradient
- form pores in membrane, which is where ions move through
passive transport
powered by diffusion along electrochemical gradient
- no need energy
- use gradients as force
(ie) facilitated diffusion
secondary active transport
gradient set up by pump provides energy required to pwr movement of diff. molecule against its particular gradient
- link passive to active
- glucose movement in small intestine against [] gradient
- Na+ down gradient, glucose against gradient
- no ATP
aka. cotransport
pump
protein membrane that can:
(1) hydrolyze ATP
(2) change shape
(3) pwr active transport of specific ion/small molecule across plasma membrane against electrochemical gradient
- independent of gradients
primary active transport
critical for membrane potential
channel fcn
(1) passive transport
(2) facilitated diffusion
(3) electrochemical gradient
carrier protein fcn
(1) passive transport
(2) facilitated diffusion
(3) electrochemical gradient
voltage gated
charge (+/-) depends on open/close
ligand gated
depends on if ligand (binds to receptor) is on channel or not
membrane-associated proteins
(1) peripheral membrane protein
(2) integral membrane protein
(3) glycoprotein
