Biology Chapter: Diffusion and Osmosis

Gaining Water and Nutrients

• Objectives: define diffusion and osmosis, describe diffusion, explain osmosis with plant cell examples, differentiate between diffusion and osmosis, revise plant and animal cell differences, explain solution concentrations, explain osmosis with examples of plant and animal cells (like red blood cells), elaborate osmosis with experiments, and give a brief idea of stomata, transpiration, and active transport.

Diffusion

• Movement of particles from an area of higher concentration to an area of lower concentration.
• A passive process.
• In a cell, water always moves to reach equal concentration on both sides of the membrane.

Factors Affecting Diffusion Rate

• Concentration: Higher concentration = faster rate.
• Temperature: Higher temperature = faster rate.
• Size of molecules: Smaller size = faster rate.

Osmosis

• Movement of water molecules from higher concentration to lower concentration in the presence of a partially permeable membrane (e.g., cell membrane).
• Two conditions for osmosis to occur:
  • A semi-permeable membrane.
  • A difference in concentration.

Osmosis in Plant Cells

• Isotonic solution: Plant cell has normal shape and pressure.
• Hypotonic solution: Plant cells swell beyond normal size and pressure increases (making leaves firm).
• Hypertonic solution: Plant cell loses pressure, plasma membrane shrinks away from the cell wall (plasmolysis).

Osmosis in Animal Cells

• Isotonic solution: Water moves in and out at the same rate, cells retain normal shape.
• Hypotonic solution: Water enters the cell causing it to swell and potentially burst.
• Hypertonic solution: Water leaves the cell, causing it to shrink.

Active Transport

• Movement of materials through low concentration to high concentration against the concentration gradient.
• Requires energy from the cell.
• Minerals (nitrates, phosphates, potassium, and magnesium) are absorbed into root hair cells using active transport.

What do you expect to happen?

• If a bag with a strong sucrose solution is placed in distilled water, water will enter the bag through osmosis.

Experiment results

• If you place a potato slice in distilled water, the potato slice will swell.
• If you place a potato slice in salty water, the potato slice will shrink.

Transpiration

• Water evaporates from leaves through stomata.
• Responsible for water loss and movement throughout the plant.
• Helps in cooling the plant and distributing water to the top of tall trees.
• Rate depends on temperature, humidity, surface area, and sunlight intensity.

Stomata

• Stomata are pores in plant leaves.
• Open when guard cells are turgid.
• Closed when guard cells are flaccid.

Plant Cell Structures

• Chloroplasts
• Cell wall
• Golgi vesicles
• Golgi apparatus
• Membrane
• Peroxisome
• Amyloplast
• Vacuole
• Cytoplasm
• Ribosomes

Animal Cell Structures

• Lysosome
• Nucleus
• Nucleolus
• Rough ER
• Smooth ER
• Mitochondrion
• Cytoskeleton

Uses of Water in Plants

• Structural support
• Photosynthesis
• Body temperature regulation
• Solvent (dissolving substances within the plant body)

Test your understanding of diffusion and osmosis with this quiz. Explore core concepts such as the movement of water and nutrient particles across cell membranes, the differences between plant and animal cells, and the factors impacting these processes. Dive into real-life examples and experiments that illustrate these essential biological principles.