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What is a cell membrane made of? And what on this earth is a phosolipid?

Hey Ive currently started my OCR AS Biology lessons cell membranes have REALLY confused me- what are they made of? Is it just phospholipids and please in the simplest terms possible what is a phospholipid?

Tanx guys!

Reply 1

maxwynne

I answered this in another thread but I'll do it again :smile:

The phospholipid bilayer is the membrane which controls which substances leave and enter the cellIt's called the fluid mosaic as the phospholipids are constantly moving. It is a bilayer as you can see there is two layers of phospholipids. The tails face each other as they are hydrophobic, and the heads face outwards as they are hydrophillic.

Reply 2

Tj789

Original post by maxwynne

I answered this in another thread but I'll do it again :smile:

Tanx for repeating - I know it could have been annoying!

Ok I think I get it just one thing, so when people says "the cell membrane controls what goes in and out of a cell" what they actually mean its the phospholipids that do that?

Reply 3

maxwynne

Well there are proteins in the phospholipid bilayer such as the carrier and channel proteins.
This is what I wrote in another thread, this might explain it

The proteins are in the bilayer and form channels .Channel proteins form pores for small ions and polar molecules to move through. As it is through a protein, the movement is called facilitated diffusion, and the molecules move down their concentration gradient.

Carrier proteins are slightly different, but are also in the phospholipid bilayer. They can transport large, polar molecules and ions in or out of cells. They can do this by facilitated diffusion - if the molecule is moving down the concentration gradient. Or it can do it by active transport if it is transporting the molecule against its concentration gradient. It works when a molecule attaches to a carrier protein in the membrane. The carrier protein changes shape, which then allows the molecule to be released on the opposite side of the membrane. When the carrier protein works by active transport, it uses ATP.