1. The Cell Membrane

2. The Cell Membrane Aka. Plasma Membrane
It is responsible for controlling what enters and exits the cell.
Ex. Materials like glucose must enter the cell, and waste materials must exit the cell.

3. The Cell Membrane Is described as the Fluid Mosaic Model
“Fluid” because molecules that make up the membrane are free to move around
“Mosaic” made up of different molecules all working together

4. The Cell Membrane Composed of a phospholipid bilayer
Double layer of phospholipid molecules

5. The Cell Membrane Phosphate Group Fatty Acid Hydrophilic “head”
Outside Cell
Phosphate Group
Hydrophilic “head”
Water loving
Point towards the inside and outside of the cell
Are in contact with the intra- and extra- cellular fluid
Fatty Acid
Hydrophobic “tails”
Water fearing
They point towards each other and away from the watery environment
Inside Cell

6. The Cell Membrane
Cell membrane is semi-permeable/selectively permeable
Only certain materials are allowed to pass through
Other molecules associated with cell membrane:
Steroids (i.e. cholesterol)
Proteins

7. The Cell Membrane Cholesterol A lipid (steroid)
Found in between phospholipids
Act as membrane stabilizers
help maintain the fluid condition of the bilayer by preventing fatty acids from associating

8. The Cell Membrane Proteins
Can be divided into four major categories according to the function of the protein:
1) Transport Proteins - protein “channels” that help substances pass through the membrane
2) Enzymes – some enzymes can be associated with the membrane (ex. enzymes of photosynthesis and cellular respiration)

9. The Cell Membrane
3) Signalling Proteins – bind specific chemicals (ex. hormones) and this binding triggers changes on the inner surface of the membrane triggering a cascade of reactions in the cell
4) Attachment and Recognition Proteins – act as attachment points for cytoskeleton elements (structural support) / can function in cell-cell recognition (ex. immune cell recognizing invader)

10. Functions of Membrane Proteins

11. The Cell Membrane Proteins
Can also be divided based on location within membrane:
1) Integral Proteins
- embedded in the lipid bilayer
Most integral proteins are transmembrane proteins (meaning they span the entire membrane)
2) Peripheral Protein
Found on the surface off the membrane
Can be attached to integral proteins

12. The Cell Membrane