Lecture Notes: The Cell - Basic Unit of Life

Introduction to Cells

• Cell Definition
  • Basic unit or building block of life
  • Smallest living unit of an organism
• Historical Background
  • First described by Robert Hooke in 1665
  • Described in "Micrographia" based on microscopic cork from a plant
  • Term "cell" derived from Old French "celle" and Latin "encela" meaning storeroom or chamber
• Cell Size
  • Smallest: ~2 micrometers
  • Largest: ~3 feet

Types of Cells

• Somatic Cells: Body cells
• Sex Cells: Gametes
• Eukaryotic and Prokaryotic Cells
  • Eukaryotic: With a nucleus
  • Prokaryotic: Without a nucleus
• Unicellular and Multicellular
  • Unicellular: Single cell
  • Multicellular: Many cells

Common Features of All Cells

• Cell Membrane: Separates the cell from its environment
• Cytoplasm: Jelly-like fluid containing organelles
• DNA: Contains genetic material

Eukaryotic vs. Prokaryotic

• Eukaryotic Cells
  • Presence of nucleus
  • Larger in size (10-100 micrometers)
  • Surrounded by a double membrane
  • Advanced, found in plants and animals
• Prokaryotic Cells
  • Size: ~1-10 micrometers
  • Typically unicellular (e.g., bacteria)
  • No nucleus, but a nucleoid without a nuclear membrane
  • Multiplies by fission or budding

Cell Theory

• First coined by Robert Hooke and Leeuwenhoek
• Key Points
  • All living things are made of cells
  • Cell is the basic unit of life
  • Cells arise from pre-existing cells
• Modern cell theory includes:
  • Energy of organism formed in the cell
  • Hereditary information (DNA) passed from cell to cell
  • All cells have basic chemical composition

Functions of Cells

• Absorption and Secretion
• Digestion and Movement
• Respiration and Irritability
• Biosynthesis and Homeostasis
• Excretion and Reproduction
• Egestion

Cell Organelles

• Definition: "Little organs" with unique functions
• Key Organelles
  • Cytoskeleton
  • Mitochondria
  • Ribosomes: Protein factories
  • Endoplasmic Reticulum (ER): Manufacturer
    • Rough ER: With ribosomes
    • Smooth ER: Without ribosomes
  • Golgi Complex
  • Vacuoles and Vesicles: Storage and transport
  • Lysosomes
  • Centrioles
  • Flagella and Chloroplasts

Nucleus

• Role: Command center of the cell
• Functions
  • Stores genetic code (DNA)
  • DNA dictates cell functions
  • Chromatin: Spread form of DNA
  • Chromosomes: DNA condensed during mitosis/meiosis
  • Nucleolus: Ribosome production

Endoplasmic Reticulum (ER)

• Function: Transport and synthesis of proteins
• Structure
  • Enclosed membrane structure
  • Passageway for synthesized proteins
• Ribosomes
  • Referred to as protein factories
  • Receive instructions from RNA/mRNA

Vacuoles and Vesicles

• Vacuoles
  • Large water-filled sacs
  • Storage of food and materials
• Vesicles
  • Transport proteins and materials
  • Smaller storage vehicles

This summary provides a comprehensive overview of cell biology as discussed in the lecture, highlighting vital concepts related to cell structure, function, and types.