Biological Membranes Flashcards
why do we need membranes?
to separate the inside from the outside of the cell
what is compartmentalisation?
the separation of different membrane bound organelles in a cell
why is compartmentalisation important?
it allows different organelles to maintain their own conditions needed for separate reactions
describe the structure of the plasma membrane
contains a phospholipid bilayer with hydrophobic and hydrophilic regions. Cholesterol in between phospholipids. Proteins embedded within membrane, intrinsic, and proteins (glycoproteins) sticking out, extrinsic. glycolipids sticking out too.
describe the fluid-mosaic model of the cell
fluid- phospholipids free to move due to cholesterol
mosaic- proteins all different sizes and positions.
what is the average thickness of the membrane?
7nm
what are intrinsic proteins?
proteins embedded within the membrane
how do intrinsic proteins stay in place in the membrane?
have amino acids with hydrophobic R groups on external surface which interact with the hydrophobic core of membrane, keeping in place
what are intrinsic proteins involved in?
transport across the membrane
what do channel proteins do?
provide a hydrophilic channel that allows PASSIVE movement of IONS and POLAR MOLECULES
what do carrier proteins do?
change shape to allow active transport of molecules into cell. act as pump.
describe how carrier proteins allow molecules and ions to move into the membrane against a concentration gradient
- the molecule binds to the receptor on the carrier protein outside the cell
- on inside, ATP binds to carrier proteins and is hydrolysed to form ADP and phosphate
- binding causes protein to change shape, so it able to open up
- molecule released inside cell
- phosphate molecule released from carrier protein and binds back to ADP to form ATP
- carrier protein returns to original shape
what are glycoproteins?
intrinsic proteins with carbohydrate chains attached
the actual protein not chain
role of glycoproteins?
- cell surface recognition
- cell surface antigenicity (such as the blood group antigens)
- act as receptors or binding sites
- help blood clotting
- immunological molecule
- cell adhesion
which part of membrane involved in cell signalling and describe
glycoproteins
- chemical binds to receptor (protein) and elicits a response from inside the cell
