Structure of cell membrane Flashcards
(Specific structure of phospholipid bilayer)
What is the cell membrane bilayer made from
Phospholipids
How are the phospholipids in a bilayer placed
The hydrophilic phosphate head faces outwards and the hydrophobic tails face inwards
What is the function of the phospholipid bilayer
Forms a barrier to dissolved substances. The centre is hydrophobic so water soluble molecules cannot pass. However, only small, non-polar and lipid soluble molecules can diffuse through by simple diffusion. (CO2, O2 and Water)
What is the full cell membrane bilayer called
The fluid-mosaic model
Why is the cell membrane bilayer known as fluid and mosaic
Fluid - Because the phospholipids are constantly moving and sliding over eachother
Mosaic - Because the proteins scattered through the bilayer are like tiles in a mosaic
3 Functions of phospholipid bilayer (3 Marks)
*Allow lipid soluble substances to enter and leave the cell
*Prevent water soluble substances from entering and leaving the cell
*Make membrane flexible and self-sealiong
Where is cholesterol located in the phospholipid bilayer
Scattered in between the tails
Function and role of cholesterol
Reduces movement of phospholipids reducing the fluidity of the membrane and provides strength
They are also very hydrophobic so prevent the leakage of water and dissolved ions preventing permeability
Three types of proteins in the cell membrane
Extrinsic proteins, Intrinsic proteins and glycoproteins
The two types of intrinsic proteins
Protein channel and carrier protein
Protein channel
Contains water in the middle and allows water soluble molecules to pass through the cell membrane by dissolving them down the middle and letting them through by facciliated diffusion
Carrier protein
Performs facilitated diffusion to large or polar molecules that need to get through the cell membrane
Role of extrinsic proteins
These are proteins partially embedded in the cell membrane and they provide mechanical support and act as cell receptors for hormones
Glycolipids and glycoproteins
Lipids and extrinsic proteins with a carbohydrate group attached to them
Glycolipid role
Extends into tissue fluid outside of the cell
Acts as receptor sites
Maintain stability of membrane
Helps cell attach to eachother to form tissue
