1. The Structure of the Plasma Membrane

2. Membrane Structure The plasma membrane is 8 nm thick. It is mainly made up of phospholipids and proteins.

3. Membrane Structure Phospholipid bilayer protein cholesterol c carbohydrate

4. Membrane phospholipids Phospholipids have a hydrophilic head and two hydrophobic tails.

5. Membrane phospholipids The phospholipids form a bilayer - The hydrophilic heads face outward and the hydrophobic tails face inward Hydrophobic tails

6. Membrane Proteins Membrane proteins are found within the phospholipid bilayer They can extend all the way through the bilayer – integral proteins They can be found embedded on either surface – peripheral proteins Integral Protein Phospholipid bilayer Peripheral protein

7. Functions of Membrane Proteins

8. Some proteins transport substances across the membrane by forming channels or by physically moving them across the membrane.

9. Membrane Proteins Functions of membrane proteins include: Transport of substances across the membrane Join cells to one another Act as enzymes Bind to chemical messengers from other cells Act as identification tags so cells can recognize one another Attach to cytoskeleton and the extracellular matrix

10. Membrane cholesterol and carbohydrates Cholesterol Cholesterol is found within the phospholipid bilayer It helps stabilize the phospholipids Carbohydrates Located on outer layer of membrane only Bound to proteins (glycoproteins) or phopholipids (glycolipids) Act as identification tags for cell cell recognition

11. Fluid Mosaic Model

12. The membrane is a fluid mosaic Fluid – the phospholipids and the proteins drift within the membrane Mosaic – the diversity of proteins found within the membrane and the arrangement of these proteins in the membrane

13. Lecture Review 11/28 1.What is the membrane mainly composed of? 2.How are the phospholipids arranged in the membrane? 3.What are the 2 types of membrane proteins and why are they different? 4.What is the role of cholesterol? 5.What is the role of carbohydrates? 6.What are 2 functions of the proteins in the membrane? 7.Why is the current model called fluid mosaic?