Animal

  • Key Question: What features characterize animal cells?

  • Shape:

    • Animal cells do not have a regular shape unlike plant cells, which have a rigid cell wall.
    • Many animal cells can alter their shape for functions like engulfing foreign material (e.g., phagocytes).

  • Size:

    • Typical diameter of animal cells ranges from 30-150 µm.

  • Organelles:

    • Nucleus:
    • Contains the nucleolus, which is involved in ribosome synthesis.
    • Nuclear pores allow communication with the cytoplasm.
    • Encased in a double-layered nuclear membrane.
    • Ribosomes:
    • 80S ribosomes, may be free in cytoplasm or attached to the rough endoplasmic reticulum (ER).
    • Endoplasmic Reticulum (ER):
    • Rough ER: Site of protein synthesis and new membrane synthesis.
    • Smooth ER: Functions in lipid and carbohydrate metabolism, including detoxification and hormone synthesis.
    • Lysosomes:
    • Small garbage sacs (0.5-1.0 µm) containing enzymes that break down food and foreign material.
    • Golgi Apparatus:
    • Series of disc-shaped sacs that modify, package, and send proteins to their correct destinations.
    • Mitochondria:
    • Double membrane-bound organelles that produce ATP; number varies based on cell's energy requirements.
    • Centrioles:
    • Associated with nuclear division, composed of microtubules, and absent in higher plant cells.
    • Vacuoles:
    • Smaller than plant vacuoles, involved in transport via exocytosis and endocytosis.

  • Differences Between Plant and Animal Vacuoles:

    • Plant: Large, primarily for water storage.
    • Animal: Small, primarily for transport of substances.

  • Unique Animal Cells Feature:

    • Centrioles: Present in animal cells, involved in cell division, absent from plant cells.