1. The Key to Cellular Transport
The Cell Membrane
The Key to Cellular Transport

2. Characteristics of the Cell Membrane
Made of phospholipids
– arranged in two layers called a bilayer
Selectively permeable
-it controls “selects” what can enter or leave the cell
-some materials are allowed through others aren’t
Fluid Mosaic Model
- made of different molecules – phospholipids, proteins,
cholesterol
- the molecules aren’t static but can move “fluid”

3. Lipid bi-layer – the heart of the membrane
Phospholipids are arranged into 2 layers
- called a bilayer

4. Phospholipids: Phosphate Heads
Polar/hydrophillic – attracted to water and charged particles

5. Phospholipids: Lipid Tails
Nonpolar/hydrophobic – repel water and charged particles

6. Cholesterol Found in bilayer – helps to hold the membrane together
while adding to fluidity of the membrane
Amount of cholesterol varies depending on the amount of fluidity needed in a membrane. Ranges from 25% of total lipid to 0%

7. Glycoproteins
Proteins with carbohydrates attached – identifies the cell type
-allows it to bind with other cells of the same type
The carbohydrates are oligosaccharides (chains of no more 15 monosaccharides) Glycoproteins also are responsible for cell adhesion. Two cells with matching glycoproteins will bind together – allows the creation of tissues. Glycolipids exist as well they serve as recognition signals for cell interactions. The carbohydrate of glycolipids in cancer cells change. This signals to white blood cells that the cell needs to be destroyed

8. Receptor Proteins
recognize and bind with substances outside of the cell,
causing changes inside the cell

9. Enzymes
Allow reactions to occur- light reactions and ETS occur with enzymes in membrane

10. Transport Proteins
Proteins that extend across the membrane – provide a way for large or charged molecules to cross the membrane

11. Types of Transport Proteins
Ion Channels- allow certain charged particles to cross the membrane – passive transport
Carrier Proteins – bind to a specific molecule and carry it
across the membrane
- facilitated diffusion – proteins carry molecules with the concentration gradient /no cellular energy is required
- active transport – proteins carry molecules against the concentration gradient/ cellular energy is required