● History of Ribosomes./ pls describe and write so facts

Ribosomes are small dense and granular ribonucleoprotein (i.e., RNA and protein) particles found attached on the outer surfaces of endoplasmic reticulum and nucleus as well as freely scattered in cytoplasm, mitochondrial matrix and chloroplast.

Explanation:

History of Ribosomes:

Ribosomes were first isolated from E. coli by Tissieres and J. D. Watson (1958), who found that ribosomal RNA alone accounts for 22% of the total weight in rapidly growing cells (90% of total RNA). Palade (1953) was the first to observe the ribosomes as dense particles or granules in electron microscope. Upon isolation they were shown to contain approximately equal amounts of RNA and protein.

Size of Ribosomes:

There are mainly two sizes of ribosomes — (i) One is smaller prokaryotic found in bacteria and blue—green algae, having a sedimentation coefficient 70S equivalent to a molecular weight of 2.7 × 106 daltons. (Dalton is the unit of molecular weight. One Dalton is equal to the weight of one hydrogen atom), (ii) Other is of eukaryotic cells of plants and animals of 80S coefficient with a molecular weight of about 4 × 106 daltons.

igneous rocks which formed by the crystallization of magma at the surface of the earth called extrusive rocks. they are characterized by fine-grained textures because the rapid cooling at or near the surface did not provide enough time for large crystals to grow.

he forelimbs below belong to four species that descended in a direct line from the ancestral mammal shown above. of the four descendants shown, which species most likely appeared earliest in evolutionary history?