BIOLOGY KSSM FORM 4 CHAPTER 3 (3.2 & 3.3) Differences between PASSIVE & ACTIVE TRANSPORT. Examples

Key Concepts

• Passive Transport: Movement of substances across a membrane down the concentration gradient (high to low) without energy expenditure.
• Active Transport: Movement of substances across a membrane against the concentration gradient (low to high) requiring energy (ATP).
• Simple Diffusion: Movement of molecules directly through the phospholipid bilayer.
• Osmosis: Diffusion of water molecules across a semi-permeable membrane.
• Facilitated Diffusion: Movement of molecules across a membrane with the help of channel or carrier proteins.
• Concentration Gradient: The difference in concentration of a substance between two areas.
• Dynamic Equilibrium: A state where the concentration of a substance is equal across a membrane, resulting in no net movement.
• Carrier Proteins: Proteins that bind to specific molecules and transport them across the cell membrane by changing shape.
• Channel Proteins: Proteins that form a pore or channel in the cell membrane through which specific molecules or ions can pass.
• ATP (Adenosine Triphosphate): The primary energy currency of the cell.
• Sodium-Potassium Pump: An active transport mechanism that moves sodium ions out of the cell and potassium ions into the cell.
• Alveolus: Tiny air sacs in the lungs where gas exchange occurs.
• Root Hair Cell: Specialized epidermal cells of plant roots that absorb water and nutrients from the soil.
• Villus: Finger-like projections in the small intestine that increase the surface area for absorption.
• Epithelial Cells: Cells that line the surfaces of the body, including the villi of the small intestine.
• Cell Sap: The fluid inside the vacuole of a plant cell.
• Soil Solution: The water in the soil that contains dissolved minerals and nutrients.
• Water Potential: A measure of the relative tendency of water to move from one area to another.
• Turgor Pressure: The pressure exerted by the cell contents against the cell wall in plant cells.
• Plasmolysis: The contraction of the protoplast of a plant cell as a result of loss of water from the cell.
• Hypotonic: Having a lower solute concentration than another solution.
• Hypertonic: Having a higher solute concentration than another solution.

Passive Transport vs. Active Transport

Analogy and Basic Differences

• Passive transport is analogous to a person cycling downhill, requiring no energy. Substances move from an area of higher concentration to an area of lower concentration.
• Active transport is analogous to a person cycling uphill, requiring energy. Substances move from an area of lower concentration to an area of higher concentration.

Learning Standards

• Compare and contrast passive transport and active transport.
• Explain, with examples, passive and active transport in living organisms.

Concept Map

• Passive Transport:
  • Moves down the concentration gradient (high to low).
  • Does not require energy.
  • Types: Simple diffusion, osmosis, facilitated diffusion.
  • Facilitated diffusion uses carrier or channel proteins.
• Active Transport:
  • Moves against the concentration gradient (low to high).
  • Requires energy (ATP).
  • Uses carrier proteins.

Recap of Four Types of Transport (S.O.F.A.)

• Simple Diffusion:
  • Movement of molecules from high to low concentration through the phospholipid bilayer.
  • Examples: Lipid-soluble molecules (fatty acids, glycerol, vitamins A, D, E, K), oxygen, and carbon dioxide.
• Osmosis:
  • Diffusion of water molecules from high to low concentration through the phospholipid bilayer.
• Facilitated Diffusion:
  • Requires channel or carrier proteins.
  • Channel proteins: Transport lipid-insoluble substances like ions (calcium, chloride).
  • Carrier proteins: Transport larger molecules like amino acids and glucose by changing shape.
• Active Transport:
  • Movement from low to high concentration.
  • Requires energy (ATP) and carrier proteins.
  • Example: Transport of potassium ions into the cell via the sodium-potassium pump. The sodium-potassium pump also transports sodium ions out of the cell.

