Flashcards in Membranes Deck (25):
What does a ski-permeable membrane allow?
chemical gradients to be maintained across the membranes
What do organelle membranes do?
They separate differing regions of biochemistry, and allow for the specialist function of the various components of the endomembrane system.
What is the structure of cholesterol?
A hydrophilic head and a hydrophobic tail. (Four ring steroid structure and non-polar side chain).
What is the function of cholesterol?
Reduces membrane fluidity and prevents lipid crystallisation at low temperatures.
What properties do peripheral (or extrinsic) proteins have?
Easily removed from membranes in the laboratory using ionic washes.
What holds the peripheral proteins in place?
Charged or polar amino acid R groups, or by a small number of hydrophobic interactions
What properties do Integral (intrinsic) proteins have?
They cannot be washed away from the membrane.
What holds integral proteins in place?
The strong hydrophobic interactions with the lipid tails
What is the name given to a protein which spans the entire length of the membrane?
What is the name given to proteins and lipids which have carbohydrate chains added to them?
Glycoproteins or glycolipids
Where are the carbohydrate portion of glycolipids and glycoproteins found?
On the outside of the membrane
What are passive transport proteins?
Transmembrane proteins which transport molecules across a membrane down a concentration gradient.
What do channel proteins provide?
A pore that can facilitate or speed up diffusion
Give a detail of a channel protein
They are specific to one type of ion or molecule.
What do carrier proteins do?
They bind to a specific molecule to allow its passage
What does a gated transport protein infer?
The binding of one molecule is required for the passage of another.
What do active transport proteins do?
They pump ions and molecules against the concentration gradient
What does hydrolysis of ATP provide the energy for?
The phosphorylation and conformational change of the protein pumps.
What do membrane-bound enzymes allow?
The location of catalysis to be controlled within a cell
Which type of signalling molecules are unable to cross the hydrophobic region of the membrane.
Hydrophilic signalling molecules
What happens she transmembrane receptor proteins are signalled?
They stimulate a response within the cell such as phosphorylation of a key enzyme.
What do proteins provide in the membrane for structural support of the cell?
Cytoskeleton attachment points
What do other proteins attach to to keep the cell in place?
The extra-celular matrix
What do intercellular junctions do (formed by proteins)?
Provide anchorage to other cells and hold cells together in tissues.