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The Cell Membrane

Looks at the composition of the cell membrane - the Fluid Mosaic Model.

Ted Mitchell

on 15 February 2012

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Transcript of The Cell Membrane

The Cell Membrane
Fluid Mosaic Model

It is approximately eight nanometres wide. (1nm = 0.000000001m)

Q. What does this mean in real terms?

A. 12000 cell membranes = thickness of 1 piece of paper - that's THIN!

Distinguish the cell from its external environment.
Control the movement of substances into and out of the cell.
Enable cells to recognise each other and also identify substances, for example hormones.
Facilitate attachment of the cell’s cytoskeleton.
Provides surface area for chemical activity.
What does the cell membrane do?
It has three types of protein molecules embedded in its phospholipid layers:

structural (peripheral + integral)
receptor proteins, with carbohydrates attached to identify other cells (= glycoproteins).
How thin is it?
What does it consist of?
Let's look at the phospholipid bi-layer first
What about the protein?
Phospholipid (mostly)
some cholesterol and steroids
glycolipids and glycoproteins
So why is it called 'Fluid Mosaic'?
Fluid = constantly changing shape and composition

Mosaic = phospholipid molecules have various proteins, carbohydrates embedded within it forming something of a mosaic appearance.
Two main types of Transport;
Passive Transport
Active Transport
Passive Transport
Requires no use of energy
Movement with a concentration gradient
From High to Low
Osmosis and Dialysis are specific forms
of diffusion
Active Transport
Movement requiring energy (uses ATP)
Often against a concentration gradient
Low to High
Exocytosis Pinocytosis
Endocytosis Phagocytosis
Types of Solutions
Isotonic - Equal concentration of solutes outside
and inside the cell.
No Net movement of Water
Hypotonic - Less solutes outside cell, More solutes
inside cell.
Water wants to move inside cell.
Cell swells or possibly even ruptures.
Hypertonic - More solutes outside cell, Less solutes
inside cell.
Water wants to move outside cell.
Cell shrivels.
Full transcript