Cell Membrane Flashcards
What is the cell membrane made out of?
It is composed of a bilayer of phospholipids which has proteins scattered throughout for different functions as well as cholesterol.
What are the common features of cell membranes?
- non-covalent assemblies
- asymetric
- specific proteins that carry out distinctive function
- fluid
- electrically polarised
- two molecules thick
How are the phospholipids arranged as?
- hydrophilic head which faces on the outside
- hydrophobic tail which faces on the inside
- due their interactions with water it creates a bilayer
What are the features of phospholipids?
Phospholipids (along with glycolipids) are amphipathic which means that they contain both contain hydrophobic and hydrophilic parts.
This means that its can form biomolecular sheets in aqueous media.
It can form a lipid bilayer/micelles which can be used to deliver drugs.
How does temperature affect the fluidity of the membrane?
In low temperatures, the membrane is packed tightly and the cholesterol makes the membrane even more rigid, making the permeability of the membrane decrease. In higher temperatures, the membrane will loosen but due the cholesterol it is still able to maintain the membrane shape- this means that the permeability has increased.
How does chain length affect the fluidity of the cell membrane?
Increasing the length of the chain will result in the rigidity of the cell membrane to increase as there will be an increase in the amount of interactions between the chians which ultimatley means that the cell membrane becomes less fluid.
How doe the extent of saturaiton affect the fluidity of the cell membrane?
If the lipid is more saturated, it means that the cell membrane will be more rigid and increasing the amount of straight chains present will result in an increase in the interactions, thus making the membrane less fluid.
How does having more cholesterol within the cell membrane affect the fluidty?
Within cholesterol there is a OH group which forms hydrogen bonds with the phospholipids fatty acid tail and this then distrupts the regular interaction between the fatty acid chains.
Where are phospholipids synthesised?
New phospholipids are synthesised on the cytosolic side and then transported by the flippase enzyme to the extracellular side.
What is apotosis?
It is the programmed death of a cell.
What are the steps involved in apotosis?
First the cell shrinks and form bubbles on the cell surface. The cell contents inside get chopped up and made into small chuncks that develops their own membrane. Within the cell mebranes, phosphatidylserine is prsent and acts as the ‘eat me signal’, a signal which attracts phagocytes to remove the cell fragments.
What are the different proteins types that can be found within the membrane?
- integral
- peripheral
- lipid anchored
- carbohydrates (glyolipids/glycoproteins)
What is a integral protein?
The a re proteins that are integrated into the membrane.
They have at least one hydrophobic region that anchors them to the hydrophobic core of the phospholipid bilayer. They also have a hydrophobic side chain.
Some stick only partway into the membrane, while others stretch from one side of the membrane to the other and are exposed on either side.
They are found in the transmembrane reigon and is alpha helix.
Have strong-non covalent bonds
Can pass through the membrane once or multiple times.
Since it is intelinked within the membrane it is very hard to extract.
What is a pheriperal protein?
They are proteins found on the outside and inside surfaces of membranes, attached either to integral proteins or to phospholipids. Unlike integral membrane proteins, peripheral membrane proteins do not stick into the hydrophobic core of the membrane, and they tend to be more loosely attached.
They are only associated by non-covalent bonds
Since they are loosely associated with the membrane, it makes it easier to extract.
What are lipid anchored proteins?
They are proteins that are covalently linked to a lipid molecule.(Lipoproteins)
