The Cell Bio 101

Cell Definition

• A cell is the basic unit of biological activity, bounded by a membrane, capable of independent reproduction.
• Organisms are unicellular or multicellular, all composed of cells.

Cell Theory

• Robert Hooke (1665): First observed dead cells; coined the term "cell."
• Mathias Schleiden (1838): All plant tissues are made of cells.
• Theodor Schwann (1839): Described similarities between plant and animal cells.
• Rudolf Virchow: Cells arise only from pre-existing cells.

Cell Structure and Components

• Plasma Membrane:

  • Encloses the cell, regulates material flow.
  • Involved in communication and modified in some cells to form microvilli.

• Endoplasmic Reticulum (ER):

  • Network of membrane-enclosed spaces; consists of rough (with ribosomes) and smooth types.
  • Functions in transport, storage, and protein synthesis.

• Golgi Complex:

  • Stack of membranes for storage, modification, and packaging of proteins; forms lysosomes.

• Mitochondria:

  • Powerhouses of the cell; double membrane structure, site of ATP production.
  • Self-replicating organelles.

• Chloroplasts:

  • Found in plants; sites of photosynthesis, contain chlorophyll.
  • Surrounded by two membranes, includes stroma and grana.

• Vacuoles:

  • Fluid-filled spaces; larger in plant cells, important for turgidity.

• Microtubules and Microfilaments:

  • Rod-like structures for cellular movement and shape.

• Centrioles, Cilia, Flagella:

  • Centrioles assist in cell division; cilia and flagella aid in movement.

• Nucleus:

  • Large structure containing genetic material; involved in cell growth and activity regulation.
  • Contains chromatin and nucleoli for ribosomal RNA synthesis.

Prokaryotic vs. Eukaryotic Cells

• Prokaryotic Cells:
  • Simple, smaller (0.1 to 0.25 cm), DNA not in a membrane, no membrane-bound organelles.
• Eukaryotic Cells:
  • Larger, complex structures (10-100 cm), contain a nucleus and membrane-bound organelles.

Key Differences Between Prokaryotic and Eukaryotic Cells

Differences Between Plant and Animal Cells