1. Cell Membrane

2. Cell Membrane and Homeostasis
Homeostasis is maintaining a stable internal environment within the cell
The cell membrane helps to do this by controlling what can cross into and out of the cell

3. Selectively Permeable
The cell membrane is selectively permeable, meaning that not everything can go across it.
Only certain things can get into the cell and only certain things can leave the cell

4. Structure
Cell membrane structure helps it regulate what can pass through and what can’t

5. Structure continued…
Phospholipids: special lipid (fat) molecule that has a phosphate head and two fatty acid tails
Phosphate head is polar (has a charge) and likes water
Hydrophilic
Fatty acid tails are nonpolar (doesn’t have a charge) and don’t like water
Hydrophobic

6. Structure continued…
These phospholipids form a double layer called a phospholipids bilayer with the phosphate groups on the outside and the fatty acid tails in the middle
This happens because there is water inside and outside of the cell, so the water loving phosphate end is always by the water

7. What can pass through the membrane?
This allows small, nonpolar substances to pass through because all other substances are repelled by the nonpolar fatty acids

8. The cell needs to let other things inside and out of the cell at certain times to its uses membrane proteins to allow specific things across the membrane at specific times.

9. Types of Membrane Proteins

10. Cell-Surface Proteins
Similar to a nametag
A chain of carbohydrates attached to the cell membrane to identify each type of cell
Ex: Heart cells have one type of sugar chain, while lung cells have another type of sugar chain
Attached to the cell membrane using glycoproteins
Glycoproteins can help cells work together

11. Receptor Proteins
Similar to you smelling, hearing, or touching your surroundings
Enable a cell to sense its surroundings by binding certain substances outside the cell
Allows the cell to react to its surroundings

12. Enzymes
Help with important chemical reactions inside the cell

13. Transport Proteins
Allows certain necessary substances that cannot pass through the cell membrane into and out of the cell