UNIT 3: Biology Overview

  • Definition of Biology: Study of living organisms.
  • Diversity vs. Unity:
    • Descriptive taxonomy highlights diversity.
    • Cell Theory: Emphasizes a unified cellular organization in all life forms.
    • Provides framework for understanding physiological and behavioral processes.
  • Cell Structure and Growth:
    • Overview on cellular organization provided in chapters.
    • Discussion of cell growth through division.

Physico-Chemical Approach to Biology

  • Understanding Living Phenomena:
    • Use of a physico-chemical approach to study physiological and behavioral processes.
    • Investigation through cell-free systems enables molecular description of biological processes.
  • Analysis of Living Tissues:
    • Identifies elements and compounds in living organisms.
    • Raises the question of the functions of these organic compounds in cellular activities.
  • Molecular Basis of Physiological Processes:
    • Addresses functions like digestion, excretion, memory, defense, recognition, etc.
    • Explains abnormal processes in diseases.
  • Term: This approach to biology is known as Reductionist Biology.
    • Involves applying concepts and techniques from physics and chemistry to biology.

Chapters Overview

  • Chapter 8: Cell as the Unit of Life
  • Chapter 9: Introduction to various biomolecules
  • Chapter 10: Focus on cell cycle and division

G.N. Ramachandran: Contributions to Structural Biology

  • Overview of Ramachandran:
    • Key figure in protein structure and leader of the Madras School of conformational analysis of biopolymers.
    • Key Contributions:
    • Discovery of the triple helical structure of collagen in 1954.
    • Development of the Ramachandran plot for analyzing protein conformations.
  • Biography:
    • Born on October 8, 1922, near Cochin, India.
    • Influenced by his father, a mathematics professor.
    • Top-ranking student in B.Sc. (Honors) Physics at University of Madras in 1942.
    • Earned Ph.D. from Cambridge University in 1949, mentored by Linus Pauling.
    • Passed away at the age of 78 on April 7, 2001.

Understanding Cells

  • Distinction between Living and Non-living:
    • Living organisms possess cells, while non-living things do not.
  • Types of Organisms:
    • Unicellular Organisms:
    • Comprised of a single cell capable of independent existence and essential life functions.
    • Multicellular Organisms:
    • Composed of many cells (e.g., humans).
  • Definition of a Cell:
    • Fundamental structural and functional unit of all living organisms.
  • Historical Contributions:
    • Antonie Von Leeuwenhoek: First to observe and describe live cells.
    • Robert Brown: Discovered the nucleus.
    • Advancements in microscopy gave rise to detailed cellular structures (electron microscope).

Cell Theory

  • Foundations of Cell Theory:
    • Matthias Schleiden (1838):
    • Observed that all plants consist of different cell types forming plant tissues.
    • Theodor Schwann (1839):
    • Studied animal cells, noted presence of plasma membrane and cell wall unique to plant cells.
    • Contributions to Cell Theory:
    • Suggested that organism bodies consist of cells/products of cells.
  • Rudolf Virchow (1855):
    • Clarified that new cells arise from pre-existing cells, encapsulated in the phrase “Omnis cellula-e cellula.”
  • Cell Theory Today:
    • (i) All living organisms are made of cells and their products.
    • (ii) All cells derive from pre-existing cells.

Overview of Cell Structure

  • Cell Observation:
    • Observed under a microscope (e.g., onion peel, human cheek cells).
  • Typical Plant Cell Structure:
    • Distinct cell wall as the outer boundary.
    • Presence of cell membrane within the wall.
  • Human Cheek Cells:
    • Possess an outer membrane as the boundary.
  • Cell Nucleus:
    • Dense membrane-bound structure housing chromosomes, which contain DNA.