The slides below are about a cell membrane. They define a cell membrane and also discuss how molecules moves in and out of the cell membrane using different channels.

1. CELL MEMBRANE

2. A CELL MEMBRANE IS:
• The boundary that separates the living cells from its surrounding and controls the movements
into and out of the cell it surrounds.
• it allows selective permeability. This means that it does not allow everything to enter nor leave
the cell.

3. What makes a membrane
-Membranes are made up of Lipids, Proteins and other
macromolecules.
-The most abundant lipids in most membranes are phospholipids.
-Phospholipid is an amphipathic molecule. Meaning it has both a
hydrophilic part and a hydrophobic region.

4. Phospholipids
-They are made up of fatty acid tails and these fatty acid tails are hydrophobic. This means that
they do not mix with water.
-Their heads are made up of phosphate group which are hydrophilic. This means that they mix
with water.
PHOSPHATE
FATTY ACID TAIL

5. Proteins
-Proteins determines a membranes specific function. Therefore the proteins that makes up a cell
membrane and a protein that makes up a membrane of an organelle are different.
Peripheral proteins.
-Loosely bound to the surface of the membrane.
Integral proteins.
-They penetrate the bilayer of the cell membrane
-They are transmembrane protein.

6. Below is a picture of how a channel protein looks like
https://tinyurl.com/yddz7efr

7. Passing through a membrane
1. PASSIVE TRANSPORT.
• Simple diffusion
-diffusion of nonpolar molecules, hydrophobic molecules such as fats.
• Facilitated transport.
-diffusion of polar molecules, hydrophilic molecules using a protein channel.
2. ACTIVE TRANSPORT
-Uses protein pump.
-Requires energy (ATP)

8. Summary of diffusion through a membrane

9. Moving large molecules
1. Endocytosis
Phagocytosis- Cellular intake of food.
Pinocytosis-Cellular intake of liquid
2. Exocytosis

10. References
Bester, M. et al. (2013). Platinum: Natural Sciences. Cape Town: CTP Printers.
Dschreiber44. (2009). Cell membrane. Available from slideshare at
https://www.slideshare.net/dschreiber44/cell-membrane
Foley, T. (2011). Cell membrane and transport. Available from slideshare at
https://www.slideshare.net/ToniFoley/24-cell-membrane-and-transport
Ravagnan, M. (2012). PowerPoint cell membrane transport copy. Available from slideshare at
https://tinyurl.com/ybxa5xvz
Saikia, A. (2018). Transport across the cell membrane. Available from slideshare at
https://www.slideshare.net/AnkurSaikia3/transport-across-the-cell-membrane