Transport across cell membranes (Chapter 4) BIOLOGY
Which components of the phospholipid bilayer are:
a) Hydrophobic
b) Hydrophilic
a) Fatty acid tails
b) Phosphate heads
Explain the arrangement of the phospholipid bilayer
The phospholipids form a bilayer. The hydrophobic fatty acid tails face inwards to avoid contact with water and the hydrophilic phosphate heads face outwards in order to attract water.
What molecules form the phospholipid bilayer?
Phospholipids, proteins, cholesterol, glycolipids, glycoproteins
Describe the structure and, as a result of these, the functions of proteins
- Some proteins occur in the surface of the bilayer-> they act either to give mechanical support to the membrane or, in conjunction with glycolipids, as cell receptors
- Other proteins completely span the bilayer. Some are protein channels and others are carrier proteins
What is a:
a) Carrier protein
b) Channel protein
a) Form water-filled tubes to allow water-soluble ions to diffuse across the membrane
b) Bind to ions/molecules, then change shape to move these across the membrane
What are the functions of proteins? Name 6
- Structural support
- Act as channel proteins
- Allow AT across the membrane
- Form cell-surface receptors for cell identification
- Help cells adhere together
- Act as receptors
Name 3 functions of cholesterol
- Make the membrane less fluid at high temperatures
- Prevent leakage of water and dissolved ions from the cell
- Reduce lateral movement of other molecules
Name 3 functions of the glycolipids
- Act as recognition sites
- Help maintain the stability of the membrane
- Help cells to attach to each other and so form tissues