7: Membrane proteins and osmosis and diffusion

Name3 types of membrane proteins

Transport proteins

2. Receptor Proteins

3. Recognition proteins

Recognition proteins?

Serve as identification tags for cells of the immune system. Immune cells recognise cells as self or non-self and protect against foreign bodies by triggering the immune system.

Receptor proteins?

Cells must respond to changes in their environment.

Cells have receptors that detect signals and initiate reaction/cascade.

Different receptors are specific for different molecules

How do receptor proteins carry out their function?

A receptor protein has a shape that fits a specific messenger molecule, such as a hormone.

The messenger molecule (hormone) binds to its receptor protein in membrane of target cell.

This leads to activation of enzymes or genes in a cell

Once a signal reaches its target molecule (usually a protein), it works to changethebehaviourofthecell.

Depending on the signalling molecules involved, the cell can respond in a varietyofways.

Solute?

Solvent?

Solution?

Substance dissolved in a liquid

Liquid dissolves a solute

Solute dissolved in a solvent

Concentration gradient?

The difference in the concentration of a substance between two areas.

The bigger the difference, the steeper the concentration gradient and the faster the molecules of a substance will diffuse.

Diffusion across cellmembrane

Facilitated diffusion is diffusion of polar molecules and ions with the help of transport proteins.  Transport proteins may have shapes specific to the molecule requiring transport.

Tonicity?

Tonicity is a measure of the potential of 2 solutions separated by a semi permeable membrane

Hypotonic?

a solution has a lower concentration of solute

Hypertonic

solution has a higher concentration of solute

Isotonic?

solution has the same concentration of solute

Osmosis?

 Osmosis is the movement of water membrane molecules across a semi-permeable from an area of low solute concentration, to an area of high solute concentration

Osmosis in plants?

Vacuole of plant cell is full of cell sap (rich in sugars and salts). It is therefore Hypertonic compared to Soil Water. Therefore: Water enters root hair from soil by osmosis

Paramecium spp

 The Paramecium cell membrane is less permeable to water than other animal membranes.  Nonetheless, water gradually passes and accumulates into the cell.  The Paramecium has a contractile vacuole that functions as a bilge pump to evacuate water periodically