FUNCTIONS & TYPES OF CELL FUNCTIONS & TYPES OF CELL MEMBRANE PROTEINSMEMBRANE PROTEINS

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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 PROTEINSb) 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    In Integral membrane proteins are typically hydrophilic where they interact with the hydrophilic portion of the membrane and overlying (and underlying) H2O

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).