6. Plamsa Membrane Flashcards
What is the fluid mosaic model?
Whereby plasma membrane is a mosaic of coumpounds, phospoholipds/cholesterol/proteins that cab move freely and fluidly in the plane of the membrane- dynamic- phospholipids and proteins contiguous sliding past one another
Describe structure of pm
Known as lipid bilayer
Houses associated integrated/peripheral proteins
Inner layer faces cytoplasm - outer faces ect
Phospholipid - lipid made of glycerol/two fatty acid cahins and phosphate group- p bilayer
Describe carbohydrate groups in pm
Only present on outer surface of pm
Attached to proteins - glycoproteins
Lipids- glycolipids
Function of pm?
1- envelops the cell- maintains its structure and functional integrity
2- acts as semipermeable membrane between cytoplasm and ecf- controls transport
3- excludes unwanted materials from entering cell- forms physical barrier to enviroment
4- maintains ionic con and osmotic pressure of cytosol
5- forms contact with neighbouring cells
Permeability of bilayer
To small, lipid soluble non polar molecules
Water
Describe membrane lipids
Ampipathic- both hydrophilic and hydrophobic reigons
3 main types of membrane lipids
Phophoglyercides, sphingolipids. Cholesterol
What are the four major phospholipids present in pm
Phosphatidyl- choline/ ethanolamine/serine/sphingomyelin
Describe phosphoglycerides
Head group
Phosphate
Glycerol backbone
Fatty acid tails
Diglycerides - Only 20h groups of glycerol are esterefied
Describe sphingolipids
Derivatives of sphingosine - an amino alcohol containing long hydrocarbon chain
Cholesterol
Amphipathic - small hydrophilic hydroxyl group towards membrabe surface- hydrophobic = embedded in bilayer
What are the three main categories of pm
Integral/ transmembrane
Peripheral
Lipid anchored
Protein attactched
Describe integral protein types
A- helix- recognition/receptors
Helical bundles- enzymes/transporters/receptors
B barrel- transporters- channel proteins
Peripheral proteins types
Anchores - integrins
