Science (Key words and phrases)

Diffusion

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

Osmosis

The net movement of water molecules from a solution of higher water potential to a solution of lower water potential, through a partially permeable membrane

Active Transport

Substances move against the concentration gradient, in the presence of a partially permeable membrane

Osmosis (Animal cell - concentrated solution)

1. Cytoplasm has a higher water potential than the solution outside the cell

2. Water molecules leave the cell by osmosis through a partially permeable membrane

3. Cell shrinks in size (RBC crenates)

Osmosis (Animal cell - isotonic solution)

1. Cytoplasm has the same water potential as the solution outside the cell

2. No net movement of water molecules

3. Cell does not change in shape/size

Osmosis (Animal cell - diluted solution)

1. Cytoplasm has a lower water potential than the solution outside the cell

2. Water molecules enter the cell by osmosis through its partially permeable membrane

3. Cell expands in size and bursts/lyses

Osmosis (Plant cell - concentrated solution)

1. Cell sap has a higher water potential than the solution outside the cell

2. Water leaves the cell by osmosis through its partially permeable membrane \

3. Cytoplasm and cell membrane shrink away from the cell wall

4. Cell plasmolyses and becomes flaccid (soft)

Osmosis (Plant cell - isotonic solution)

1. Cell sap has the same water potential as the solution outside the cell

2. No net movement of water molecules

3. Cell remains the same size

Osmosis (Plant cell - diluted solution)

1. Cell sap has a lower water potential than the solution outside

2. Water molecules enter the cell by osmosis

3. Vacuole increases in size, causing the cell contents to be pushed against the cell wall

4. Cell enlarges and becomes turgid (firm)

*The cell wall prevents the cell from bursting

Answering questions about movement of substances

1. Difference in concentration/water potential

2. Identify the particles and state the direction in which the particles move

3. State the process involved diffusion, osmosis or active transport)

4. Result (cells → use the appropriate terms/key words)

Root hair cell adaptations

• long and narrow protrusion

• Increase surface area to volume ratio

• Increase the rate of absorption of water via osmosis

• And dissolved mineral salts form the soil via diffusion

Active transport

• Allows the root hair cell to continuously absorb water via osmosis

• Active transport requires energy released from cellular respiration

• Mitochondria in the RHC carry out respiration (glucose and oxygen needed)

  → Glucose is produced by the leaves during photosynthesis and oxygen enters the RHC any diffusion form the soil

• Active transport can occur and it causes the RHC to lower its water potential compared to that of the soil solution

• Water molecules continue to enter the RHC because the RHC’s water potential is always lower than that of the soil solution

Stem

• xylem and (water and dissolved mineral salts)

• Phloem (sucrose and amino acids)

Transmission of STI

Exchange of bodily fluids