the fluid mosaic model Flashcards
(45 cards)
What is the membrane structure composed of?
Lipids, proteins and carbohydrates
What type of lipid is the structure made of?
Phospholipids
What is a phospholipid?
A type of lipid (a glycerol molecule) with a phosphate group attached to it and two fatty acid tails
What is the fluid Mosaic model?
A form of the cell surface membrane, composed of two layers of fatty acids and phosphate groups assembled into opposing sheets
What do the phospholipid molecules form?
A flexible, thin, continuous double layer (bilayer)
Why is this arrangement fluid?
The phospholipids are constantly moving
What is the structure of the phospholipid molecule?
They have a hydrophilic head and a hydrophobic tail
What is the structure of the head of a phospholipid molecule?
The head contains a phosphate group and because its hydrophilic it attracts water and is polar
What is the structure of the tail of a phospholipid molecule? And what do the tails form?
The tail is made of two fatty acids and because its hydrophobic it will repel water and is non-polar. The tails form fatty acid chains
Which way do the hydrophilic heads face in the bilayer?
The hydrophilic heads face out towards the water on either side of the membrane
Which way do the hydrophobic tails face in the bilayer
The hydrophobic tales are on the inside making the centre of the bilayer hydrophobic
Why don’t membranes allow water soluble substances through it?
Because the centre of the bilayer is hydrophobic meaning that water-soluble substances like ions will be repelled
Why does the fluid music structure reference mosaics?
Because protein molecules are scattered through the bilayer like tiles in a mosaic
Are the proteins scattered throughout the bilayer stationary?
No, because phospholipid bilayer is fluid the proteins can move around within it. They can slide around the membrane very quickly and collide with each other, but can never flip from one side to the other
What are the 6 types of protein?
Integral proteins, peripheral proteins, transport proteins, receptor proteins, recognition proteins and structural proteins
What do integral/ channel proteins do?
What do they form?
They span from one side of the phospholipid bilayer to the other
They form protein tunnels that allow specific molecules to pass through the cell membrane, often acting as cell receptors
What do peripheral proteins do?
These sit on one of the surfaces and form a temporary bond with the cell membrane allowing them to detach and reattach at specific times with specific signals and
What do peripheral proteins allow the cell to do?
Coordinate and communicate using a network of proteins and reactions
What do integral proteins allow the cell to do?
Channelling and transporting molecules across the membrane
What are recognition proteins ?
Often glycoproteins embedded in the cell membrane which allow cells to communicate with others
What is an example of recognition protein?
The A and B antigens on red blood cell membrane
What do the transport proteins do?
Where does the transport take place?
Allow the transport of most small molecules across the membrane
It takes place through it integral proteins which provide hydrophilic channels for the passage of ions and polar molecules?
What examples of transport do transport protein allow?
Facilitated diffusion and active transport
What are receptor proteins?
Proteins that are on the outside surface of the cell membranes and have a specific binding site where hormones or other chemicals combined to form a hormone receptor complex
