TYPES OF CELL
Generally cells are classified into two types. First one is Prokaryotic cell .It has No true nucleus consisting of no nuclear membrane. Another one is Eukaryotic cell. It has True nucleus consisting of nuclear membrane.
1. Prokaryotic cell
The unicelluar organisms like Bacteria has Prokaryotic cells. It has No true nucleus. This type of nucleus is called as nucleiod. No nuclear membrane is around this nucleiod. These cells were the first form of life on earth. It is ranging from 0.003 to 2.0 micro meter in diameter.
Eg. Eschericia coil bacteria
2. Eukaryotic cell
Cells which has true nucleus is called as eukaryotic cell. It is bigger than prokaryotic cells. It’s organelles bounded by membrane.
Ex. Plants,animals, most of the fungi and algae.
Aim: To observe onion peel cells under a microscope
Materials Required: Glass slide, cover slip, onion, iodine solution, knife and microscope.
Procedure: Take an onion and cut it into two halves along its length. Take out one of its fleshy leaves. With the help of a pair of forceps, remove a transparent, thin peel from the inner surface of the leaf. Take a glass slide and put a drop of water at the centre. Place the peel on the drop of water. Pour a drop of iodine solution on the peel. Now place a cover slip over the material. Observe under the microscope.
Observation: You will be able to see rectangular cells of the onion peel, with a nucleus in each of them.
Differences between Prokaryotic cell Eukaryotic cell
• It’s diameter ranges from 1 to 2 micron
• Absence of membrane bound organelles
• Nucleus consisting of no nuclear membrane
• Absence of nucleoli
• It’s diameter ranges from 10 t0 100 micron
• Presence of membrane bound organelles
• True nucleus consisting of nuclear membrane
• Presence of nucleoli