Lecture: The Fundamental Unit of Life

Introduction

• Presented by: Ankita
• Chapter: Fundamental Unit of Life (Class 9 Biology)
• Objective: Cover the whole chapter in 15 minutes

Cell History

• First cell discovered: Robert Hooke, 1665 (dead cell)
• First living cell discovered: Antonie van Leeuwenhoek

Cell Theory

• Scientists: Schleiden, Schwann, Rudolf Virchow
• Postulates:
  1. All living organisms are made up of cells
  2. Cells are the structural and functional unit of life
  3. All cells arise from pre-existing cells

Importance and Functions of Cells

• Functions: Nutrition, energy production, waste removal, series of biochemical reactions
• Reason for being structural & functional unit: Cells perform essential functions that make life possible

Types of Organisms

• Unicellular: Single cell, e.g., Amoeba
• Multicellular: Multiple cells, e.g., Humans
• Hierarchy: Cells → Tissues → Organs → Organ systems → Organism

Types of Cells

• Prokaryotic Cells: No membrane-bound genetic material, e.g., Bacteria
• Eukaryotic Cells: Membrane-bound genetic material, e.g., Plants, Animals

Cell Components

Cell Membrane

• Function: Separates internal environment, aids in transport
• Transport Types:
  • Active Transport: Requires energy
  • Passive Transport: No energy required
    • Diffusion: Movement of molecules from high to low concentration (liquid/gas)
    • Osmosis: Movement of water from high to low concentration through semi-permeable membrane
• Solutions & Effects:
  • Hypertonic: Cell shrinks, water moves out
  • Hypotonic: Cell swells, water moves in
  • Isotonic: Equal movement of molecules

Cytoplasm

• Description: Jelly-like fluid with cell organelles
• Function: Biochemical reactions

Nucleus

• Role: Control center of the cell
• Components:
  • Nuclear membrane/envelope
  • Nucleoplasm
  • Nucleolus (synthesis of RNA and ribosomes)
  • Chromatin (DNA and protein), forms chromosomes during cell division
• DNA: Deoxyribonucleic acid, genetic material

Mitochondria

• Role: Powerhouse, ATP synthesis (energy currency of the cell)
• Features: Double membrane, own DNA and ribosomes

Endoplasmic Reticulum (ER)

• Types:
  • Rough ER: With ribosomes, synthesizes proteins
  • Smooth ER: No ribosomes, synthesizes lipids
• Function: Membrane biogenesis (formation of plasma membrane)

Golgi Apparatus

• Role: Postman of the cell, modifies, sorts, and packages proteins and lipids from ER

Lysosomes

• Role: Digestive sacs, contain digestive enzymes
• Function: Break down cellular waste and non-functional organelles, called ‘suicide bags’

Plastids

• Types: Chloroplasts (green pigment), Chromoplasts (red, yellow pigments), Leucoplasts (storage)
• Function: Photosynthesis (chloroplasts), storage (leucoplasts)

Vacuole

• Function: Storage sac
• Size: Large in plant cells, small in animal cells

Cell Wall

• Presence: Only in plant cells
• Properties: Freely permeable, rigid, provides structural support

Cell Division

• Mitosis: Producing identical daughter cells (growth, repair)
• Meiosis: Producing gametes with half the number of chromosomes (reproduction)

Conclusion

• Summary of chapter, highlighting major points covered
• Encourage students to like, subscribe, and comment