Osmosis

Question 1

describe chemical potential of water in relation to the amount of solute dissolved in it

Answer 1

chemical potential of water is proportionately reduced by the amount of solute dissolved in it

Question 2

what membrane protein allows passage of water via membranes?

Answer 2

Aquaporins

Question 3

What things in body have an abundance of aquaporins?

Answer 3

kidney, RBCs, brain, lung, salivary and lacrymal glands

Question 4

Which aquaporin mediates water movement in salivary glands?

Answer 4

Aquaporin-5

Question 5

Difference between osmolality and osmolarity?

Answer 5

Practically the same thing but osmolality is not affected by temperature while osmolarity is

Question 6

describe what the reflection coefficient (sigma) is?

Answer 6

it is introduced into the van’t hoff equation to reflect membrane permeability of a solute.

so sigma = 1 (impermeable solute)

sigma =0 (HIGHLY permeable solute)

Question 7

What maintains osmotic stability of living cells?

Answer 7

External Na+ (acts as an impremeable solute)

Question 8

Is sodium actually impremeable to a cell?

Answer 8

No… theres just a very active Na,K pump that extrudes Na as rapidly as it leaks into the cell

Question 9

Do living cells exist in donan equilibrium? If not, what state do they exist in?

Answer 9

NO. They exist in a steady state, where ions leak and are balanced by energy requiring pumps to maintain constant conditions