Cell membranes

Page
4

The membrane is 7nm thick on average.

Some phospholipids have carbohydrates attached to them – GLYCOLIPIDS

Some of the proteins have carbohydrates attached to them – GLYCOPROTEINS

The membrane also contains molecules of CHOLESTEROL

Slide 20

Roles of components of cell membranes

Using the following headings produce a table on A4 to summarise roles of t he

different types of molecules found in the cell membrane. Try not to copy, pick

out the relevant information and write it in note form You may want to use

bullet points, different coloured pens etc basically whatever helps you to remember them.

There will be a short test on this next lesson! Use pages 53-54.

Component Function

Phospholipids

Cholesterol

Proteins

Glycolipids and Glycoproteins

Slide 21

Summary

Cell membranes have a basic structure composed of a PHOSPHOLIPID BILAYER.

Phospholipds have HYDROPHOBIC (non-polar) tails and HYDROPHILIC (polar) heads.

The best model of the cell membrane is called the FLUID MOSAIC MODEL

The average thickness of the membrane is 7nm.

The fatty acid tails of phospholipids can be SATURATED (straight) or UNSATURATED (bent)

Proteins can float or be fixed and also have hydrophobic and hydrophilic portions.

Some proteins and phospholipids have carbohydrates attached to them to form GLYCOPROTEINS AND GLYCOLIPIDS.

Phospholipids form the bilayer, act as barrier to most water soluble substances

Cholesterol regulates the fluidity of the membrane, gives mechanical stability and help to prevent ions from passing through the membrane.

Proteins act as transport proteins to act as channels for substances to move into or out of the cell. Some act as membrane enzymes and some have important roles in membranes of organelles.

Glycolipids and Glycoproteins help to stabilise membrane structure, some act as receptor molecules eg for hormones and neurotransmitters or as antigens for other cells to recognise them.

Slide 22

Movement of selected molecules across the cell membrane

Slide 23

Moving amoeba