Cell Biology – Cytology
Cell is the basic functional and structural unit of life. Anton Von Leuwenhoek first saw and described a cell. Robert brown later discovered the nucleus of a cell.
- Smallest cell - Mycoplasma
- Largest cell – Egg of an Ostrich
- Longest cell – Nerve cell
- Typical Plant cell – Onion cell
Types of cell
Cells are of two types:
- Prokaryotic : In this type of cell Nucleus and organelles are not present
- Eukaryotic: In this type of cell Nucleus and organelles are present
Ribosomes are the protein builders or the protein synthesizers of the cell. Ribosomes are found in both prokaryotes and eukaryotes. Ribosomes can be found floating within the cytoplasm or attached to the endoplasmic reticulum.
Endoplasmic reticulum are used to transfer, synthesis and modification of proteins. These are of two types
- Rough endoplasmic reticulum: These are rough in shape due to ribosomes are attached to its outer (cytoplasmic) surface. Rough ER lies immediately adjacent to the cell nucleus. Its main work is protein synthsesis.
- Smooth endoplasmic reticulum: The smooth ER is involved in the synthesis of lipids, including cholesterol and phospholipids, which are used in the production of new cellular membrane. In certain cell types, smooth ER plays an important role in the synthesis of steroid hormones from cholesterol. In cells of the liver, it contributes to the detoxification of drugs and harmful chemicals.
These are the powerhouse of the cell. They act like a digestive system which takes in nutrients, breaks them down, and creates energy rich molecules for the cell. The biochemical processes of the cell are known as cellular respiration. Many of the reactions involved in cellular respiration happen in the mitochondria. Mitochondria keep the cell full of energy.
These are the suicidal bags of the cell. lysosomes can be found in nearly every animal-like eukaryotic cell. Lysosomes hold enzymes that were created by the cell. The purpose of the lysosome is to digest things. They might be used to digest food or break down the cell when it dies.
Plastids are major organelles found in the cells of plants and algae. Plastids are the site of manufacture and storage of important chemical compounds used by the cell. Plastids often contain pigments used in photosynthesis, and the types of pigments present can change or determine the cell's colour. Plastids are responsible for the colour of Plants
Cilia and flagella
These are the structures which help in the movement of cell. Cilia are short and there are usually many (hundreds) cilia per cell. On the other hand, flagella are longer and there are fewer flagella per cell (usually one to eight).
The cell nucleus is a membrane bound structure that contains the cell's hereditary information and controls the cell's growth and reproduction. It is the command center of a eukaryotic cell and is commonly the most prominent organelle in a cell. Nucleus contains genetic material i.e DNA, Chromosomes.