Roles of membranes
- Created by: Jasmin
- Created on: 20-10-14 20:28
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- Roles
- Plasma membranes
- Partially permable -let some molecules in through but not others
- Controls which substances enter and leaves the cell
- They allow recognition by other cells (e.g. the cells of the immune system)
- Membranes within cells
- Membranes around organelles divides the cell into different compartments making the function more efficient.
- They can form vesicles to transport substances between different areas of the cell
- They control which substances ener and leave the organelle (e.g. RNA leaves the nucleus via the nuclear membrane)
- Phospholipids
- Forms a barrier to dissolved substance
- The head is hydrophillic -attracts water. The tail is hydrophobic -repels water
- The center of the bilayer is hydrophobic. So the membrane does not allow water soluble substances (like ions) through it
- Cholestrol
- Gives the membrane stability
- Cholestrol molecules fit beteen the phospholipids, causing them to pack more closely together. This makes the membrane less fluid and more rigid
- Proteins
- Channel proteins allow small and charged particles through
- Carrier proteins transport molecules and ions across the membrane by active transport and facilitated diffusion
- Proteins act as receptors for molecules (e.g hormones) inc ell signaling. When a molecule binds to the protein, a chemical reaction is triggered inside the cell
- Glucolipids and Glucoproteins
- Acts as receptors for messenger molecules
- Stabalises the membrane for forming hydrogen bonds with surrounding water molecules
- They are also sites where drugs hormones and antibodies bond
- They are also antigens -cell surface molecules involved in the immune response.
- Plasma membranes
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