Module 11 Terms - Water Movement: Osmosis, Tonicity, and Osmoregulation

Question 1

Solutes

Answer 1

Dissolved substances

Question 2

Molarity

Answer 2

The concentration of a solute in a solution

Question 3

Osmosis

Answer 3

The movement of water across a selectively permeable membrane in response to a difference in solute concentration

Question 4

Water potential

Answer 4

All of the chemical and physical forces that affect the movement of water, such as osmosis, pressure, and gravity

Question 5

Osmotic pressure

Answer 5

The tendency of water to move from one solution into another by osmosis (higher solute concentration = higher osmotic pressure)

Question 6

Tonicity

Answer 6

A term used to describe osmotic pressure and the direction of water movement; describes how strongly water is pulled into one solution compared to another. A relative term used for comparisons

Question 7

Hypertonic

Answer 7

A solution with a higher solute concentration than another solution

Question 8

Hypotonic

Answer 8

A solution with a lower concentration than another solution

Question 9

Isotonic

Answer 9

A solution with the same concentration as another solution

Question 10

Contractile vacuoles

Answer 10

Organelles that take up excess water from inside the cell and then, by contraction, expel it into the external environment

Question 11

Pressure potential

Answer 11

The effect of pressure on the movement of water

Question 12

Solute potential

Answer 12

The effect of solutes on the movement of water

Question 13

Osmoregulation

Answer 13

The regulation of osmotic pressure inside cells and organisms

Question 14

What is high and low water potential and what does it mean?

Answer 14

If a solution has high water potential, it has a high concentration of free water molecules; conversely, if the solution has low water potential, it has a low concentration of free water molecules and tends not to move to other places.

Water has a tendency to move from areas of high water potential to low water potential.

Question 15

What is the water potential equation?

Answer 15

Ψ = Ψs + Ψp

Ψ is water potential
Ψs is solute potential
Ψp is water potential

Question 16

What are bars in terms of water potential?

Answer 16

Bars are basically just the quantified water potential, with the highest being 0 (pure water) and anything more negative than that having lower water potential.

Thus, if area 1 has a water potential of -40 bars and area 2 has a water potential of -5 bars, the water will flow from area 2 to area 1, because water moves from areas of high water potential (more positive in terms of bars) to areas of lower water potential (more negative in terms of bars).

Question 17

How does solute potential (Ψs) work?

Answer 17

If more solutes are added to a solution, the solute potential drops—in other words, it becomes more negative

Thus, if you added salt to pure water with a solute potential of 0, the solute potential would become more negative, say, -5 bars

Question 18

How does pressure potential (Ψp) work?

Answer 18

Pressure potential is basically the amount the solution is being pushed out of an area.

For example, if there is a lot of water in a plant cell, its cell walls will push against the water, making it want to go out of the cell. A positive pressure potential means there is a force acting on the water that motivates the water to exit an area

Make sure to remember that on problems where there is an open beaker or no other forces acting on the solution, Ψp is 0!

Question 19

What is the solute potential equation?

Answer 19

Ψs = -iCRT

i = ionization constant (anywhere from 1-2), depending if the solute will split into two molecules or not in solution
C = concentration (molarity)
R = pressure constant (ALWAYS 0.0831 liter bars/mole K)
T = temperature (273 + °C)