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THE PLASMA MEMBRANE
Transcript of THE PLASMA MEMBRANE
Regulates what enters and leaves the cell
PLASMA MEMBRANE CONSTITUENTS
a phospholipid bilayer
cholesterol (only in animal cells, that serves as a "glue" to give rigidity to the fluid composition of the phospholipids)
Phospholipids forming the bilayer: small, non-polar substances will fit through the pores in this bilayer moving in or out of the cell.
Recognition proteins or Glycoproteins: their carbohydrates work as tags on the outer surface of the plasma membrane, allowing cells to recognize themselves as belonging or not belonging.
Receptor proteins: proteins on the surface of the plasma membrane to which chemical messengers are attached to give instructions to which the cell will respond
Channel proteins: allowing the movement of small, charged particles through the plasma membrane, substances such as different ions, Na+, K+, etc.
Carrier proteins: allowing bigger substances, but still monomers (bigger stuff needs to be digested) to move through the cell
Could be others, but as mentioned before, they are attached to the proteins in order for the cells to recognize themselves as belonging to the same tissue.
Better known as antigens in the cell which work for example with our immune system.
SELECTIVITY OF THE PLASMA MEMBRANE
The plasma membrane is said to be selective, this as a door keeper. It will allow only certain substances to move into or out of the cell.
This is achieved by:
Either following their gradient (from where there is a bigger amount of that substance towards where there is a lesser amount of it, without the use of ENERGY FROM THE CELL.
Kinetic energy will always be needed
since we are talking about moving things
Kinetic refers to movement
SELECTIVITY OF THE PLASMA MEMBRANE (2)
Or, against the gradient (from where there is a lower concentration of a substance, towards where there is a higher concentration of it, using ENERGY IN THE FORM OF ATP FROM THE CELL.
VESICLE MEDIATED TRANSPORT
THE PLASMA MEMBRANE
FUNCTIONS, COMPOSITION AND, TRANSPORT MECHANISMS