2. Objectives
• Understand the characters of the fluid mosaic model
• Understand how the structure of phospholipid determine the
structure of the cell membrane
• Recognize different type of membrane protein and their function
• Understand the structure and function of glycoprotein on cell
membrane
3. Cell membrane
• Composition
• Phospholipid
• Protein
• Saccharide
• Fluid mosaic model
• Functions
• Movement of molecules across the cell membrane
• Passive transport (diffusion – free/facilitated, osmosis)
• Active transport (membrane transport protein, endocytosis, exocytosis)
4. The cell membrane
• A.k.a plasma membrane
• Separate the cell from the outside
world
• Consists of:
• Phospholipid: form a sheet where other
molecules attach to
• Protein: forms channels for ions and
other molecules, receptors, antigen
presentation (for the immune system),
adhesion
• Cholesterol: regulates membrane
fluidity, protein anchoring
• Saccharide: (as glycoprotein or
glycolipid) cell adhesion, cell recognition,
receptors
5. Quiz
• What is the function of cholesterol in the cell membrane?
a. To make the center of the membrane hydrophilic
b. To make the center of the membrane hydrophobic
c. To maintain the fluidity of the cell membrane
d. To act as an identification marker for the cell
6. Quiz
• Which of the following is NOT a component of the cell membrane?
a. 1. Phospholipids
b. 2. Cholesterol
c. 3. Nucleic acids
d. 4. Proteins
7. Conclusion
• Cell membrane is consist of phospholipid, protein (forms channels for
ions and other molecules, receptors), cholesterol (regulates
membrane fluidity) and saccharide (cell recognition, receptors)
At high temperatures, cholesterol stabilizes the membrane and raises its melting point, whereas at low temperatures it intercalates between the phospholipids and prevents them from clustering together and stiffening.
Pearson Biology figure 6,7
