National 4 and 5: Cells and Stem Cells

Overview

• Focus on cell biology and controversial stem cell techniques
• Debate the use of stem cells

Cells: The Building Blocks of Life

• Definition: Cells are the smallest unit of life capable of independent living
• Microscopic, require microscopes and stains (e.g., iodine) to view

Types of Cells

• Animal and Plant Cells:

  • Common structures:
    • Cytoplasm: Jelly-like, site of chemical reactions
    • Nucleus: Controls cell activities
    • Ribosomes: Site of protein synthesis
    • Mitochondria: Site of energy production
    • Cell Membrane: Controls entry and exit of substances
  • Plant Cells: Additional structures
    • Chloroplasts: Site of photosynthesis
    • Cell Wall: Provides support and structure
    • Vacuole: Stores cell sap

• Yeast Cells:

  • Common structures: Cytoplasm, ribosome, mitochondria, nucleus, cell membrane
  • Additional structures: Cell wall, sometimes vacuole

• Bacteria Cells:

  • Common structures: Ribosome, cell membrane, cytoplasm
  • Additional structure: Cell wall
  • Lacks nucleus and mitochondria; instead has plasmid (circular DNA)

Specialization of Cells

• Definition: Cells change shape to perform specific tasks
• Multicellular Organisms: Composed of tissues, tissues form organs, organs form systems
• Animal Cell Examples:
  • Red blood cells: Biconcave, carry oxygen
  • Nerve cells: Transmit impulses
• Plant Cell Examples:
  • Xylem: Transports water
  • Phloem: Transports sugars

Stem Cells

• Definition: Unspecialized cells capable of differentiating into specialized cells
• Types:
  • Embryonic Stem Cells: Found in early embryos
  • Adult Stem Cells: Found in various body tissues for growth and repair

Stem Cell Applications

• Research Uses:
  • Drug testing without animal/human trials
  • Study and fix diseases caused by faulty genes
  • Treatment of patients (e.g., burns)
• Ethical Considerations:
  • Debate on use of embryonic stem cells due to potential life destruction

Measuring Cell Size

• Field of View: Using microscopes to measure cell sizes
• Conversions: Millimeters to micrometers (1 mm = 1000 µm)

Exam Practice Tips

• Know structures present in different cell types
• Understand the functions of cell organelles
• Be familiar with cell specialization and stem cell applications

Key Takeaways

• Cells are fundamental units of life with specific structures for different functions
• Stem cells hold potential for medical advancements, with ongoing ethical debates
• Practical skills include observing cells under a microscope and calculating cell sizes

End Note: Practice essays on cell differentiation and function to reinforce learning.