In-depth Notes on the Cycling of Matter in Living Systems

Science in Action 10: Cycling of Matter in Living Systems

Overview of Unit C
  • Topics covered in this unit:
    • Microscope technology
    • Cell theory
    • Cellular structures and functions
    • Cellular transport
    • Specialized cells in multicellular organisms
    • Mechanisms in plant cells (gas exchange, water transport)
Section 1.0: A Window to a New World (pgs. 242-264)
A. Light Microscopes
  • Light Microscopes: Illuminate objects with visible light
    • Simple Microscope: Single lens, similar to a magnifying glass.
    • Compound Microscope: Combines two or more lenses; first made by Zacharias Janssen (1595).
    • Magnification: Up to 2000X.
B. Electron Microscopes
  • Uses a beam of electrons for illumination.
  • Types and features:
    • TEM (Transmission Electron Microscope):
    • Invented in 1931.
    • Specimens are thinly sliced and placed in a vacuum.
    • Produces 2-D images, viewing internal structures.
    • SEM (Scanning Electron Microscope):
    • Developed in the 1930s.
    • Produces 3-D images by scanning surfaces.
    • CLSM (Confocal Laser Scanning Microscope):
    • Uses lasers to create optical slices that are later stitched together.
    • STM (Scanning Tunneling Microscope):
    • Developed mid-1900s; images atoms on surfaces (e.g., DNA).
Development of the Cell Theory
A. Historical Perspectives
  • Aristotle (384 – 322 BC): Proposed abiogenesis, no scientific tests; examples included:
    • Eels from river mud, rats from garbage, frogs from mud.
  • Francesco Redi (1626 – 1697): Controlled experiments refuted abiogenesis:
    • Experiment:
    • Jar with meat uncovered → maggots appeared.
    • Jar with covered meat → no maggots.
  • Louis Pasteur (1822 – 1895): Confirmed biogenesis:
    • Experiment:
    • Nutrient broth in swan-neck flask; boiled to kill microbes.
    • Broth remained clear; became cloudy when tipped.
B. Establishment of Modern Cell Theory
  • Modern Cell Theory includes:
    1. All organisms are composed of one or more cells.
    2. Cells are the smallest functional unit of life.
    3. All cells come from pre-existing cells.
Discovering Cells
  • The microscope allowed the discovery of cells and microscopic life.
  • Cell: Smallest functional unit of life, fundamental to all living organisms.
  • Robert Hooke: First to see and name "cells" (from cork).
  • Antony van Leeuwenhoek: Described single-celled organisms (500X magnification).
Cell Research at the Molecular Level
Genes and Cancer
  • Genes: DNA segments directing cell activities; mutations can lead to diseases (e.g., cancer).
  • Human Genome Project (HGP): Sequenced human genes (30,000 to 40,000).
  • Gene therapy can correct genetic disorders.
Section 2.0: What’s in a Cell? (pgs. 266-293)
A. Functions of Cells
  • Essential functions include:
    • Obtaining energy, converting energy, and eliminating waste.
B. Types of Cells
  1. Prokaryotic Cells: One-celled, no nucleus (e.g., bacteria).*
  2. Eukaryotic Cells: More complex with nucleus (most plant/animal cells).
Organelles and Their Functions
  1. Cell Membrane: Protective barrier; regulates material transport.
  2. Cytoplasm: Gel-like fluid, provides support to organelles.
  3. Nucleus: Contains DNA; controls cell activities.
  4. Ribosomes: Site of protein synthesis.
  5. Mitochondria: Energy conversion via cellular respiration.
    • Formula C<em>6H</em>12O<em>6+6O</em>2<br/>ightarrow6CO<em>2+6H</em>2O+extenergyC<em>6H</em>{12}O<em>6 + 6O</em>2 <br /> ightarrow 6CO<em>2 + 6H</em>2O + ext{energy}
  6. Chloroplasts: Site of photosynthesis (in plants) - converts sunlight into energy (6CO<em>2+6H</em>2O<br/>ightarrowC<em>6H</em>12O<em>6+6O</em>26CO<em>2 + 6H</em>2O <br /> ightarrow C<em>6H</em>{12}O<em>6 + 6O</em>2).
Cell Membrane Structure and Function
  • Phospholipid Bilayer: Hydrophilic heads and hydrophobic tails.
  • Proteins: Facilitate functions like transport and chemical reactions.
Transport Across Cell Membranes
  • Passive Transport: Movement without energy (e.g., diffusion).
  • Active Transport: Movement against concentration gradient requiring ATP.
  • Bulk Transport: Movement of large substances via vesicles (endocytosis and exocytosis).
Applications of Cellular Transport
  1. Reverse Osmosis: Water purification by filtering contaminants.
  2. Kidney Dialysis: Filters blood while retaining necessary substances.
  3. Controlled Medication Delivery: Liposomes transport drugs safely.
Function and Limitations of Cell Size
  • Surface area-to-volume ratio impacts nutrient and waste exchange.
  • Larger cells may experience inefficiencies in transport; critical for maintaining homeostasis in the body.