Forces Acting Across Membranes

Question 1

4 main functions of membrane proteins

Answer 1

1. receptors
2. transporters
3. enzymes
4. maintenance of cell structure

Question 2

protein content of different membranes

Answer 2

myelin - 18% proteins
plasma membrane - 50%
inner mitochondrial membrane - 75%

Question 3

receptors

Answer 3

• integral membrane protein

- extracellular signal –> intracellular response

Question 4

transporters

Answer 4

1. channel proteins

2. carrier proteins (horseshoe shaped - larger molecules)

Question 5

porin

Answer 5

protein channel that is always open and filled with water so that small water soluble molecules can pass through.

Question 6

dystrophin protein

Answer 6

anchors cell membrane to intracellular cytoskeleton, is located on the inside of the cell membrane
- loss of these lead to DMD

Question 7

5 mechs of movement btw compartments

Answer 7

1. endo/exocytosis
2. diffusion
3. mediated transport
4. osmosis
5. filtration (not really related)

Question 8

why don’t give patient water through IV?

Answer 8

once it has entered circulation, water will move into nearby tissue to regain equal concentration inside and out of vessel wall and cause the tissue to rupture.
It would be good if solutes can move out of the cell into the blood, but membrane is not permeable to those, and water moved in from the plasma to the cells instead.

Question 9

normal plasma osmolarity and tonicity

Answer 9

285 milliosmoles/L

- since most of these are non penetrating, osmolarity and tonicity in the ECF is the same

Question 10

molarity vs osmolarity vs tonicity

Answer 10

molarity: molecules/L
osmolarity: particles/L
tonicity: like osmolarity, but only non penetration particles

tonicity is the most important because it can actually determine the cell volume

Question 11

an example of an isotonic solution commonly used

Answer 11

0.1% saline (150 mM)

will differentiate into 300 mM