1. Cell Membrane Structure and Function Inquiry Into Life Chapter 4

2. The Fluid Mosaic Model The plasma membrane separates the internal environment of the cell from its surroundings. The plasma membrane is a phospholipid bilayer with embedded proteins. The plasma membrane has a fluid consistency and a mosaic pattern of embedded proteins.

3. The Fluid Mosaic Model The inside of the cell is mostly water – this is called intracellular fluid the outside of the cell is also mostly water – this is called extracellular fluid

4. The Fluid Mosaic Model Hydrophilic (water-loving) polar heads of the phospholipid molecules lie on the outward- facing surfaces of the plasma membrane. Hydrophobic (water-fearing) nonpolar tails extend to the interior of the plasma membrane.

5. The Fluid Mosaic Model

6. Cell Structures The cell membrane has two types of proteins throughout its structure: – Integral proteins: a protein that extends all the way through the plasma membrane.

7. Cell Structures The cell membrane has two types of proteins throughout its structure: – Peripheral proteins: a protein that lies close to one surface or the other, but does not extend through the plasma membrane.

8. Cell Structures Plasma membranes also contain cholesterol: – Cholesterol is made of lipids that are found in animal plasma membranes. It is related to steroids found in plants. – Its function is to strengthen the membrane by making it more rigid.

9. Cell Structures Carbohydrate chains make up two important structures in cells. – Glycolipids: phospholipids that have carbohydrate chains attached. – Glycoproteins: proteins that have carbohydrate chains attached.

10. Cell Structures Carbohydrate chains occur only on the exterior surface of the plasma membrane.

12. Integral Proteins - Transport Channel proteins: – A channel through which molecules move freely in and out of the cell. – Movement through these channels needs no ATP.

13. Integral Proteins - Transport Carrier proteins: – These proteins combine with the molecules, change their shape, and carry the molecule in or out of the cell. – This process needs ATP.

14. Integral Proteins - Marker Cell recognition proteins: – They act as ID tags, fingerprints or markers – “sugar coated” – each has a carbohydrate chain that is unique to it

15. Integral Proteins - Reactions Receptor proteins: – They have a special lock shape that allows certain molecules to fit into them like a key – This triggers a chemical reaction to occur within the cell.

16. Integral Proteins - Reactions Enzymatic proteins: – They also have a lock and key model. – They allow chemical reactions to happen faster inside the cell.

17. Peripheral Proteins These proteins play a structural role in the plasma membrane by giving it shape and strength. Cytoskeletal filaments are often found attached to these proteins.