Exercise 1: Activity 3 stimulating osmotic pressure

What does water concentration depend on?

# of solute particles present if there is an increase in solute concentration then there will be a decrease in water concentration

water moves down the concentration gradient therefore towards the solution with the ______________ concentration of _____________________

1. highest 2. solutes

1 Which membrane did not allow Na+ Cl- to pass through?

20 MWCO

1 The conditions were 9 mM albumin in the left beaker and 10 mM glucose in the right beaker with the 200 MWCO membrane in place. Explain the results. How well did the results compare with your prediction?

Albumin is too big to move across the 200 MWCO membrane while glucose is able to move across and reach equilibrium. Since water is moving to the area with more concentrated solutes its moving to the left which increases the pressure.

1 Explain the effect that increasing the Na+ Cl- concentration had on osmotic pressure and why it has this effect. How well did the results compare with your prediction?

By increasing the concentration of sodium chloride from 5.0 mM to 10.0 mM it caused an increase in osmotic pressure. Since water moves toward the solution with the highest concentration of solutes it increases the osmotic pressure.

1 Describe one way in which osmosis is similar to simple diffusion and one way in which it is different.

Osmosis is similar to simple diffusion because it is moving from higher concentration to lower concentration. Osmosis is different than simple diffusion because it is talking about the movement of water across a semipermeable membrane rather than the movement of solutes.

1 If you double the concentration of a nondiffusible solute that is on one side of a membrane, the osmotic pressure will

double

1 When a solute is able to diffuse through a membrane

equilibrium is reached

hypotonic

if the concentration of impermeable solutes is lower outside then inside

isotonic

if the concentration of impermeable solutes is the same inside and outside of the cell

hypertonic

if there is a higher concentration of impermeable solutes outside of the cell then inside

What do you think will be the pressure result of the current experimental conditions?

pressure above the left beaker

1 Which of the following occurs when a hypertonic solution is added to cells?

the cell shrinks

1 The variable that affects osmotic pressure is

the concentration of nondiffusing solutes.

tonicity

the way a solution affects the volume of a cell 1. isotonic 2. hypertonic 3. hypotonic

When does osmosis occur?

when water concentration is different on the two sides of a membrane