Prokaryote and Eukaryote Cells

Organisms in which the nuclear material is not bounded by a definite nuclear membrane are called prokaryotes, e.g., bacteria and blue-green algae. Organisms in which the nucleus has a definite nuclear membrane are known as eukaryotes, e.g., all other plants and animals. The cells of Prokaryotes and eukaryotes differ fundamentally in many ways.

1. Nuclear membrane. As mentioned previously, prokaryotic cells lack a nuclear membrane while eukaryotic cells have a definite nuclear membrane.

2. Chromosomes. In prokaryotes the genetic material consists of nucleic acid (DNA). The DNA molecule is circular and lies in a tangled mass (nucleoid). In eukaryotes the nuclei acid (DNA) is associated with proteins to form definite bodies called chromosomes.

3. Cytoplasm Organelles. Prokaryotic cells have no endoplasmic reticulum, Golgi complex, mitochindria, lysosomes or centrioles. The enzymatic functions of the mitochondria are carried out by the cell membrane, which is folded inwards at various points. Eukaryotic cells have definite internal membrane structures like the endoplasmic reticulum, Golgi complex, mitochondria and lysosomes.

4. Cell wall. The cell wall of prokaryotes contains amino sugars and muramic acid. In eukaryotes the cell wall, when present, does not contain these substances.

5. Flagella. The flagella and cilia of eukaryotes have a definite structure consisting of 2 central and 9 peripheral fibrils. Some prokaryotes have flagella, but the flagella do not have the 9 + 2 internal structure.

6. Cytoplasmic streaming or amoeboid movement may occur in eukaryotic cells but does not occur in prokaryotes.

7. Photosynthetic apparatus. In prokaryotes chlorophyll, when present, is associated with lamellae. These lamellae are, however, not enclosed by membranes and hence no distinct chloroplasts are present. In eukaryotes, chlorophyll, when present, is found in chloroplasts.