Transport Across the Cell Membrane: Diffusion, Osmosis, and Active Transport 🌊

1. Diffusion 🌬️

Definition: Diffusion is the movement of particles from a region of higher concentration to a region of lower concentration, down their concentration gradient. 📉

Experiment to Demonstrate Diffusion 🔬

• Materials: 250 cm³ beaker, Long glass tube, Holed rubber stopper, Potassium permanganate or copper (II) sulfate crystal, Water. 🧪💧
• Method:
  • Insert one end of the glass tube halfway into the rubber stopper. 🧪
  • Place the stopper and tube at the bottom of the beaker. 📍
  • Introduce the colored crystal down the tube. 💎
  • Cover the open end of the tube with a finger and fill the beaker halfway with water. 🤚💧
  • Carefully lift the stopper and tube out without disturbing the crystal. 🚫💎
  • Observe what happens. 👀
• Observations: The color spreads through the water due to diffusion. 🌈
• Conclusion: Particles move from areas of higher concentration (the crystal) to lower concentration (the water). 🔄

Factors Affecting the Rate of Diffusion:

• Concentration Gradient: The larger the difference in concentration, the faster the diffusion. 📈
• Surface Area: A larger surface area speeds up diffusion. 🌐
• Thickness of the Membrane: Thinner membranes increase the diffusion rate. 🧬
• Temperature: Higher temperatures increase particle movement and speed up diffusion. 🌡️
• Particle Size: Smaller particles diffuse faster than larger ones. ⚖️

2. Osmosis 💧

Definition: Osmosis is the movement of water molecules from a region of higher water potential to a region of lower water potential through a selectively permeable membrane. 🚪

Experiment to Demonstrate Osmosis 🔍

• Materials: Three glass tubes, Selectively permeable membranes, Solutions of varying concentrations. 🧪💧
• Observations:
  • In Tube A (hypotonic solution): The liquid level drops as water moves out of the tube. 📉
  • In Tube B (isotonic solution): The liquid level remains the same. ⚖️
  • In Tube C (hypertonic solution): The liquid level rises as water enters the tube. 📈
• Conclusion: Water moves from areas of higher water potential to lower water potential. 🔄

3. Active Transport ⚡

Definition: Active transport is the movement of particles against their concentration gradient using energy from ATP. 🔋

Examples of Active Transport:

• Ion uptake by root hairs. 🌱
• Glucose absorption in the small intestine. 🍞