Describe the fluid-mosaic model of a plasma membrane. Discuss the role of the membrane in the movement of materials through it by each of the following processes:
Describe the fluid-mosaic model of a plasma membrane. Discuss the role of the membrane in the movement of materials through it by each of the following processes:
- Active transport
- Passive transport
The plasma membrane is composed of a phospholipid bilayer. That is, you have two phospholipids, which look like...jellyfish, as in they have a head and tails, these tails are hydrophobic, they don't like water, so they join together on the inside of the by layer, the heads are hydrophilic, so are on the outside, facing the liquid of the cell. So in the end it looks a bit like a zip, with tails in the middle, and heads on the outside. The individual lipids are not joined to each other, to things can "float" about in the layer, mainly proteins used for active transport .
Active transport, is going against the concentration gradient, sorta the opposite of diffusion. This uses the intrinsic proteins (the proteins that go all the way through the membrane) This works like a very selective gate, if a molecule lands on it, and it wants it in/out the cell, the protein will open at the end with the molecule, so the molecule enters the protein, the protein closes and opens the other side, letting the molecule out.
Passive transport is along the concentration gradient, so any molecules that have a lower concentration on one side of the membrane can easily pass through without the use of proteins. This is things such as diffusion.
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