ICSE 6 Biology Cell Basic

headphones Listen to this note:
Speed: 1.0x

Table of Contents

    The Cell

    The Building Block of Life

    1.0 Introduction to the Cell

    A cell is the most basic structural and functional unit of all living organisms. Just as a building is made of bricks, every living thing—from a tiny bacterium to a giant whale—is made of cells.

    1.1 Discovery & Study

    • Robert Hooke (1665): The first person to see cells. He looked at a thin slice of cork (dead bark) and noticed small "rooms" which he called cells.
    • Modern Study: With the invention of the Electron Microscope, scientists can now see the tiny parts inside a cell, called organelles.

    1.2 The Cell Theory

    Formulated by Schleiden, Schwann, and Virchow, this theory has three main pillars:

    1. All living organisms are composed of one or more cells.
    2. The cell is the basic unit of structure and function in organisms.
    3. New cells are produced from existing cells.

    2.0 The Microscope: Seeing the Invisible

    Since cells are microscopic, we need tools to magnify them.

    [attachment_0](attachment)
    • Compound Microscope: Uses light and glass lenses. (Total Magnification = Eyepiece × Objective).
    • Electron Microscope: Uses beams of electrons to provide much higher magnification (up to 500,000x).

    3.0 Variations in Cells

    3.1 Number and Type

    • Unicellular: Single cell (e.g., Amoeba).
    • Multicellular: Millions of cells (e.g., Humans).
    • Prokaryotic: Simple cells without a defined nucleus.
    • Eukaryotic: Complex cells with a well-defined nucleus.

    3.2 Shape and Size

    Shapes: Nerve Cells (Long), Muscle Cells (Spindle), WBCs (Irregular).

    Sizes: Tiny bacteria (0.1 Ξm) to the massive Ostrich egg (170 mm).

    4.0 Anatomy of a Cell

    Every cell generally has three main parts:

    • Cell Membrane: Selectively permeable outer layer.
    • Cell Wall (Plants Only): Rigid outer layer for protection.
    • The Nucleus: The "Control Center" containing genetic material.
    • Cytoplasm: Jelly-like fluid filling the cell.

    5.0 Cell Organelles: The "Little Organs"

    • ⚡ Mitochondria: The Powerhouse (Creates energy).
    • 🏭 Ribosomes: Protein Factories.
    • ðŸģ Chloroplasts (Plants Only): The Kitchen (Photosynthesis).
    • 🚛 ER: Transport System.
    • ðŸ“Ķ Golgi Apparatus: The Post Office.
    • 🗄️ Vacuoles: Storehouse (Large in plants).
    • ⚠️ Lysosomes: Suicide Bags (Digests waste).

    6.0 Plant Cell vs. Animal Cell

    Feature Plant Cell Animal Cell
    Cell Wall Present Absent
    Plastids Present Absent
    Vacuoles One Large, Central Many Small
    Centrosome Absent Present
    Older Posts