1. Cell Biology Overview Cell Membranes Cell Cycle and Specialization
Microscopes
Introduction / Cell Theory
Cellular Respiration
Cell Cycle and Specialization
Cell Division
Protein Synthesis

2. Cell Membranes Amoeba moving Cells Dividing
The cell membrane surrounds the cell and forms a boundary between the cell and its environment. It is fluid, flexible and dynamic.
The cell membrane changes shape as a cell moves. It divides in two when the cell divides.
So how does the cell membrane do this?
Amoeba moving
Cells
Dividing

3. The Cell Membrane’s role?
Cell Membrane Roles
Flexible Boundary
Platform for cell
recognition
communication
The cell membrane has three main roles in the life of a cell.
It forms a boundary, a fence around the cell
It controls what enters and leaves the cell
It serves as a platform for molecules used in cell-cell adhesion, recognition and signaling
Access Control

4. What makes these roles possible?
Cell Membrane Building Blocks
Phospholipids
Glycoproteins
Cholesterol
Glycolipids
Proteins
These roles are possible because of the molecules that make up the cell membrane.
Phospholipids and cholesterol made up most of the membrane, making it semi-permeable.
Proteins span the membrane and serve as channels for molecules entering and leaving the cell.
Glycoproteins and glycolipids are hybrid biomolecules (they are made of protein and glycogen or glycogen and lipids joined together) that provide glue for cells to attached to one another, serve as signatures identifying self from nonself and signal other cells in the body.
Flexible Boundary
Platform for
cell adhesion
cell recognition
cell communication
Controls access

5. Chemistry Reboot!!!

6. Phospholipids
Phospholipids are the most common molecules in the cell membrane. Each phospholipid molecule has a polar (hydrophilic) head and two nonpolar (hydrophobic) tails. The phospholipids are aligned tail to tail so a nonpolar area forms a hydrophobic region between the hydrophilic heads on the inner and outer surfaces of the membrane.
Cholesterol molecules are embedded among the phospholipids. The cholesterol molecules add rigidity to the layer. The cholesterol molecules keep the phospholipids from flying apart in warmer temperatures and they keep the membranes flexible at colder temperatures.

7. Cell Membrane Structure the fluid mosaic model
This diagram shows the molecules that make up a typical cell membrane.
Here are the phospholipids interspersed with cholesterol.
Proteins are embedded in the membrane as are glycoproteins
Glycolipids are anchored in the outer layer.