The main chemical components of ribosomes are protein and RNA. The ratio of protein and RNA is 1:1. It contains small amount of metal ions Mg++, Ca++, Mn++ etc. The 70S ribosome contains 3 rRNAs (5S, 16S and 23S) and 52 types of proteins. The 80S ribosome contains 4 rRNAs (5S, 5.8S, 18S and 28S) and 80 types of proteins.

Ribosomes are spherical, ovoid, granular and bulky organelles. It can be triangular or pentagonal. Its diameter is 150-200Å. It is 22nm in width and 20nm in height. Each ribosome has two subunits. The smaller subunit is at the top and the larger subunit is at the bottom. The small subunit consists of three parts. Head, Foot and Stage. The large subunit consists of three parts. Apex, peduncle and swollen center.

In real cells, there is a groove where the two subunits of the ribosome meet. Proteins are synthesized in this cavity. A narrow tunnel runs through the large subunit from the shaft. Endoplasmic reticulum moves through these tunnels. When two subunits of a ribosome are joined, four sites appear. Aaminoacyl site, peptidyl site, exit site and mRNA attachment site. Many ribosomes join together to form polyribosomes. Ribosomes associated with chloroplasts, mitochondria and nuclear membranes are called ribonucleo-protein particles. E. coli bacteria contain 1300-20,000 ribosomes. That is, about 22 percent of the dry weight of E. coli bacteria is ribosomes.

There are two types of ribosomes.

1. 70S ribosomes: 70S ribosomes are present in primitive cells. It is small, with a diameter of 150Å and a molecular weight of 2.7×106 Daltons. Its two sub units are 50S and 30S. During protein synthesis, the 50S and 30S subunits combine to form the 70S unit in progenitor cells. Bacteria, mitochondria and chloroplasts contain 70S ribosomes.
2. 80S ribosomes: 80S ribosomes are present in real cells. Its molecular weight is 40×106 daltons. The two subunits of the 80S ribosome are 60S and 40S. During protein synthesis, the 60S and 40S subunits combine to form the 80S unit in normal cells.

In addition, 77S ribosomes are known to exist in fungi and 55S ribosomes in mammalian mitochondria.

25% of bacterial cells are ribosomes. The number of ribosomes in a cell of E. coli is 10,000. The size of the ribosome in a normal cell is twice that of a protocell. Mammals can have up to 10 million ribosomes per cell.

Ribosomes are produced from DNA in primitive cells. Ribosomes are synthesized during transcription of the operon in the cytoplasm of the primitive cell. In real cells, two subunits are made separately inside the nucleus. Later the two subunits move to the cytoplasm and combine to form ribosomes.

In 1953 scientists Robinson & Brown observed the presence of ribosomes in plant cells. In 1954 Albert Clode discovered it from liver cells and named it microsome. It is also called Claude’s grain. In 1955, the Romanian scientist Palade discovered the ribosome as the heavy substance of the cell. In 1958, Richard B. Robert named microsome as ribosome.

Ribosome is derived from the Greek word ribo meaning ribonucleic acid and soma meaning body. Ribosome means a substance containing nucleic acid. An uncoated protein-synthesizing particle composed of proteins and RNA is called a ribosome. It is called protein factory or protein making machine. Ribosomes in cytoplasm are called cytoribosomes and ribosomes in mitochondria are called mitoribosomes.

The metabolic and metabolic functions of cells are called metabolism. Metabolic functions of cytoplasm are discussed.

1. Photosynthesis: Green plants produce sugary food in the process of photosynthesis. Carbohydrates are the main source of chemical energy for organisms. Carbohydrates are major components of global food security.
2. Conclusion: Glycolysis takes place in the cytoplasm of the cell. Glycolysis is called cytoplasmic secretion. ATP is produced by the oxidation of food substances in the digestion process. ATP provides all the energy in the body.
3. Protein Synthesis: Protein synthesis takes place in the cytoplasm of the cell by the process of translation. Protein plays an important role in the structure and growth of the organism.
4. Reproduction: One of the biological virtues of cytoplasm is the ability to reproduce. It is one of the continuous process of life cycle.
5. Nitrogen Metabolism: Nitrogen is produced from organic matter in the process of nitrification. Again, in the process of denitrification, nitrogen is broken down to produce organic chemicals. The two processes together are called nitrogen metabolism.
6. Metabolism: Different types of proteins, lipids and sugars are metabolized in the cytoplasm.
7. Mineral Salt Metabolism: Cytoplasm metabolizes various types of mineral salts.
8. Source of energy: Carbohydrates present in the cytoplasm are the main source of chemical energy. Lipids provide high levels of energy to the body.
9. Pulse of life: Cytoplasm contains 65-95% water. Another name for water is life. Water is used in all body functions. In its absence, the cell loses its functionality, and the cell may even die.
10. Nucleic acid synthesis: Nucleic acid synthesis in primitive cells takes place in the cytoplasm.

1. Cytoplasm is the main component of cells. It contains all the organelles and the nucleus.
2. It does the biological work of the body.
3. It makes the body grow and develop.
4. It responds to excitement. Demonstrates characteristics of organisms through responses.
5. Aids cell movement through cyclolysis.
6. It contains enzymes.
7. It acts as a source of energy.
8. Maintains the ionic balance of the body.
9. It regulates the acidity and alkalinity of cells.
10. Maintains pressure and fluid density.
11. It controls the heartbeat of the body.
12. It plays an important role in the reproduction of organisms.
13. It causes chemical reactions in cells.
14. It helps in the elimination of waste products produced in the process of excretion.
15. Cytoplasmic matrix increases and causes cell growth.
16. It helps in water absorption.
17. Maintains a suitable environment for biochemical reactions in cells.

1. Protein: Protein content in cytoplasm is 7-10%. It contains three types of proteins.

(i) Simple proteins: Among the simple proteins, albumin, globulin, histone, prolamin and protamine are prominent.

(ii) Complex proteins: The main major complex proteins are glycoproteins, nucleoproteins, lipoproteins, chromoproteins, phosphoproteins etc.

(iii) Produced proteins: Produced proteins are mainly proteose, peptone, lipase, protean, peptide etc.

2. Lipids: Lipid content in cytoplasm is 1-3%. The major lipids in the cytoplasm are glycerides, glycolipids, phospholipids, lipoproteins, cholesterol, etc.
3. Carbohydrate: Carbohydrate content in cytoplasm is 1-1.5%. It contains three types of carbohydrates.

(i) Monosaccharides: The main monosaccharides in the cytoplasm are glucose, fructose, galactose etc.

(ii) Disaccharides: Disaccharides are sucrose, maltose, lactose etc.

(iii) Polysaccharides: Polysaccharides are mainly starch and glycogen.

4. Enzymes: Cytoplasm contains enzymes and co-enzymes.
5. Nucleic Acid: Cytoplasm contains DNA and RNA as nucleic acids.