Movement of substances

Question 1

Compare and contrast between diffusion and osmosis [4]

Answer 1

Similarity:
Both involve net movement of molecules down concentration / water potential gradient
Slow and passive process / does not require additional energy input
Difference:
Osmosis is for water molecules only whereas diffusion is for any other molecules
Osmosis requires a partially permeable membrane, whereas for diffusion is with/without a partially permeable membrane.

Question 2

Compare between diffusion, osmosis and active transport and provide applications of each process in plants. [6]

Answer 2

diffusion and osmosis are passive processes that do not require additional energy whereas active transport require additional energy [1]
diffusion and osmosis are processes that result in net movement of molecules down conc / water potential gradient, whereas active transport is movement against the gradient [1]
diffusion and active transport are for all particles but osmosis is only for water molecules [1]
applications of diffusion in plants: mineral salts into leaf cells / gaseous exchange (O2 and CO2) via stomata, transpiration [1]
application of osmosis in plants: water into root hair cells / among neighbouring plant cells, turgidity of cells [1]
application of active transport in plants: mineral salts into root hair cells / translocation of sucrose and amino acids in phloem [1]

Question 3

Describe and explain how a typical plant cell will respond when soaked in distilled water. [5]

Answer 3

Higher water potential in distilled water compared to cell sap of plant cell[1]
Net movement of water molecules down the water potential gradient from distilled water
into plant cell[1]
Via osmosis[1]
The cell becomes turgid[1]
The cell wall can withstand the pressure to prevent cell bursting[1]

Question 4

Explain how a desert plant absorbs mineral salt and water into the roots. [6]

Answer 4

Mineral salt
Lower concentration of mineral salt in the soil than in the cell sap of the root hair cell. [1] Active transport of mineral salt against concentration gradient into the cell,[1] which require energy released from the oxidation of glucose in mitochondria during aerobic respiration. [1]
Water
Concentrated cell sap of root hair cell has lower water potential than the soil [1] due to concentrated mineral salt solution. Net movement of water molecules into the root hair cell [1] via osmosis across partially permeable cell membrane. [1]

Question 5

Explain how the use to poison to disrupt mitochondria function will have an impact on the mineral salt and water transport in the desert plant. [4]

Answer 5

Mineral salt
Lower concentration of mineral salt in the soil than in the cell sap of the root hair cell. Active transport of mineral salt is disrupted / blocked [1] due to no energy released from the oxidation of glucose in mitochondria during aerobic respiration. [1]
Water
Cell sap of root hair cell has higher water potential than the soil [1] due to lack of active transport of mineral salt from soil into root hair cell. Net movement of water molecules out of the root hair cell via osmosis [1] across partially permeable cell membrane. the plant losses water and dehydrates.