forces across membranes 1

Question 1

what can move freely between the ISF,ICF and plasma and what cannot?

Answer 1

gases move freely
nutrients and waste products move freely through carrier proteins.
ions do not move freely.

Question 2

8 features of membranes

Answer 2

1- selective barrier
2-flexible: due to presence of fatty acids which allow cells to shrink and swell
3: act as recognition site for molecules: receptors on surface bond to specific molecules due to complementary shape. this triggers a chemical reaction within the cell
4-act as a very good insulator: phospholipid bilayer allows electrical charge to be maintained within the cell
5- made up of a thin, bilayer of phospholipids
6- proteins embedded in structure
7-constantly being metabolised and adjusted according to the needs of the cell.
8-permeability may vary.

Question 3

different functions of proteins within the cell?

Answer 3

INTEGRAL PROTEINS: span the whole cell membrane. Same rotation as phospholipids. Amphipathic. If they are removed they alter the function of the membrane.
1- enzymes: catalyse reactions of cell-surface membranes.
2- receptor
3-transporter: channel and carrier
PERIPHERAL PROTEINS: Do not span the whole membrane. Are not amphipathic. If removed will not alter the function of the membrane

Question 4

how do the receptor proteins work?

Answer 4

they have a shape complementary to certain molecules.
if these molecules bind they lead to a chemical change within the cell.
the molecules they bind to are known as ligands ( neurotransmitters or hormones)
antagonists are molecules which have the same shape as ligands and can block the receptor site

Question 5

different type of protein transporters?

Answer 5

channel: form a continuous pore between the ECF and the ICF. water can always flow between them.
carrier: opens to ICF first and then ECF.

Question 6

function of peripheral-membrane proteins?

Answer 6

1-attach cell to extracellular matrix
2-bind cell to intracellular cytoskeleton
3-control cell interaction with other cells.

Question 7

different composition of cell- membranes

Answer 7

myelin: good insulator-has low protein content and high lipid content
plasma membranes; 50/50
energy transduction proteins: 75% protein due to many mitochondria

Question 8

different composition of lipid bilayer

Answer 8

may have lipids(glycolipids) or proteins(glycoproteins) attached to them EXTRACELLULARLY.
important in self-cell recognition.