Short note on ribosomes

• Ribosomes were discovered by Robinson and Brown in plant cells and by Palade in animal cells. • Ribosomes are naked ribonucleoprotein protoplasmic particles (RNP) with a length of 200-340 Angstrom and diameter of 170-240 Angstrom which function as the sites for the protein or polypeptide synthesis. • Ribosomes are popularly known as protein factories. They are subspherical in the outline. A covering membrane is absent. Each ribosome consists of two unequal subunits, larger dome-shaped, and smaller oblate-ellipsoid. • The large subunit has a protuberance, a ridge, and a stalk. The smaller subunit possesses a platform, cleft, head, and base. • It is about half the size of the larger subunit.

Ribosomal RNA Definition Ribosomal ribonucleic acid (rRNA) is the RNA component of ribosomes, the molecular machines that catalyze protein synthesis. Ribosomal RNA constitute over sixty percent of the ribosome by weight and are crucial for all its functions – from binding to mRNA and recruiting tRNA to catalyzing the formation of a peptide bond between two amino acids. Even the structure of a ribosome is determined by the three-dimensional shape of its rRNA core. Proteins present in the ribosome serve to stabilize this structure through interactions with the core. Ribosomal RNA are transcribed in the nucleus, at specific structures called nucleoli. These are dense, spherical shapes that form around genetic loci coding for rRNA. Nucleoli are also crucial for the eventual biogenesis of ribosomes, through sequestration of ribosomal proteins. Discovery of Ribosomal RNA Ribosomal RNA was discovered during cell fractionation experiments investigating the role of RNA viruses in causing cancer. Fractionation is a method where cell membranes are carefully and selectively removed while keeping the function of cellular organelles intact. This homogenized cytoplasm is then centrifuged at increasing speeds so that organelles separate according to density. The initial experiments that revealed the presence of rRNA extracted a fraction that was thought to represent a new sub-cellular organelle, microsome, specializing in protein synthesis. Later, it was seen that it was the presence of r...

Facts about Ribosomes What are Ribosomes? Ribosomes are a compact, molecular cellular organelle found inside living cells. This cell organelle is mainly involved in the synthesis of proteins and the process is called protein synthesis or translation. In this process, proteins are produced with the help of amino acids. The synthesis of protein is a fundamental and essential function performed by all living cells. Every single cell requires ribosomes to manufacture proteins, therefore, ribosomes are called specialized cell organelles. Read more about- Ribosomes are the only cell organelles which can synthesize proteins and are widely used in the production of antibiotic drugs. Let’s learn some more interesting facts about ribosomes. There are various interesting and amazing facts about ribosomes. A very few of them are discussed below point-wise. Amazing Facts about Ribosomes Fact- No-1 Ribosomes are very important Fact- No-2 In the ribosome, the word “rib” is derived from ribonucleic acid (RNA) which provides the instructions on making proteins. Fact- No-3 There are two different types of ribosomes including- the 70s, which are found only in the prokaryotic cells and 80s, found only in the eukaryotic cells. Also Read: Fact- No-4 Ribosomes are present in great numbers. More than thousands of ribosomes can be found in a single bacterial cell. Whereas, in complex organisms such as humans, plants and animals, a single cell can have around hundreds of thousands of Ribosomes. I...

Solution (i) Ribosomes These are non-membrane bound organelle which are noticeable with electron microscope only. These were noted by Nobel laureated George Palade in animal cell in 1953. He named them ribosomes in 1955. Ribosomes are found in both prokaryotic as well as eukaryotic cell. They are about 15 nm by 20 nm is size and are made up of two subunits, i.e., 50s and 30s in prokaryotic cell while 60s and 40s in eukaryotic cell. Ribosomes are the site of protein synthesis. (ii) Inclusion bodies In prokaryotic cells reserve material is stored in the cytoplasm in the form of inclusion bodies. These are present freely in cytoplasm. These lack any membrance system around them. For example, phosphate-granules, cyanophycen granules and glycogen granules.