Comparing and Contrasting Passive and Active Transport (SPM Question)

• Similarities:
  • Both occur in living organisms.
  • Both involve movement of substances through a semi-permeable membrane (plasma membrane).
• Differences:

| Feature | Passive Transport .

• Concentration Gradient:
  • Passive transport: Down the concentration gradient (high to low).
  • Active transport: Against the concentration gradient (low to high).
• Energy Requirement:
  • Passive transport: No energy required.
  • Active transport: Requires energy (ATP).
• Final Outcome:
  • Passive transport: Achieves dynamic equilibrium (equal concentration).
  • Active transport: Accumulation or disposal of molecules on one side.
• Carrier Protein:
  • Simple diffusion and osmosis: Not needed.
  • Facilitated diffusion: Needed (carrier or channel protein).
  • Active transport: Needed (carrier protein).
• Examples:
  • Passive transport: Diffusion of oxygen from alveolus to blood capillaries.
  • Active transport: Absorption of mineral ions by root hair cells, transport of potassium ions into animal cells using the sodium-potassium pump.

Movement of Substances Across Plasma Membrane in Living Organisms

Passive Transport Examples

1. Gaseous Exchange in Lungs (Simple Diffusion):
   • Oxygen diffuses from alveolus (high concentration) to blood capillaries (low concentration).
   • Carbon dioxide diffuses from blood capillaries (high concentration) to alveolus (low concentration).
   • Incoming blood (pulmonary artery) is deoxygenated; outgoing blood (pulmonary veins) is oxygenated.
2. Water Absorption by Root Hair Cells (Osmosis):
   • Soil solution has higher water potential than root hair cell sap.
   • Water diffuses from soil to root hair cell down the water potential gradient.
   • Cell sap has lower water potential due to active transport of mineral ions into the vacuole.
3. Fructose Absorption in Villi (Facilitated Diffusion):
   • Fructose is transported into epithelial cells of villi with the help of transport proteins.
   • Concentration of fructose is higher in the intestinal lumen than inside the epithelial cells.
   • Fructose diffuses from the lumen into the epithelial cells down the concentration gradient with the help of a transport protein.

Active Transport Examples

1. Mineral Ion Absorption by Root Hair Cells:
   • Soil solution has lower concentration of mineral ions than root hair cell sap.
   • Mineral ions are absorbed against the concentration gradient (low to high).
   • Requires energy (ATP).
2. Absorption of Glucose and Amino Acids in Villi:
   • Requires energy (active transport).
   • Note: Fructose absorption in villi is by facilitated diffusion (passive).
3. Reabsorption of Glucose through Renal Tubules in Kidney:
   • (Mentioned for future discussion).
4. Transport of Sucrose from Leaf to Phloem Tissue:
   • (Mentioned for future discussion).

Formative Practice 3.3 (Page 64)

1. Why do hawkers spray water on fruits and vegetables?
   • To prevent wilting.
   • Water diffuses into vegetable and fruit cells by osmosis (water is hypotonic to cell sap).
   • Water is stored in vacuoles, causing them to expand.
   • Turgor pressure is created, making cells turgid and fruits/vegetables look fresh.
2. Explain what happens when sugar is sprinkled on strawberries.
   • Sugar dissolves in fluid, forming a concentrated sugar solution (hypertonic to strawberry cells).
   • Water diffuses out of strawberry cells by osmosis (from hypotonic cell sap to hypertonic sugar solution).
   • Cells become plasmolysed (cytoplasm and vacuoles shrink).
   • Strawberry tissues lose support, and the strawberry becomes soft.

Conclusion

The video provides a detailed explanation of passive and active transport, highlighting their differences, similarities, and real-world examples in living organisms. It emphasizes the importance of understanding concentration gradients, energy requirements, and the roles of various transport proteins in these processes. The examples provided, such as gas exchange in the lungs, water and mineral absorption in plants, and nutrient absorption in the small intestine, illustrate the critical roles of these transport mechanisms in maintaining life.