4.1 Flashcards
How are the phospholipids arranged in the phospholipid bilayer? (3)
(1) 1 layer = hydrophilic heads = point INwards
(2) the other layer = hydrophilic heads = point OUTwards
(3) the hydrophobic tails = point to the centre of the membrane
What are the functions of the phospholipid bilayer? (3)
(1) allows lipid-soluble substances to enter & leave the cell
(2) prevent water-soluble substances to enter & leave the cell
(3) makes the membrane FLEXIBLE
What are the functions of a cell membrane? (3)
(1) forms a boundary between the cell’s cytoplasm & the environment
(2) allows different conditions to be established inside & outside the cell
(3) controls the movement of substances in & out of the cell
How are extrinsic proteins placed in the bilayer? (2)
What are the functions of extrinsic proteins? (2)
(1) they’re either on the surface of the bilayer…
(2) OR partly embedded in it
(3) It gives mechanical support
(4) in conjunction with glycolipids, they act as CELL RECEPTORS
How are intrinsic proteins placed in the bilayer? (1)
What are the functions of intrinsic proteins? (2)
(1) they completely span the bilayer from one side to another
(2) they act as CARRIERS to transport water-soluble molecules across the membrane
(3) they can be ENZYMES
What are the functions of proteins? (6)
(1) provides structural support
(2) allows the transport of water-soluble molecules
(3) allows the active transport of molecules
(4) form recognition sites
(5) help cells adhere together
(6) act as receptors
Why is the membrane described by the fluid-mosaic model? (2)
(1) because fluid = flexible
(2) because mosaic = there are PROTEINS of different sizes, shapes & patterns
Which 2 molecules in the membrane act as receptors? (2)
(1) glycoproteins
(2) glycolipids
What is the function of cholesterol in the membrane? (1)
(1) adds strength & rigidity to the membrane
