2.1.5 Biological Membranes – Fluid Mosaic Model Flashcards
(15 cards)
What are the 5 components of the plasma membrane?
Phospholipids
Proteins
Cholesterol
Glycolipids
Glycoproteins
Why is the plasma membrane described as a fluid mosaic model?
The phospholipids are constantly moving and the proteins are scattered and randomly arranged between the phospholipids.
Why is the plasma membrane described as a bilayer?
The phospholipids line up in two layers with their hydrophobic tails pointing inwards and their hydrophilic heads pointing outwards and meeting the surrounding environment.
What is the structure of a phospholipid?
A hydrophilic head (made of a phosphate group and glycerol) and a hydrophobic tail (made of two fatty acid chains).
What is the function of the phospholipids in a plasma membrane?
- Allow lipid-soluble substances to enter and leave the cell.
- Prevent water-soluble substances from entering and leaving the cell.
- Give the membrane fluidity.
What is an extrinsic protein?
A protein that is located only on one side of the plasma membrane.
What is an intrinsic/integral protein?
A protein that spans from one side of the plasma membrane to the other.
What are the functions of extrinsic proteins?
Give mechanical support
Are enzymes
Act as receptors
What are the functions of intrinsic proteins?
Act as carriers to transport water soluble material across the bilayer
Form ion channels
Act as enzymes
What is the function of cholesterol?
It regulates the fluidity of membranes.
How does cholesterol regulate the fluidity of the plasma membrane?
Cholesterol binds to phospholipid fatty-acid tails, increasing the packing of the membrane, therefore reducing the fluidity of the membrane. More cholesterol in a membrane, means less fluidity of the membrane.
What is a glycolipid?
A molecule made up of phospholipid with a carbohydrate chain attached.
List two functions of glycolipids.
- Act as antigens
- Help cells join to other cells to form tissues
What is a glycoprotein?
A molecule made up of a protein with a carbohydrate chain attached.
List three functions of glycoproteins.
- Act as antigens in the immune system
- As receptor for hormones and neurotransmitters
- Help cells join to other cells to form tissues
