Introduction to Biology and Cell Theory

Oct 25, 2024

Biology Lecture Notes

Introduction to Biology

  • Biology integrates perspectives from physics and chemistry to understand life.
  • The foundational unit of life is the cell.

Cell Theory

  1. All living things are composed of cells.
    • Living entities contain identifiable cells or cell-like structures.
  2. Cells are the smallest unit of life.
    • Subcellular components are not considered alive.
  3. Cells arise from pre-existing cells.
    • This concept involves cell division and is supported by extensive data.

Exceptions to Cell Theory

  • Striated Muscle Fibers
    • Composed of fused cells, containing multiple nuclei, functioning as a single unit.
  • Giant Algae
    • A single cell can grow extremely large, challenging the notion of large organism composition.

Functions of Life

  • Reproduction
  • Metabolism
  • Responsiveness/Sensitivity
  • Homeostasis
  • Growth
  • Excretion
  • Nutrition

Example: Paramecium

  • Performs all life functions including movement, growth, asexual reproduction, and metabolic processes.

Cell Growth and Size Limitation

  • Surface Area to Volume Ratio
    • Cells must maintain a certain ratio to survive.
    • Cell Division: helps maintain this ratio by creating smaller cells.

Cell Magnification

  • Equation: Magnification (M) = Image Size / Actual Size
  • Important to convert measurements to the same units (e.g., micrometers).

Magnification Practice Problem

  • Actual size: 100 micrometers; Image size: 3 cm.
  • Conversion: 100 micrometers = 0.01 cm.
  • Magnification = 3 cm / 0.01 cm = 300x.

Multicellular Organisms

  • Composed of multiple cells working together creating emergent properties.
  • Cell Differentiation
    • Genes are expressed to form specialized cells (e.g., nerve, muscle, endothelial).

Stem Cells

  • Definition: Undifferentiated cells that can become specialized.
  • Sources: Can be derived from embryos or adult tissues.
  • Applications and Ethical Issues
    • Therapies: Can generate tissues for treatments (e.g., burn healing).
    • Ethical Concerns: Extraction from embryos can lead to destruction of potential life.

Stem Cell Therapy: Stargardt's Disease

  • Condition: Genetic mutation causing blindness.
  • Treatment: Use of stem cells to create healthy photoreceptors replacing damaged ones.