Cell Membranes Flashcards
(12 cards)
What is the function of a cell membrane?
Control what molecules enter and exit the cell.
What is the molecule plasma membranes are made up of?
Phospholipids.
What is the structure of a phospholipid?
A glycerol attached with ester bonds to two fatty acids and a phosphate group.
The glycerol and phosphate group make up the hydrophilic head.
The 2 fatty acid chains make up the hydrophobic tail.
Why is the head hydrophilic?
The phosphate has to O- therefore is charged.
Can you describe the structure of a phospholipid bilayer?
Two chains of phospholipids running antiparallel to one another with their fatty acid tails pointing towards the opposite chain.
How does a micelle form?
The heads of the phospholipids are attracted to the water molecules as they are charged (hydrophilic).
The tails of the phospholipids don’t interact with the water as they have no charge (hydrophobic).
This results in all the fatty acids pointing to one another with a circle of heads surrounding them. There is no water in the micelle.
What can pass across the phospholipid bilayer?
Small, non charged, lipid soluble molecules.
What can not pass across the phospholipid bilayer?
A large molecule.
A water soluble molecule.
A charged/ polar molecule.
Why can’t large, polar, or water soluble molecules pass across the phospholipid bilayer?
The phospholipids form a hydrophobic barrier around the cell.
Can you give two properties of membranes?
Flexible and self healing.
Can you name some molecules that can pass across the phospholipid bilayer?
Ethanol
Oxygen
Carbon dioxide
Cholesterol
Oestrogen
(Water)
Can you name some molecules that can NOT pass across the phospholipid bilayer?
Salt- water soluble and becomes charged when dissolved.
Sugar- water soluble and too big.
Ions- charged.
Insulin- too big.
Amino acids- water soluble.
