Osmosis

Question 1

What is osmosis?

Answer 1

The passage of water from a region where it has a higher water potential to a region where it has a lower water potential through a selectively permeable membrane.

Question 2

What type of membranes are selectively permeable?

Answer 2

Cell-surface membranes and other plasma membranes around organelles.

Question 3

What is a solute?

Answer 3

Any substance that is dissolved in a solvent, for example, water.

Question 4

What is water potential represented by?

Answer 4

The Greek letter psi (Ψ).

Question 5

What is the water potential of pure water under standard conditions?

Answer 5

Zero.

Question 6

What effect does adding a solute to pure water have on its water potential?

Answer 6

It lowers the water potential.

Question 7

What is the water potential of a solution always?

Answer 7

Less than zero (a negative value).

Question 8

How does the concentration of solute affect water potential?

Answer 8

The more solute that is added, the lower (more negative) its water potential.

Question 9

In what direction does water move by osmosis?

Answer 9

From a region of higher (less negative) water potential to one of lower (more negative) water potential.

Question 10

How can the water potential of cells or tissues be determined?

Answer 10

By placing them in a series of solutions of different water potentials until there is no net gain or loss of water.

Question 11

What happens to animal cells when placed into pure water?

Answer 11

They may swell and potentially burst due to water influx.

Question 12

What happens to plant cells when placed into pure water?

Answer 12

They become turgid as water enters, but the cell wall prevents bursting.

Question 13

Fill in the blank: Osmosis is the movement of _______ molecules only.

Answer 13

water

Question 14

True or False: Osmosis involves the movement of both solute and water molecules.

Answer 14

False.

Question 15

What is the primary factor that drives osmosis?

Answer 15

The difference in water potential.

Question 16

What is the relationship between kinetic energy and molecular movement in osmosis?

Answer 16

Both solute and water molecules are in random motion due to their kinetic energy.

Question 17

What is the practical link mentioned for osmosis?

Answer 17

Production of a dilution series of a solute to produce a calibration curve for identifying the water potential of plant tissue.

Question 18

What type of membrane is described as selectively permeable?

Answer 18

Plasma membrane

The selectively permeable plasma membrane allows certain molecules to pass while restricting others.

Question 19

What molecules can cross the selectively permeable plasma membrane?

Answer 19

Water molecules

Solute molecules cannot pass through the selectively permeable plasma membrane.

Question 20

From which side do water molecules diffuse across the plasma membrane?

Answer 20

From the side with higher water potential

Water molecules move to the side with lower water potential.

Question 21

What is the term for the movement of water molecules from high to low water potential?

Answer 21

Diffusion

This movement occurs down a water potential gradient.

Question 22

What occurs when the water potentials on either side of the plasma membrane are equal?

Answer 22

Dynamic equilibrium is established

At this point, there is no net movement of water.

Question 23

Fill in the blank: Water molecules diffuse from the left-hand side, which has the higher water potential, to the right-hand side, which has the _______.

Answer 23

Lower water potential

Question 24

True or False: The plasma membrane allows both water and solute molecules to cross.

Answer 24

False

The plasma membrane only permits water molecules to cross.