Topic 3 Flashcards
Phospholipids are amphipathic moleciules
containing hydrophopic and hydrophilic regions
Fluid mosaic model
a membrane is a fluid structure with a “mosaic” of proteins embedded in it
Larry Fry and Michael Edidin
differentially labelled membrane proteins of mouse and human cells
Membrane fluidity
affects the permeability of the membrane and the function of its proteins
Affect the fluidity of a membrane
Temperature
Fatty acid tails (longer=more viscous
shorter=fluid
Sterols Regulate Membrane Fluidity
Animal cells insert cholesterol into bilayer Prevent freezing by stopping phospholipids from packing to tightly
Prevent melting by restraining phospholipid movent
peripheral proteins
bound to the surface of the membrane
integral proteins
penetrate the hydrophopic core and are embedded in membrane
Transmembrane proteins
Integral proteins that span membrane
Six major functions of membrane proteins
1) transport
2) enzymes
3) signalling
4) cell - cell recognition
5) intercellular joining
6) anchoring
Two types of transport
Passive: based entirely on diffusion (moves down/with a concentration gradient
Active: Requires energy (Moves up/against a concentration gradient
Tonicity
the ability of a surrounding solution to cause cells to gain or lose water
isotonic solution
Solute concentration is the same as that inside the cell; no net water movement across the plasma membrane
hypertonic solution
solute concentration is greater than inside the cell; cell loses water
hypotonic solution
solute concentration is greater than inside the cell; cell gain water
carrier proteins
undergo subtle change in shape (conformation) that translocate the solute binding site across the membrane
Aquaporins
allow water to move across the membrane at rates that can sustain life
faciltated difussion
the solute moves down its concentration gradient and transport requires no energy
active transport
moves substances against their concentration gradients
The sodium-Potassium
a specific case of active transport
Membrane potential
the voltage difference across a membrane
Cotransport
occurs when active transport of a solute indirectly drives transport of other solutes
Large molecules, such as polysaccharides and proteins, cross membrane via…
vesicles (Bulk transport)
Exocytosis
transport vesicles migrate to the membrane, fuse with it, and release their contents to the outside of
Endocytosis
The cell takes in macromolecules by forming vesicles from the plasma membrane
