Biological Membranes Flashcards
(54 cards)
Name four components of the fluid mosaic Model of cell surface membrane
Fluid- phospholipids and proteins are free to move relative to each other - gives membrane flexibility
Mosaic- proteins are scattered and randomly arranged between the phospholipids
Intrinsic proteins- extended throughout the bilayer
Extrinsic proteins, partly embedded in bilayer they sit inside or outside the cell
Name all the parts of the plasma membrane
Glycolipid Glycoprotein Channel protein (intrinsic) Cholesterol Phospholipid bilayer Carrier protein (intrinsic) Phosphate head-hydrophilic Fatty acid tails-hydrophobic
What is the difference between a polar molecule and an ion
Ions have a full charge - molecules which have lost or gained electrons (Cl-)
Polar molecules- have an uneven distribution of charge across them (H20)
Describe the phospholipids the form the bilayer
Hydrophobic fatty acid tails pointing inwards and hydrophilic phosphate heads pointing outwards
What is the purpose of the hydrophobic region
To ensure that the fatty acids don’t come into contact with the water
And to separate aqueous regions from the inside and outside of the cell
What is the purpose of the phospholipid
To prevent legs molecules from leaving or entering the cell
Allows flexibility
What is cholesterol
A steroid molecule which fits within the bilayer between the fatty acid tails
What is the job of cholesterol
Increases the packing of the membrane and so reducing fluidity
Stabilises the membrane
What are the two main groups of proteins
Intrinsic proteins, eg channel proteins
Extrinsic proteins eg enzymes
Describe intrinsic proteins
embedded through both layers of the bilayer
Describe extrinsic proteins
Present on only one side of the bilayer
What is the job of channel proteins
To transport ions by facilitated diffusion, allow specific ions through, can be gated so can open and close in specific circumstances
What is the job of a carrier proteins
Only allow specific large molecules to pass through , when it binds it changes the shape and transfers the molecule to the other side of the membrane
( active transport of water soluble molecules and charged ions uses ATP)
What does gated mean and what does this apply to
Can open and close in specific circumstances
Channel proteins
What are:
A) glycoproteins
B) glycolipids
Glycoproteins are proteins with a carbohydrate chain attached
Glycolipids are lipids with carbohydrates attached
What are glycoproteins used in
Cell adhesion and receptors for cell signalling
What are glycolipids used for
Cell antigens used to recognise cells as self or non self
What is the role of the cell surface membrane:
- separates cell content from external environment
- cell signalling
- cell recognition
What are the jobs of membranes inside of cells
- compartmentalisation
- site of chemical reaction
- provides an attachment site for enzymes
- form vesicles for the transport of proteins
- attachment site for pigment
- membranes allow cellular compartment to have different conditions
What is cell signalling
The process that leads to communication and coordination between cells, so they can work together to trigger a response
What occurs during cell signalling
A receptor in the cells plasma membrane picks up signals
The signal will be in the form of a hormone or chemical mediators binding to the receptor
The binding to receptor brings about the appropriate response within the cell
Describe the structure and function of hormone receptors
protein and glycoproteins receptors found sticking out from target cells have a specific shape which is complimentary only to the shape of a specific hormone
The hormone binds to the receptor allowing the cell to respond appropriately
What is insulin
What’s it job
A blood based hormone
To lower blood glucose concentration levels
What happens when blood glucose levels gets too high
The pancreas secretes insulin which is carried in the blood
insulin binds to the insulin
receptor on liver or muscle cells which causes a chemical to be released which causes more glucose transport proteins to be inserted into the membrane increasing facilitated diffusion of glucose into cells
Also activated enzymes that convert glucose into glycogen for storage
