Ch13: Diffusion and Osmosis

Question 1

Definition of selectively permeable membrane?

Answer 1

Allows some but not all molecules to pass through

Question 2

Name a thing* that is permeable in biological membranes and a thing* that is impermeable

Answer 2

Permeable: oxygen, carbon dioxide, water
Impermeable: Keratin

Question 3

Name 2 ways substances move in and out of cells

Answer 3

-Diffusion
-Active transport

Question 4

Definition of diffusion?

Answer 4

The spreading out of molecules from a region of high concentration to a region of low concentration

Question 5

Definition of active transport?

Answer 5

The movement of molecules from a less concentrated area to a more concentrated area, with the use of energy

Question 6

Name an example of diffusion:
1. in everyday life
2. in biology

Answer 6

1. Smell of perfume
2. CO2 and 02 diffusing in and out of body cells/leaves

Question 7

Definition of osmosis?

Answer 7

The movement of water molecules, across a semi-permeable membrane, from a region of high water concentration to a region of low water concentration

Question 8

Definition of solvent?

Answer 8

Liquid that dissolves other substances

Question 9

Definition of solute?

Answer 9

Substance that has been dissolved

Question 10

Definition of solution?

Answer 10

Mixture of a solute and a solvent

Question 11

Is osmosis a form of active transport or passive transport? What does this mean?

Answer 11

Passive transport
-means it does not require energy

Question 12

What happens when an animal cell is in a solution with the same concentration of solute as its cytoplasm?

What is this solution called?

Give examples of this

Answer 12

-Water will move in and out at the same rate, and the cell remains intact

-Isotonic medium

-Animals that live in the sea must have the same concentration
-In land animals, the kidneys ensure that the blood concentration is the same as the cell’s cytoplasm

Question 13

What happens when an animal cell is in a less concentrated (less solute) solution as its cytoplasm?

What is this solution called?

Give examples of this

Answer 13

-Water will move into the cell and may cause the cell to burst and die

-Hypotonic medium

-Amoeba

Question 14

What happens when an animal cell is in a more concentrated (more solute) solution as its cytoplasm?

What is this solution called?

Answer 14

-Water will move out of the cell causing it to shrivel and possibly die

-Hypertonic medium

Question 15

What is the optimum concentrated solution that an animal cell would like to be in?

Answer 15

Isotonic (equal concentration)

Question 16

Are cell walls permeable, impermeable or selectively permeable?

Answer 16

Fully permeable to water, gases and many solutes

Question 17

Definition of turgor pressure?

Answer 17

The outward pressure of the cytoplasm and vacuole against the cell wall of a plant

Question 18

Explain the cell wall in turgor pressure and its use

Answer 18

-The cell wall is rigid and prevents the cell from swelling

-Turgor pressure gives plant cells strength

Question 19

What happens when a plant cell is surrounded by a less concentrated (less solute) solution than its cytoplasm?

What is this solution called?

Give examples of this

Answer 19

Water moves into the cytoplasm and vacuole and gives the cell turgidity and strength

Hypotonic solution

This is how roots absorb water from soil

Question 20

What happens when a plant cell is surrounded by a more concentrated (more solute) solution?

What is this solution called?

Give examples of this

Answer 20

Water moves out of the cell and causes plasmolysis

Hypertonic solution

Lettuce leaves in salty dressing

Question 21

What is plasmolysis?

Answer 21

When the vacuole and cytoplasm shrivel due to the loss of water in a cell.

Causes the cell membrane to move away from the cell wall and the surrounding solution to fill the gap.

Causes the cell to lose turgor

Question 22

How are plant cells described in a:
1. Hypotonic solution
2. Isotonic solution
3. Hypertonic solution

Which is the optimum solution for a plant cell?

Answer 22

1. Turgid
2. Flaccid
3. Plasmolysed

Hypotonic solution is optimum

Question 23

What are the most common cause of food spoilage?

Answer 23

Bacteria and fungi

Question 24

How can osmosis be used during food preservation?

Answer 24

If food is placed in a salty or sugary solution, any bacteria or fungi present will lose water from their cells, shrivel and die

Question 25

Examples of osmosis in food preservation?

Answer 25

-Fish and meat soaked in a brine (salty solution) e.g. canned tuna

-Fruit is preserved in jams by using a high sugar concentration

Question 26

Describe an experiment used to test for osmosis

Answer 26

-2 visking tubing (1 with sucrose solution, one distilled water)
-Weigh both
-Let sit in beaker of distilled water for 15 mins
-Dry both tubes and weigh again
-Note change in weight and appearance