4.1.3.2 Osmosis

Question 1

Osmosis:

Answer 1

• The net movement of water molecules from a region of high water concentration to a region of low water concentration (down a concentration gradient) across a partially permeable membrane until equilibrium Is reached
• This is a passive process

Question 2

When is a solution dilute?

Answer 2

A solution is dilute when there is a high water concentration

Question 3

When is a solution concentrated?

Answer 3

A solutions is concentrated when there is a low water concentration

Question 4

A bag made from a Visking tubing (partially permeable membrane) is tied to a glass tube and filled with a strong sugar solution.
This bag is placed in a weak sugar solution.
What happens?

Answer 4

• Water molecules diffuse across the membrane from the weaker sugar solution (high water concentration) into the strong solution (low water concentration).
• This continues until the concentration is the same on both sides of the membrane.
• The volume of liquid in the semipermeable bag increases.
• The liquid rises up the glass tube and then stops.

Question 5

What does 0.0M sucrose mean?

Answer 5

0.0 M sucrose means there are 0.0 moles of sucrose - means no sugar

Question 6

What does the visking tube represent in the osmosis experiment?

Answer 6

The visking tube represents the cell membrane of a cell and it is partially permeable

Question 7

Hypotonic solution:

Answer 7

Outside the cell is less concentrated than inside the cell (more water outside - water moves into the cell)

Question 8

Isotonic solution:

Answer 8

Concentration is equal inside and outside the cell (no net movement of water molecules but some random movement)

Question 9

Hypertonic solution:

Answer 9

Outside the cell is more concentrated than inside the cell (less water outside - water moves out of the cell)

Question 10

How does lysis take place?

Answer 10

When the outside of the cell is more dilute (more water) than theinside (hypotonic), too much water mayenterand the cell willswell until it bursts

Question 11

How does crenation take place?

Answer 11

When the outside of the cell is more concentrated than the inside(hypertonic), too much water mayleaveand the cell will shrinkand shrivel

Question 12

Why won’t plant cells shrivel or burst from osmosis?

Answer 12

Plants cells have an inelastic (made of cellulose) cell wall, so won’t shrivel or burst

Question 13

How does a plant cell become turgid?

Answer 13

• When water enters the cell by osmosis it fills the vacuole
  Thispushes against the cell wall, making itturgid

Question 14

How does a plant cell becomes flaccid?

Answer 14

When water leaves a cell by osmosis, the vacuoleshrinksandthe cell becomesflaccid

Question 15

How does a plant cell becomes plasmolysed?

Answer 15

If too much water leavesthe cell, the cytoplasmmoves away from the cellwall and the cell becomesplasmolysed

Question 16

Diagram of an isotonic solution:

Answer 16

Question 17

Diagram of a hypertonic solution:

Answer 17

Question 18

Diagram of a hypotonic solution:

Answer 18

Question 19

Diagram of a turgid and flaccid plant cell:

Answer 19

Question 20

Diagram of a plasmolysed plant cell:

Answer 20

Question 21

Diagram of a red blood cell in an isotonic medium:

Answer 21

Question 22

Diagram of a red blood cel in a hypertonic medium:

Answer 22

Question 23

Diagram of a red blood cell in a hypotonic medium:

Answer 23

Question 24

What causes osmosis?

Answer 24

differences in the concentrations of the solutions inside and outside a cell cause the water to move into or out of the cell