Diffusion and Osmosis

Question 1

What is a solute?

Answer 1

Dissolved substances in a solution (e.g. glucose, sucrose, ions [Na+, K+, Cl-]).

Question 2

What is a solvent?

Answer 2

A liquid that holds solutes (generally water).

Question 3

What is a solution?

Answer 3

A mixture formed when solute dissolved in a solvent.

Question 4

What is diffusion?

Answer 4

The movement of molecules from a high concentration to a low concentration. It continues until molecules are evenly distributed.

Question 5

What is facilitated diffusion?

Answer 5

The movement of large, water-soluble molecules or electrically charged molecules across the plasma membrane.

Question 6

What molecules does facilitated diffusion often move?

Answer 6

Amino acids & glucose in, manufactured proteins out.

Question 7

What is osmosis?

Answer 7

Osmosis is the diffusion of water across a selectively permeable membrane (plasma membrane).

Question 8

What does a selectively permeable allow to pass?

Answer 8

A selectively permeable membrane lets water pass through but not any solutes dissolved in the water.

Question 9

What is the effect of a semi-permeable membrane on a solution?

Answer 9

1. Solute added to one side of the beaker is too big to cross through pores in the membrane.
2. Solute distributes itself in 1/2 of the beaker. Water moves from an area of low solute concentration to high solute concentration.
3. Water on one side increases as the other decreases (moving down its concentration gradient).

Question 10

What is the effect of the concentration of a solution?

Answer 10

The concentration of the solute determines how much water moves across the membrane. The more concentrated a solution is, the more the solution will “pull” water towards it.

Question 11

What is osmolarity?

Answer 11

The “pull” on water created by solutes.

Question 12

What is osmolarity measured in?

Answer 12

Osmoles/L or mOsmoles/L

Question 13

What is the relationship between concentration and osmolarity?

Answer 13

A solution with a low concentration of solutes will have a low osmolarity value.
A more concentrated solution will have a high osmolarity value.

Question 14

What is the osmolarity of the intracellular fluid of a normal cell?

Answer 14

290mOsmol/L.

Question 15

What is an isotonic solution?

Answer 15

When a cell is placed in a solution that has the same osmolarity as the inside of the cell.

Question 16

What is a hypertonic solution?

Answer 16

When a cell is placed in a solution that has a higher osmolarity than inside the cell. As a result, the cell loses water and shrinks as water is diffusing out of the cell.

Question 17

What is a hypotonic solution?

Answer 17

When a cell is placed in a solution that has a lower osmolarity than inside the cell. As a result, the cell exerts a stronger pull on water, the cell takes in the water and then bursts.