Fundamental Unit of Life Summary

Page 1

  • Robert Hooke's Observation (1665):

    • Observed cork under a microscope, noticed honeycomb-like structures called cells (Latin for 'little room').
    • Importance: First known observation of cells, marking the foundation for cell biology.

  • Activity 5.1: Preparation of Onion Peel Slide:

    • Peel off a piece of onion epidermis, place on slide with water and safranin, and observe under a microscope.

Page 2

  • Types of Organisms:

    • Unicellular organisms: Made of a single cell (e.g. Chlamydomonas, Paramecium).
    • Multicellular organisms: Composed of many cells (e.g. plants, animals).

  • Key Concepts:

    • All cells come from pre-existing cells through division.
    • Activity 5.2: Observe variations in plant cells from different parts.

  • Historical Discoveries:

    • Leeuwenhoek observed free-living cells (1674).
    • Brown discovered the nucleus (1831).

Page 3

  • Cell Characteristics:

    • Shape and size relate to function; example: nerve cells have unique shapes.
    • Division of labor exists in multicellular organisms and also within individual cells (organelles).

  • Key Questions:

    1. Who discovered cells? Robert Hooke.
    2. Why is the cell termed the unit of life? It performs all life processes.

  • Cellular Composition:

    • Three main structures in cells: Plasma membrane, nucleus, cytoplasm.

Page 4

  • Plasma Membrane:

    • Outermost cell covering, selectively permeable, regulates entry & exit of materials (diffusion & osmosis).

  • Types of Solutions:

    1. Hypotonic: Cell swells as water enters.
    2. Isotonic: No net movement of water.
    3. Hypertonic: Cell shrinks as water exits.

Page 5

  • Cell Wall:

    • Present in plant cells, provides structure and protection, composed of cellulose.

  • Nucleus:

    • Contains DNA, surrounded by a nuclear membrane; controls cell activity and heredity.

  • Prokaryotes vs Eukaryotes:

    • Prokaryotes: No nuclear membrane, simpler structure; Eukaryotes: Defined nucleus, complex organelles.

Page 6

  • Cytoplasm:

    • Fluid inside cells, where organelles are found.

  • Cell Organelles:

    • Endoplasmic Reticulum (RER/SER), Golgi Apparatus, Lysosomes, Mitochondria, Plastids.

Page 7

  • Lysosomes:

    • Digestive enzymes within the cell, involved in waste disposal.

  • Mitochondria:

    • Energy production (ATP), considered the powerhouse of the cell.

  • Plastids:

    • Found only in plant cells; include chloroplasts for photosynthesis.

Page 8

  • Vacuoles:
    • Storage sacs, larger in plant cells (maintain turgidity), involved in storage and waste management.

Page 9

  • Importance of Organization:
    • Structure of the cell and organelles enable functions like respiration, nutrition uptake, waste clearance, and growth.

Page 10

  • Cell Division:

    • Mitosis: Growth & tissue repair; Meiosis: Gamete formation.

  • Key Takeaways:

    • Fundamental unit of life is the cell.
    • Cell structure ensures it can perform essential functions like nutrient absorption and waste removal.