Structure If The Cell Surface Membrane Flashcards
what is the plasma membrane?
-all members around and within all cells have that same basic structure
what is a cell surface plasma membrane?
-the name given to the plasma membrane that surrounds cells and forms the boundary between the cell cytoplasm and the environment allowing different conditions to be established inside and outside of the cell
what are phospholipids?
-they are important components of the cell surface membrane
Why are phospholipids important?
- the hydrophilic heads of both phospholipid layers point to the outside of the cell surface membrane attracted by water on both sides
- the hydrophobic tails of both phospholipid layers point to the centre of the cell membrane repelled by the water on both sides
What moves through the membrane via phospholipid portion?
-lipid soluble material
what is the function of phospholipids in the membrane?
- allow lipid soluble substances to enter and leave the cell
- prevent water soluble substances entering and leaving the cell
- make the membrane flexible and self sealing
where are proteins found in the phospholipid bilayer?
-proteins are interspersed throughout the cell surface membrane and embedded in the phospholipid bilayer as cell receptors, protein channels or carrier proteins
what are extrinsic proteins?
- proteins that occur in the surface D the bilayer and never extend completely across
- they act to give mechanical support to the membrane or work with glycolipids as cell receptors for molecules like hormones
what are channel proteins?
- they span the phospholipid bilayer from one side to the other
- they form water filled tubes to allow water soluble ions to diffuse across the membrane
what are carrier proteins?
- they span the phospholipid bilayer from one side to the other
- they bind to ions or molecule like glucose then change shape in order to move these molecules across the membrane
what are the functions of proteins in the membrane?
- they provide structural support
- act as channels transporting water so blunt substances across the membrane
- allow active transport across the membrane through carrier proteins
- form cell surface receptor se for identifying cells
- helps cells adhere together
- act as receptors
what is cholesterol?
-cholesterol molecules occur within the phospholipid bilayer of the cell surface membrane
what is the function of cholesterol in the membrane?
- reduce lateral movement of other molecules like phospholipids
- make the membrane less fluid at high temperatures
- prevents leakage of water and dissolved ions from the cell
what are glycolipids made from?
- a carbohydrate covalent bonded with a lipid
- the carbohydrate portion extends from the phospholipid bilayer into the watery environment outside the cell where it acts as a cell surface receptor for specific chemicals
what are the functions of glycolipids in the membrane?
- act as recognition sites
- helps maintain the stability of the membrane
- helps cells to attach to one another and so form tissues
what are glycoproteins?
- carbohydrate chains that are attached to many extrinsic proteins on the outer surface of the cell membrane
- they act as cell surface receptors from hormones and neurotransmitters
what are the functions of glycoproteins?
- act as recognition sites
- helps cells to attach to one another and so form tissues
- allows cells to recognise one another like lymphocytes can recognise own cells
What does the cell surface membrane do?
-controls the movement of substances into and out of the cell
Which molecules can’t diffuse freely across the cell surface membrane?
- molecules that aren’t soluble in lipids
- large molecules that can’t pass through the channels in the membrane
- molecules of the same charge as the protein channels are repelled
- electrically charged Polar molecules can’t pass through the non polar tails of the bilayer
what is the fluid mosaic model?
-the way in which all the various molecules are combined into the structure of the cell surface membrane
how is the fluid mosaic model fluid?
-the individual phospholipid molecules can move relative to one another which gives the membrane a flexible structure that is constantly changing shape
how is the fluid mosaic model a mosaic?
-the proteins are embedded in the phospholipid bilayer vary in shape size and pattern in the same way as the stones or tiles of a mosaic
What do cholesterol molecules do?
- they add strength to the membranes
- they are very hydrophobic so prevent loss of water and dissolved ions from the cell
- they pull together the fatty acid tails of the phospholipid molecules which limits their movement and that of other molecules without making the membrane too ridged
