Biological Membranes Flashcards
Main function of the cell membrane?
Protect the cells and its contents from surroundings and other cells.
How does the cell membrane provide cellular integrity?
A number of function and structures work together to allow the membrane to stand strong against extreme changes in environment (pH, temperature etc.)
What is the structure of the cell membrane composed of?
- Lipids & proteins (50/50)
- Phospholipid bilayer
What type of bonds hold together the structure of the membrane?
Non-covalent bonds
What type of proteins are attached and integrated within the membrane?
Structural proteins, transporters, sensors and receptors. These are known as membrane proteins.
What allows phospholipids to form a bilayer?
Phospholipids are amphiphilic, meaning they contain both hydrophobic/hydrophilic parts.
What is the chemical structure of a phospholipid?
What bond does it have?
Glycerol backbone and a phosphate. They are joined by an ester bond.
What group does cholesterol belong to?
Sterols
What is the function of cholesterol?
Provides rigidity to the membrane.
Which type of group does not contain any cholesterol in their cell membranes?
Bacteria. The cell wall provides rigidity cell wall in their case.
How are lipid bilayers formed?
- Hydrophilic lipid head exposed to water.
- Hydrophobic fatty acid tail group together
Is the lipid bilayer two-dimensional or three-dimensional?
Two-dimensional.
Which factors affect membrane fluidity?
- Lipid composition of membranes
- Temperature
- Cholesterol composition
How does an increase in unsaturated lipids affect fluidity?
Double bonds causes a ‘kink’ in the chain which allows less room for phospholipids to bunch together. This leads to a thinner membrane which is more flexible. Fluidity increases.
How does length of hydrocarbons affect the fluidity in membranes?
The shorter the hydrocarbons, less interaction so the membrane is thinner. Fluidity increases.
Lipid rafts contain…
higher levels of cholesterols and glycosylated sphingolipids.
Lipid rafts are involved in…
the organization of specific membrane proteins.
Primary function of lipid rafts.
Cellular signalling.
What is used as building block for membrane synthesis and as an energy source?
Lipids.
What is the role of phosphatidylserine?
It recognized by macrophages in apoptosis (programmed cell death).
Phosphatidylinositol is involved in…
cellular signalling.
Glycolipids are…
sugar-containing lipids.
Functions of glycolipids on the membrane…
- Cell recognition
- processes cell-cell adhesion
Extra reading…
Part IV Chapter 10 Membrane Structure.
What is the fluid mosaic model?
Fluid combination of phospholipids, cholesterol and proteins.
The two types of proteins associated within the membrane are called…
integral and peripheral.
Which compounds on the surface of the membrane allow proteins to be attached?
Covalent bound fatty acids, usually weak.
Which side is the asymmetry found on the membrane when it comes to membrane proteins?
Non-cytosolic side.
Majority of membrane proteins are modified with sugar through…
glycosylation.
Function of glycosylation?
Provide cell coat. (carbohydrate layer)
Protects against chemical and mechanical damage.
Prevents unwanted protein-protein interaction.
What type of molecules does the cell membrane allow through?
Hydrophobic molecules, H2O.
All charged polar molecules (except H2O) and ions are..
not able to pass through the cell membrane passively.
Which proteins allow passive transport?
Channels, transporters, electrochemical gradient.
Which proteins facilitate active transport?
Carrier proteins as it requires an energy input.
