Discovery Science: Earth – Differences – Plant and Animal Cells

Earth Science: Differences – Plant and Animal Cells

The eukaryotic cells of both plants and animals have a complex internal structure. Plant cells, however, tend to be significantly larger, and they have typical characteristics that make them easy to identify.

The disk-shaped structures called plastids are unique to plant cells. Even fungi, which were once grouped among the plants, lack these special organelles. Plastids include the green chloroplasts that carry out photosynthesis in a plant’s stems and leaves, as well as chromoplasts, which color flowers and fruits such as tomatoes and peppers.

Colorless leucoplasts store nutrients, such as the starch in a potato.

Vacuoles and cell walls

Even under a simple light microscope, a plant cell’s central vacuole is especially striking to the eye, since it makes up most of the cell’s volume. Its liquid interior contains substances such as flower pigments, nutrients, ions, and defensive chemicals, to ward off insects, for instance. The vacuole also holds numerous enzymes, and thus it handles digestion within the cell; in animal cells, this is carried out by lysosomes.

Since it is filled with liquid the central vacuole creates internal pressure that would cause the cell to burst without equivalent counter- pressure. Thus plant cells need a strong, stable protective shell: the cell wall. The cell wall lies directly outside the cell membrane. It contains countless intertwined strands of cellulose, a molecule composed of chains of up to 10,000 carbohydrate units.

Along with other materials, the cellulose gives the cell wall enormous strength to resist inner or outer pressure. Since the plant’s cell walls are connected to each other, they provide a kind of “skeleton” that gives shape to the plant. The cell wall space also contains signal molecules and defensive substances, which help protect the plant tissue, for instance, from attacks by insects or fungi.

The cell wall is also penetrated by very fine plasmatic tubes, which connect the living cytoplasm of different cells. These tubes, so-called plasmodesmata, transport nutrients and allow communication among the various cells and tissues.


Many plants absorb harmful sub-stances from the environment through their roots and leaves, such as salts, heavy metals, and pesticides. These substances are not only toxic to humans and animals, but can also interfere with plant metabolism.

Plants, how-ever, have no liver or kidneys to help them isolate and remove poisons. Therefore they must carry out intracellular detoxification: special transport molecules carry the poisons into the large central vacuole, where they are stored or chemically deactivated.


AVERAGE CELL SIZES in animals, 8-20 micrometers, in plants, 100-300 micrometers (1 micrometer = 1/1000 millimeter)

A LIVER CELL contains from 500 to 2,000 mitochondria, averaging 0.5-1 micrometer each.