3. movement in and out of cells

Question 1

describe the roles of water

Answer 1

1. digestion : for hydrolysis of food molecules
2. excretion : water is the solvent for removal and dilution of toxic substances
3. transportation : transport medium by being an
   essential constituent of blood plasma

Question 2

describe the term ‘diffusion’

Answer 2

the net movement of molecules and ions from a region of higher concentration to lower concentration down a concentration gradient

Question 3

list the factors affecting diffusion

Answer 3

1. surface area - the greater the surface area, the greater the rate of diffusion
2. temperature - the higher the temperature, the more energy the molecules have therefore greater speed to diffuse
3. concentration gradient - the steeper the concentration gradient, the greater the rate
4. distance - greater distance, lesser diffusion rate because molecules have to travel more

Question 4

describe the term ‘osmosis’

Answer 4

the net movement of water molecules from a region of higher concentration to lower concentration through a partially permeable membrane

Question 5

what happens to an animal cell if it is placed in a solution with lower water potential

Answer 5

the cell shrinks and loses its shape due to dehydration

Question 6

what happens to an animal cell if it placed in a solution with higher water potential

Answer 6

the cell increases in size until it bursts

Question 7

what happens to a plant cell if it is placed in a concentrated solution (low water potential)

Answer 7

water leaves the cell by osmosis and the cell decreases in size becoming plasmolyzed and flaccid

Question 8

what happens to a plant cell if it placed in a dilute solution (high water potential)

Answer 8

water enters cell by osmosis and enlarges becoming turgid

Question 9

describe the term ‘active transport’

Answer 9

the net movement of molecules or ions into or out of a cell through the cell membrane from a region of lower concentration to higher concentration

Question 10

what is the importance in root hair cells

Answer 10

Active transport in the root hairs of plants allows plants to absorb mineral ions, which are necessary for healthy growth, even though the concentration of minerals is usually lower in the soil than in the root hair.