CHAP 2 MOVEMENT OF SUBSTANCES

Question 1

Define OSMOSIS

Answer 1

Net movement of water molecules from a region of higher water potential to a region of lower water potential through a partially permeable membrane

Question 2

define DIFFUSION

Answer 2

net movement of particles from a region of higher concentration to a region of lower concentration down a concentration gradient

Question 3

Describe the role of diffusion in nutrient uptake & gaseous exchange in plants

Answer 3

Amoeba - diffusion is an important mode of nutrient uptake

Question 4

describe the role of diffusion in human gaseous exchange

Answer 4

• Body tissues are low in O2 as it is used up for cellular respiration
• RBC transport O2 to these body tissues during gaseous exchange
• O2 concentration in RBC is higher than O2 concentration in the body
• creates a concentration gradient
• causing oxygen to move out of the red blood cells & into the body cells

Vice Versa
- body tissues are high in CO2 as it is produced during cellular respiration
- CO2 concentration is higher in body cells than concentration in RBC
- creates a concentration gradient
-causing CO2 to move out of the body tissues & into the RBC to be transported away

Question 5

Describe the effects of OSMOSIS in PLANT CELLS
[ high surrounding WP ]

Answer 5

• Water potential in surrounding is higher than the water potential in the cell sap
• water moves into the cell by osmosis
• cell expands & becomes turgid due to presence of cellulose cell wall which prevents the cell from bursting

Question 6

Describe the effects of OSMOSIS in PLANT CELLS
[ lower surrounding WP ]

Answer 6

• water potential in surrounding is lower than the water potential in the cell sap
• water moves out of the cell by osmosis
• cells becomes flaccid
• cytoplasm shrinks away from the cell wall & becomes plasmolysed

Question 7

Describe the effects of OSMOSIS in ANIMAL CELLS
( higher surrounding potential )

Answer 7

• Water potential in surroundings is higher than the water potential in the cell
• water moves into the cell by osmosis
• the cell expands & burst due to absence of cell wall [ cytolysis ]

Question 8

describe the effects of OSMOSIS in ANIMAL CELLS
[ lower surrounding WP ]

Answer 8

• the water potential in surrounding is lower than the water potential in the cell
• water moves out of the cell by osmosis
• the cell shrinks & becomes dehydrated
• tiny spikes form on their cell surface membrane [ crenation ]