FUNCTIONS & TYPES OF CELL MEMBRANE PROTEINS ECE UYGUR 9-C 37045

There are many types of membrane protein and these vary from cell type to cell type. It is important to remember that they can move around the cell membrane due to the fluid nature of the whole structure. They do not sit in one place but can move to where their function is required.

TYPES OF CELL MEMBRANE Poteins are typically associated with cell membranes. These proteins have numerous functions but may be divided structurally into two types. a) INTEGRAL MEMBRANE PROTEINS b)PERIPHERAL MEMBRANE PROTEINS

INTEGRAL MEMBRANE PROTEINS These are fully incorporated into the membrane and are in contact with both the inside and the outside of the cell. They are forms integral part of the membrane and requires harsh treatment for isolation. E.g.transmembrane proteins.

Integral membrane proteins span the lipid bayer at least a little Some integral membrane proteins completely span the lipid bayer Integral membrane proteins are typically hydrophobic where they interact with the hydrophobic portion of the membrane hydrophobic membrane In In tegral membrane proteins are typically hydrophilic where they interact with the hydrophilic portion of the membrane and overlying (and underlying) H 2 O hydrophilic H 2 O

PERIPHERAL MEMBRANE PROTEINS These are only assosicated with the outer of the bilipid layers and made contact with the extracellular space. They are fairly easy to isolate, thorough simple manipulation of salt concentrations.

INNER MEMBRANE PROTEINS These are only associated with the inner of the bilipid layers and make contact with the cytoplasm.

TRANSMEMBRANE PROTEINS  These are similar to integral proteins but appear to possess a channel connecting the extracellular space to the cytoplasm. They are extend across the lipid blayer a)Single-pass b) multi- pass

THE VARIOUS FUNCTIONS OF MEMBRANE PROTEINS CAN BE 1)To attach parts of the cytoskeleton to the cell membrane in order to provide shape. 2)To attach cells to an extracellular matrix in grouping cells together to form tissues.

3) To act as receptors for the various chemical messages which pass btw. Cells such as nerve impulses and hormone activity. 4) To take part in enzyme activity which can be important in the metabolism or as part of the body’s defence mechanisms.

To transport molecules into and out of cells by such methods as iomn pumps, channel proteins and carrier proteins. (these mechanisms will be explored in detail later in the course and are of some importance in understanding how some drugs and medicines act upon the body).