2. The Cell Membrane

3. The cell membrane is a fluid structure that forms a boundary between the cell the outside environment. Inside Outside Cell membrane

4. Building a membrane How do you build a barrier that keeps the watery contents of the cell separate from the watery environment? What substance do you know that doesn’t mix with water?  FATS   LIPIDS  Remember: oil & water don’t mix!!

5. The cell membrane is composed of phospholipids. phosphate “head” lipid “tail” Polar attracted to water Nonpolar repels water A phospholipid is composed of two parts: A head – phospate & glycerol Two tails - two fatty acids

6. The phospholipids are arranged in a double layer called a phospholipid bilayer. 1 2 bi-layer

7. Nonpolar --oily-- polar Inside Cell Outside Cell The polar “heads” are arranged along the outside interacting with water both inside and outside the cell. H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O

8. Function: to regulate/control which substances enter and leave the cell. cells need materials in & products or waste out IN Food Glucose O 2 H 2 O OUT Waste Hormone CO 2 H 2 O

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10. The cell membrane practices selective permeability by only allowing certain substances to enter and exit.

11. InsideCell Outside Cell H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O So what needs to get across the membrane? aa H2OH2O sugar lipids salt waste O2O2

12. The cell membrane also contains other molecules embedded within the phospholipids layers. Molecules like cholesterol and proteins Cholesterol strengthens cell membrane

13. Proteins Proteins that: Create channels for specific substances to pass. Transport specific substances across membrane. Recognize specific signals so cell can communicate with other cells. Identification tags enabling cells to distinguish one type of cell from another.

14. Create channels for specific substances to pass. Recognize specific signals so cell can communicate with other cells. Identification tags enabling cells to distinguish one type of cell from another. Transport specific substances across cell membrane.

15. The Cell Membrane with Membrane Proteins