LECTURE 4 Flashcards
Plasma membranes are
Selectively permeable
What is the basic structure of all biological membranes
Spherical phospholipid bilayer
Membranes are made of
Proteins and lipids
Fluid mosaic model
Membrane is a fluid structure with a ‘mosaic’ appearance cuz of different types of proteins in it.
Proteins in the bilayer can be classified in two groups
1) integral
2) peripheral
Integral proteins
Embedded in the bilayer, at least one portion of the protein is hydrophobic
Peripheral proteins
Attached loosely to the surface of the membrane
Membranes consign other components:
- glycoproteins
- Glycolipids
- cholesterol
Glycoproteins
- membrane proteins that have a sugar attached
- important function in cell recognition.
Glycolipids
membrane lipids that have a sugar attached
Cholesterol
- inserts between phospholipid molecules.
- influences membrane permeability and fluidity.
Biological membranes are fluid at
physiological temps
Phospholipids are able to move _______ but rarely ever move _______
Laterally Transversely
High temps increase
Fluidity in membranes
At higher temps, the membrane becomes more
Permeable
Is the temp is low enough, the membrane will turn
Solid (phase transition)
Length of fatty acids in the phospholipids
Short chains have less stable interaction then long Chains. Therefore, lower temp required to make short chain into solids.
What is the shape of fatty acids in the phospholipids influenced by
double bonds,
Unsaturated fatty acids in phospholipids
Double bonds cause structural kinks, decreasing ability of chains to pack together
How does Cholesterol maintain membrane fluidity
Fluidity buffer at a greater range of temps
What does cholosterol interfere with
Lateral movement of phospholipids, causing a reduction in ,embrace fluidity at moderate temps.
What does cholosterol prevent
Close packing of phospholipids at low temps, (solidification)
Animals have _____ of cholesterol and plants have ________ cholesterol in their membranes
A lot. Little
Six major function of membrane proteins
1) transport of molecules in or out of cells
2) enzymatic reactions near the membrane
3) signalling via receptors
4) c ell-cell recognition
5) intercellular attachment
6) attachment of the extra cellular matrix proteins
