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7.0: Eukaryotic Cell Anatomy

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  • The cell is the basic unit of life. Based on the organization of their cellular structures, all living cells can be divided into two groups: prokaryotic and eukaryotic (also spelled procaryotic and eucaryotic). Animals, plants, fungi, protozoans, and algae all possess eukaryotic cell types. Only bacteria have prokaryotic cell types.

    Eukaryotic cells are generally much larger and more complex than prokaryotic. The larger a cell, the smaller is its surface-to-volume ratio (the surface area of a cell compared to its volume). For example, a spherical cell 2 micrometers (µm) in diameter has a surface-to-volume ratio of approximately 3:1, while a spherical cell having a diameter of 20 µm has a surface-to-volume ratio of around 0.3:1. A large surface-to-volume ratio, as seen in smaller prokaryotic cells, means that nutrients can easily and rapidly reach any part of the cells interior. However, in the larger eukaryotic cell, the limited surface area when compared to its volume means nutrients cannot rapidly diffuse to all interior parts of the cell. That is why eukaryotic cells require a variety of specialized internal organelles to carry out metabolism, provide energy, and transport chemicals throughout the cell. Both, however, must carry out the same life processes.

    Video 1: The Inner Life of a Cell. To view an excellent eight-minute animation on the inner workings of a cell created in NewTek LightWave 3D and Adobe After Effects for Harvard biology students, see . (

    We will now look at the various components and organelles found in eukaryotic cells.