What Are Living Organisms Made Up Of?

Key Notes:

Cells: The Basic Unit of Life

  • All living organisms are made up of cells.
  • Cells are the smallest structural and functional units of life.
  • Organisms can be:
    • Unicellular: Made up of a single cell (e.g., Amoeba, Paramecium).
    • Multicellular: Made up of multiple cells (e.g., humans, plants).

Components of a Cell

  • Plasma Membrane: The outermost layer that controls the movement of substances in and out of the cell.
  • Cytoplasm: A jelly-like substance where most cellular activities occur.
  • Nucleus: The control center of the cell, containing DNA (genetic material).
  • Organelles: Specialized structures within the cell, such as mitochondria, ribosomes, and chloroplasts (in plants).

Cell Types

  • Prokaryotic Cells: Simple cells without a defined nucleus (e.g., bacteria).
  • Eukaryotic Cells: Complex cells with a well-defined nucleus and organelles (e.g., plant and animal cells).

Tissues and Organs

  • Similar cells group together to form tissues.
  • Tissues combine to form organs, which perform specific functions (e.g., the heart, brain, leaves).
  • Organs work together to form organ systems.

Biomolecules: Building Blocks of Life

  • Cells are composed of essential biomolecules:
    • Proteins: For structure and function (e.g., enzymes, hormones).
    • Carbohydrates: For energy storage and supply (e.g., glucose, starch).
    • Lipids: For energy storage and forming cell membranes.
    • Nucleic Acids: DNA and RNA, responsible for genetic information.
    • Water: Constitutes 70-90% of the cell’s composition, vital for chemical reactions.

Cell Division

  • Cells multiply through processes like mitosis (for growth and repair) and meiosis (for reproduction).

Hierarchy of Biological Organization

  • Cell → Tissue → Organ → Organ System → Organism.
  • This organization ensures efficient functioning of living organisms.

Specialization of Cells

  • In multicellular organisms, cells specialize to perform specific tasks (e.g., nerve cells, red blood cells, muscle cells).

Plant vs. Animal Cells

  • Plant cells have additional features like a cell wall, chloroplasts, and a large vacuole.
  • Animal cells lack a cell wall and chloroplasts but have centrioles.

Role of DNA

  • DNA (Deoxyribonucleic Acid) contains instructions for the structure, function, and reproduction of cells.
  • It is housed in the nucleus and determines hereditary traits.

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