Prokaryotic Cells
These are cells which have no true nucleus. The term prokaryotic derived from two Greek words which are Pro means before and Karyo means nucleus.
Therefore the term prokaryotic means not true cells. Therefore prokaryotic cells or Bacteria cells are not true cells because has no membrane which bound the nuclear materials. Prokaryotic cells include the bacteria cells and blue or green algae cells.
1.1.1. Characteristics of Prokaryotic Cells
· Prokaryotes lack an organized nucleus (Nucleus with nuclear membrane)
· They lack membrane-bound organelles example mitochondria and chloroplasts.
· They possess necked DNA which is found in a central part of the cell called the nucleoid.
· The cell wall of a prokaryote acts as an extra layer of protection, helps maintain cell shape, and prevents dehydration.
· Prokaryotic cell size ranges from 0.1 to 5.0 nm in diameter.
· The small size of prokaryotes allows quick entry and diffusion of ions and molecules to other parts of the cell while also allowing fast removal of waste products out of the cell.
· Their cells have few organelles
Reflection Question 01
Bacteria cell is not a true cell. Explain why
1.1.2. Structure of Prokaryotic Cell
Structurally a prokaryotic cell is very small with average diameter 0.5-110nm. It is enclosed with a cell wall outside and the cell surface membrane inside. There is a capsule or a slime coat which surrounded the cell layer which protects the bacteria cell. There is a cell wall which composed of murein or peptoglycan. The cell wall provides the rigidity which results to the bacteria to have a definite shape. The cell also consists of the cell surface membrane which allows the movement of materials in and out of the cell. The membrane is also folded to form structures like Mesosome which is responsible for respiration, photosynthetic membrane and nitrogen fixation membrane.
The cytoplasm is enclosed in the cell surface membrane. The cytoplasm consist of circular DNA which lack the protein coat called Histone. Another DNA having the structure called plasmid may be present, ribosomes of small size 70’s, food granules and plasmid. There is flagellum for locomotion and also there are pills or pillus which is used for asexual reproduction.
Test your understanding
Question 01
a. State the components of the cell theory
b. Using the rod shaped Bacterium as your example, describe the typical prokaryotic cell.
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Image credit: simple.wikipedia.org