Science in Action 10 - Unit C: Cycling of Matter in Living Systems

Science in Action 10 - Unit C: Cycling of Matter in Living Systems

  • Focus Areas:
    • Microscope technology
    • The cell theory
    • Cellular structures and function
    • Cellular transport
    • Specialized cells of multicellular organisms
    • Plant cell mechanisms (gas exchange, water transport)

Section 1.0: A Window to a New World (pgs. 242 – 264)

Microscope Technology

  • Light Microscopes: Tools for viewing illuminated objects using visible light.

    • Simple Microscope: One lens (like a magnifying glass).
    • Compound Microscope: Two or more lenses; invented in 1595 by Zacharias Janssen, magnifies up to 2000X.

  • Electron Microscopes: Use electron beams for illumination.

    • Types:
    • Transmission Electron Microscope (TEM): Developed in 1931; creates detailed 2D images by transmitting electrons through thin specimens.
    • Scanning Electron Microscope (SEM): Developed in the 1930s; provides 3D images by scanning surfaces with electrons.
    • Confocal Laser Scanning Microscope (CLSM): Introduced in the 1960s; generates optical slices of specimens using laser beams.
    • Scanning Tunneling Microscope (STM): Developed in mid-1900s; visualizes atoms on surfaces by creating 3D images through electron emission.
Development of the Cell Theory
  • Historical Perspectives:
    • Aristotle (384 BC – 322 BC): Proposed abiogenesis; believed specific animals arose from non-living matter (e.g., maggots from rotting meat).
    • Francesco Redi (1626 – 1697): Conducted controlled experiments showing that maggots arise from eggs laid by flies, not spontaneously from meat.
    • Louis Pasteur (1822 – 1895): Settled the debate using his experiment with swan-neck flasks, supporting biogenesis—the idea that life comes from pre-existing life.
Key Elements of Cell Theory:
  1. All organisms are composed of one or more cells.
  2. The cell is the smallest functional unit of life.
  3. All cells arise from pre-existing cells.
Microscopic Discoveries
  • Robert Hooke (1635 – 1703): First to observe and coin the term "cells" from cork.
  • Antony van Leeuwenhoek (1632 – 1723): Described single-celled organisms using single lens microscopes.
  • Schleiden and Schwann: Declared that all living organisms consist of cells; early proponents of cell theory.
  • Rudolf Virchow: Proposed that all cells arise from other cells.

Section 2.0: What’s in a Cell? (pgs. 266 – 293)

Cellular Functions
  • Cells sustain life by:
    1. Obtaining food and energy
    2. Converting energy (e.g., photosynthesis)
    3. Constructing and maintaining cellular structures
    4. Carrying out chemical reactions
    5. Eliminating waste
    6. Reproducing
Cell Types
  • Prokaryotes: Single-celled organisms lacking a nucleus; examples include bacteria and algae.
  • Eukaryotes: More complex cells with a nucleus; examples include plant and animal cells.
Organelles
  1. Cell membrane: Protective barrier; facilitates material transport.
  2. Vesicles: Store or transport materials.
  3. Cytoplasm: Jelly-like fluid containing organelles; about 70% water.
  4. Nucleus: Contains DNA; directs cellular activities.
  5. Ribosomes: Sites of protein synthesis.
  6. Endoplasmic Reticulum (ER):
    • Rough ER: Has ribosomes; processes proteins.
    • Smooth ER: No ribosomes; synthesizes lipids.
  7. Lysosomes: Contain enzymes for digestion.
  8. Golgi Apparatus: Modifies and packages proteins.
  9. Mitochondria: Powerhouse of the cell; involved in ATP production (cellular respiration).
  10. Vacuoles: Storage for nutrients and waste.
  11. Cell Wall: Provides structure and protection in plant cells.
  12. Chloroplasts: Sites of photosynthesis in plant cells.
Cellular Transport Mechanisms
  • Cell Membrane: Regulates what enters and exits the cell; described by the fluid mosaic model.
  • Transport Types:
    • Passive Transport: No energy required (e.g., diffusion, osmosis).
Types of Solutions in Osmosis:

  • Hypotonic: Lower solute concentration outside. Water enters cell; may burst.

  • Hypertonic: Higher solute concentration outside. Water leaves; cell shrinks.

  • Isotonic: Equal solute concentration; maintains equilibrium.

  • Active Transport: Requires energy to move substances against a gradient.

  • Bulk Transport: Movement of large molecules via vesicles (endocytosis and exocytosis).

Applications in Industry and Medicine
  • Reverse Osmosis: Water purification process.
  • Kidney Dialysis: Filters blood; retains necessary materials while removing waste.
  • Controlled Drug Delivery: Uses liposomes to transport medications safely.
The Ratio of Surface Area to Volume
  • As cells grow, volume increases faster than surface area, affecting nutrient and waste exchange efficiency.
  • This ratio impacts cellular function and viability.