Plasma membranes Flashcards
What is the model used to describe the plasma membrane as phospholipids that are free to move making them flexible and also because of the varying sizes of proteins in the layer?
Fluid Mosaic model
What are intrinsic/integral proteins ?
proteins embedded in both layers of the membrane.
What do channel proteins allow to happen?
The passive movement of polar molecules down a concentration gradient
How are channel proteins held in place ?
Interactions between the hydrophobic core of the membrane and the hydrophobic r-groups n the outside of the proteins
What do carrier proteins do ?
Play a role in passive transport but also active transport, often involving the shape of the protein changing.
How are glycoproteins involved in cell signalling?
They act as receptors for neurotransmitters and the binding of neurotransmitters at synapses then triggers or prevents an impulse in the next neuron.
Can also be receptors for peptide hormones.
What do glycolipids do ?
Called cell markers or antigens and are recognised by the immune system as self or non-self.
What are extrinsic/peripheral proteins ?
proteins present on one side of the bilayer that’s hydrophilliic r-groups interact with the polar heads of the phospholipids or intrinsic proteins. Some move between layers.
Why is cholesterol found in the plasma membrane ?
Positioned between the phospholipids they regulate fluidity of the membrane by preventing the phospholipids grouping too closely and crystallising.
What two factors affect membrane structure?
Temperature and solvents
What ways can temperature affect a membrane?
Temperature gives the phospholipids kinetic e energy to move around which makes the membrane more fluid and eventually lose the structure and the cell will break down completely as structure increases permeability and particles can cross it easier.
Membrane permeability is also affected when high temperatures cause carrier and channel proteins to denature.
Why do solvents break down membranes?
Membranes rely on the polar nature of water as it keeps the bilayer together as the tails of the phospholipids orientate away from it. Organic solvents are less polar than water so disrupt the membrane, making it more permeable.
