Osmosis

Question 1

How does water move across the plasma membrane?

Answer 1

Through aquaporins when there is a driving force fo osmotic pressure

Question 2

What is osmotic pressure and the movement of water determined by?

Answer 2

The number of molecules (solutes) in the solution

Question 3

What is osmosis?

Answer 3

The free movement of water across a membrane in response to a solute concentration gradient

Question 4

The overall concentrations of the ECF and ICF are equal so why are they in chemical disequilibrium?

Answer 4

Some solutes may be more concentrated in one compartment than the other

Question 5

What is molarity?

Answer 5

The number of moles of dissolved solute in 1 litre of solution (mol/L)

Question 6

What is an osmole?

Answer 6

Unit of measurement that defines the number of moles of a solute that contribute to the osmotic pressure

Question 7

How are osmoles/L calculated?

Answer 7

Molarity X number of particles per molecule

Question 8

What does hypotonic mean?

Answer 8

A lower osmotic pressure

Less solute in the solution

Question 9

If a solution is hypotonic to the cell what will happen to the cell?

Answer 9

The cell will sweel and water will move down the osmotic gradient into the cell

Question 10

What does hypertonic mean?

Answer 10

A higher osmotic pressure

More solute in the solution

Question 11

If a solution is hypertonic to the cell what will happen to the cell?

Answer 11

The cell will shrink

Water will move out of the cell into the solution

Question 12

RBC’s put in a solution of glucose at the same concentrations - what will happen?

Answer 12

RBC’s have no glucose transporters so there will be no movement and they will stay in equilibrium - isotonic solutions

Question 13

RBC’s put in a solution fo urea at the same concentration - what will happen?

Answer 13

RBC’s have urea transporters so urea will diffuse into the cell and bring water with it and the cell will swell this is hypotonic effect in an isotonic solution

Question 14

Why can osmolarity alone not predict the tonicity?

Answer 14

Depends on if the molecule is permeable or impermeable

Question 15

How is an isotonic solution formed from permeable molecules?

Answer 15

The molecules can move across the membrane by diffusion so the cell and solution will eventually become isotonic

Question 16

How do cells and solution become isotonic with impermeable molecules?

Answer 16

The molecules cannot cross the membrane so water must move to accommodate this.
The cell and solution will eventually be isotonic but the cell/solution will by hypo/hyperosmotic

Question 17

Describe the oncotic pressure in the capillaries

Answer 17

At the arterial end hydrostatic pressure is higher than oncotic pressure so fluid is forced out = filtration
At the venous end hydrostatic pressure is lower than oncotic pressure so fluid is drawn in = absorption

Question 18

What happens when filtration and absorption int he capillaries are mismatched? (more filtration than absorption)

Answer 18

There is a net accumulation in the interstitial fluid.

The lymph system drains the extra fluid and returns it to the blood stream