Movement Of Substances

Question 0

What is the criteria for diffusion to take place ?

Answer 0

Can only take place if there is a concentration gradient.

Question 1

Define ‘diffusion’.

Answer 1

Net random movement of molecules of a substances from a region of higher concentration to a region of lower concentration, down a concentration gradient.

Question 2

What is concentration gradient?

Answer 2

Difference in concentration of a substance between 2 regions.

Question 3

What is a partially/selectively permeable membrane?

Answer 3

Membrane which allows some substances to pass but not others.

Question 4

Define ‘Osmosis’.

Answer 4

Net movement of water molecules from region of higher concentration to region of lower concentration across a partially permeable membrane, down a concentration gradient.

Question 5

What is osmotic concentration?

Answer 5

Presence of solute in a cell that causes water to move into it.

Question 6

What is water potential?

Answer 6

Measure of free kinetic energy of water in a system, or tendency for water to leave a system.

Question 7

What are the factors affecting diffusion rate?

Answer 7

1. Thickness of membrane.
2. Concentration gradient.
3. Surface area.
4. Size of molecules and ions.
5. Nature of any structure across which diffusion occurs.

Question 8

What is a hypotonic solution?

Answer 8

Solution with a lower osmotic potential( or high water potential) than another solution.

Question 9

What is an isotonic solution?

Answer 9

Solutions of equal osmotic potential( or water potential).

Question 10

What is a hypertonic solution?

Answer 10

Solutions with higher osmotic concentration( or lower water potential) than another solution.

Question 11

What is endosmosis?

Answer 11

Water enters cell by osmosis.

Question 12

What happens to a plant cell that is placed into a hypotonic solution?

Answer 12

1. Water enters cell into vacuole.
2. Presence of cell wall(strong and elastic), it prevents over expansion of cell by exerting opposing pressure preventing further entry of water.
3. Cell become turgid.

Question 13

What is turgor pressure?

Answer 13

Pressure exerted outwards by water on cell wall.

Question 14

What happens to an animal cell placed in a hypotonic solution?

Answer 14

Cells will swell and may actually burst.

Question 15

What happens to cells placed in an isotonic solution?

Answer 15

1. Exosmosis and endosmosis skes place at equal rates.
2. Rate of water equals rate of water gain.
3. Thus cells remain in same shape.

Question 16

What is exosmosis?

Answer 16

Water leaves cell through osmosis.

Question 17

What happens to animal cells placed in hypertonic solution?

Answer 17

Cells shrink in size(become dehydrated)- crenated cells.

Question 18

What happens to a plant cell placed in a hypertonic solution?

Answer 18

1. Vacuole decreases in size, cytoplasm shrinks away from cell.
2. Cell decreases in size and becomes flaccid.

Question 19

What is plasmolysis?

Answer 19

Shrinkage of cell cytoplasm away from cell wall when cell is immersed in hypertonic solution.

Question 20

What is incipient plasmolysis?

Answer 20

Stage where protoplasm is just beginning to pull away from cell wall.

Question 21

How can plasmolysed cells be restored to their original shape?

Answer 21

By placing them into hypotonic solution, cells will be killed if they remain plasmolysed for too long.

Question 22

What is the importance of turgor in plants?

Answer 22

1. Maintains shape of soft tissues in plants.

2. Movement of certain plant parts.

Question 23

Define ‘Active transport’.

Answer 23

Movement of substances from region of lower concentration to region of higher concentration, against concentration gradient.

Question 24

Why is energy needed in active transport?

Answer 24

This process works against a concentration gradient.

Question 25

Where is the energy obtained from for active transport?

Answer 25

Cellular respiration.

Question 26

How is the movement like in active transport compared to diffusion?

Answer 26

Movement in AT us unilateral, unlike diffusion which is reversible.

Question 27

Name examples in which active transport is used.

Answer 27

1. Plant roots obtain mineral ions through root hairs.

2. Cells in villi of small intestine absorb soluble products.