Plasma Membrane 2

Question 1

What are the different types of attachment for membrane proteins ?

Answer 1

Transmembrane - α-helical and β-barrel
Leaflet associated
Lipid linked
Protein attached

Question 2

What are the different classes of membrane proteins ?

Answer 2

Transporters
Linkers
Receptors
Enzymes

Question 3

How do plasma membrane proteins move ?

Answer 3

Plasma Membrane Proteins Move Laterally in Lipid Bilayer

Question 4

Describe different ways in which protein movement can be restricted ?

Answer 4

Inside tethering - tethered to cytoplasmic proteins like spectrin
Outside tethering - tethered to extracellular matrix
Cell-cell tethering - desmosomes
Cell polarity - epithelial tight junctions

Question 5

What is the glycocalyx ?

Answer 5

The glycocalyx is a dense, gel-like layer that surrounds the plasma membrane
It consists of glycoproteins, glycolipids, polysaccharides and proteoglycans

Question 6

What are the functions of the glycocalyx ?

Answer 6

1 Protection:
Cushions the plasma membrane
Protects it from chemical injury

2. Immunity to infection:
   Enables the immune system to recognize and selectively attack foreign organisms
3. Molecular signature:
   Different cell types present different combinations of glycoproteins and proteoglycan on their surface
4. Cell communication:
   Information in the carbohydrate layer aids in cell-cell recognition and communication

Question 7

What is the cell cortex ?

Answer 7

The cell cortex is a specialised layer of cytoplasmic proteins found just beneath the plasma membrane
Provides mechanical support and structural integrity
Meshwork for transmembrane proteins and actin + spectrum filaments

Question 8

Describe the functional outcomes of the cell cortex achieves:

Answer 8

Cytokinesis - cell cortex regulates replicating cells dividing

Cell polarity - epithelial cells maintain cellular polarity by use of tight junctions, which the cell cortex is majorly involved in maintaining

Cell migration - For cells to migrate they need differentiate what side of the cell is moving forward (leading front) and what side is detaching to allow the forward movement

Membrane trafficking (endocytosis and exocytosis) - cell cortex helps form vesicles needed for these processes