1. The Cell Membrane 3.3
E.Q.: How is the structure of the cell membrane important for its function?

2. Cell Membrane Function
Forms a boundary between inside & outside of cell
Controls what goes in & out of cell

3. The cell membrane is selectively permeable meaning that it allows some things to pass through but not others
This helps the cell maintain homeostasis

4. Cell Membrane Structure
Consist of a phospholipid bilayer
Phospholipids are composed of three parts: 1. a charged phosphate group
2. glycerol
3. two fatty acid chains
Phospholipids have a polar hydrophilic head (phosphate group) & nonpolar hydrophobic tails (fatty acids)

5. Phospholipid
Phospholipid

6. Cell membrane
Phospholipid bilayer

7. Other molecules in membrane:
Cholesterol: strengthen the cell membrane
Proteins: help materials cross the membrane and make up cytoskeleton
Carbohydrates: identification tag for cell

8. carbohydrates
protein
cholesterol
protein
protein

9. Scientists use the fluid mosaic model to describe the cell membrane because
1. membrane is flexible
2. membrane contains a variety of
molecules

10. Chemical signals are transmitted across the cell membrane via receptors.
Receptor: protein that detects a signal & performs an action in response
Receptors bind with a molecule called a ligand and the two change shape

11. Two types of Receptors:
1. Intracellular receptor: receptor located inside the cell
-small molecules such as some hormones are able to cross the cell membrane and bind to intracellular receptors

12. 2. Membrane receptor: receptor located within cell membrane
-molecules that can’t pass through membrane bind to these receptors with send signals to the inside of the cell