Ribosomes: Structure, Type, Function

Every organism’s basic structural and functional units are cells. They are divided into two categories: prokaryotic and eukaryotic. Prokaryotic cells can be found in species belonging to the bacteria and archaea domains. Eukaryotic cells, on the other hand, are found in fungi, animals and plants. There are some structural and functional distinctions between these two types of cells. The membrane-bound cell organelles, including the endoplasmic reticulum, are not found in the prokaryotic cells. Nonetheless, eukaryotic and prokaryotic cells share several fundamental characteristics, such as:

1. The plasma membrane, also commonly known as the cell membrane, separates the cells. It protects the cells by acting as a selective barrier.
2. Within the cells, there is a jelly-like natural substance, called cytosol, which performs several activities.
3. DNA can be found in the chromosomes of a cell. This section is involved in the expression of traits and heredity.
4. Ribosomes are found in all cells and are responsible for the production of the protein that is essential for cellular functioning.

Ribosomes:

The ribosome’s current understanding is based on the advent of the electron microscope, ultracentrifugation, and radioisotopic method. Because they are engaged in the protein synthesis process, ribosomes are referred to as protein factories. Ribosomes are complex molecules made up of ribosomal RNA molecules and proteins.

Ribosomes are present in every cell in the body. They can be seen both freely, and bound to the surface of the endoplasmic reticulum in eukaryotic cells. The rough endoplasmic reticulum is the name for this type of endoplasmic reticulum. They are located in the mitochondria, nucleolus, and chloroplasts, among other places.

Ribosomes are tiny, averaging just about 25 nanometres in diameter. Free ribosomes are found free in the cytoplasm, while attached ribosomes are coupled to the outside of the endoplasmic reticulum or nuclear envelope to manufacture proteins. Attached ribosomes create proteins that are designed for membrane incorporation, bundling into cellular organelles such as lysosomes, and export.

History: In 1953, George Palade observed ribosomes for the first time using an electron microscope.

Structure of Ribosome:

1. Ribosomes are non-membranous organelles that can be found in both bacterial and eukaryotic cells.
2. Ribosomes are made up of two spherical subunits that are joined together to form a whole unit with a diameter of 200 Aº.
3. The bigger subunit of the ribosome is structured like a dome or icosahedral in electron microscopy, while the smaller subunit is shaped like a cape on the level surface of the larger subunit.
4. Numerous kinds of ribosomal ribonucleic acids (rRNAs) and countless proteins make up both subunits.
5. The sediment coefficient of the bacterial ribosome is the 70S, and it is composed of a 50S bigger subunit and a 30S smaller subunit.
6. The ribosome of a eukaryotic cell has an 80S sediment coefficient, which is made up of a 50S bigger subunit and a 40S smaller subunit.

Types of Ribosome:

1. Ribosomes have size, structures and compositions similar. However, they have been divided into two groups based on the sedimentation coefficient:
   1. 70S ribosomes: They are smaller than 80S ribosomes and can be found in bacterial cells, chloroplasts and mitochondria.
   2. 80S ribosomes: The 80S ribosome is found in eukaryotic cells.

The Function of Ribosomes: 

1. Ribosomes are the sites wherein proteins are synthesized.
2. Ribosomes in the cells undergo the process of combining amino acids to produce proteins. These proteins are involved in a variety of biological processes.
3. t-RNA is formed when mRNA is contained by the ribosomal unit during protein synthesis.
4. They take part in DNA transcription, which converts DNA into mRNA.The free ribosomes participate in the synthesis of protein in the cytoplasm. It is used by the cytoplasm. However, the protein synthesis, which takes place by the ribosomes found attached to the rough ribosome, is transported outside the cell.
5. In the cytoplasm, free ribosomes are involved in protein synthesis. The cytoplasm makes use of it. Protein synthesis, which is carried out by ribosomes linked to the rough ribosome, is carried out outside the cell.