Hanisha's+Ribosomes

= **__Ribosomes__ ** =


 * Ribosomes are a necessity to all living organisms
 * They are organelles that make proteins for the cell
 * In fact, the tiny ribosomes are made of 40% protein and the other 60% ribosomal RNA [rRNA]
 * RNA is a genetic term for ribonucleic acid, which is any class of single stranded molecules transcribed from the nucleus, mitochondria, or chloroplasts' DNA, containing along the DNA strand a linear sequence of nucleotide bases that matches it.
 * The composition of the RNA molecule is identical with the DNA except for the substitution of the sugar ribose for deoxyirbose and the substitution of the nucleotide base uracil for thymine
 * Ribosomes are usually referred to as organelles, however, but unlike true organelles, ribosomes are not typically bound to a membrane and they are extremely minute
 * In order to physically view ribosomes, an electron microscope is necessary
 * Some cells have over a million ribosomes, but most simply have a modest few thousand of them
 * Ironically, Ribosomes are mostly bound to the [rough] endoplasmic reticulum and the nuclear envelope, but they are also scattered throughout the cytoplasm
 * The ribosomes attached to the cell membrane are called bound ribosomes, and the ones that float untouched in the cytoplasm are free ribosomes
 * Seeing as the ribosomes sole task is to make proteins for the cell, they flourish in cells that are highly active in protein synthesis, namely brain and pancreatic cells
 * A few of the proteins are for the cell's own internal use, particularly the ones produced by free ribosomes
 * On the contrary, most of the proteins made by bound ribosomes are exported outside of the cell.
 * In eukaryotes the ribosomes' rRNA are categorized into four strands, and in prokaryotes three strands are standard
 * Eukaryote ribosomes are made and arranged in the nucleolus; ribosomal proteins enter as well and unite with the four strands of rRNA to create the two ribosomal subunits, one large and the other small; this procedure is how ribosomes are made in the cell
 * <span style="color: #57c7c7; font-family: Arial,Helvetica,sans-serif;">The ribosomal units leave the nucleus through nuclear pores and join once in the cytoplasm for protein synthesis; when proteins are not being made the ribosome units are separated
 * <span style="color: #c1b0e8; font-family: Arial,Helvetica,sans-serif;">In 200, the complete three dimensional form of a ribosome, its subunits both large and small, was established
 * <span style="color: #c1b0e8; font-family: Arial,Helvetica,sans-serif;">Proof gleaned off of this discovery pointed out that the rRNA, not the proteins, has built in information and functions for the ribosome to follow
 * <span style="color: #c1b0e8; font-family: Arial,Helvetica,sans-serif;">The proteins of a ribosome helped to fill in structural gaps and enhance protein synthesis; even though the process can still go on with out them, it won't go quite as fast
 * <span style="color: #c9c5c5; font-family: Arial,Helvetica,sans-serif;">A ribosome's units are commonly described by their Svedberg[**s**] values which are based upon their rate of sedimentation in a centrifuge
 * <span style="color: #c9c5c5; font-family: Arial,Helvetica,sans-serif;">A eukaryotic cell's ribosomes mainly have Svedberg values of 80S and are composed of 40S and 60S subunits
 * <span style="color: #c9c5c5; font-family: Arial,Helvetica,sans-serif;">Prokaryotic cells have values of 70s and are have ribosomes formed from 30s and 50s subunits
 * <span style="color: #c9c5c5; font-family: Arial,Helvetica,sans-serif;">Svedberg values are not additive, so the values of the subunits do not result in the value for the whole cell
 * <span style="color: #c9c5c5; font-family: Arial,Helvetica,sans-serif;">This is because the rate of sedimentation of a molecule depends on its size and shape rather than its molecular weight
 * <span style="color: #085408; font-family: Arial,Helvetica,sans-serif;">Protein synthesis requires two other kinds of RNA molecules in addition to rRNA
 * <span style="color: #085408; font-family: Arial,Helvetica,sans-serif;">Messenger RNA[mRNA] provides the basic formatting and information from the cellular DNA for building a particular protein
 * <span style="color: #085408; font-family: Arial,Helvetica,sans-serif;">Transfer RNA[tRNA] brings amino acids, protein building blocks to the ribosome
 * <span style="color: #df5d5d; font-family: Arial,Helvetica,sans-serif;">Three close-lying aminoacyl binding sites for a tRNA molecule attached to the next amino acid in the protein
 * <span style="color: #df5d5d; font-family: Arial,Helvetica,sans-serif;"><span style="color: #df5d5d; font-family: Arial,Helvetica,sans-serif;">The peptidyl binding sites for the central tRNA molecule containin g the developing peptide chain, and it also includes an exit binding site for to discharge used tRNA molecules from the ribosome
 * <span style="color: #df5d5d; font-family: Arial,Helvetica,sans-serif;">After the protein backbone amino acids are polymerized, the ribosome releases the protein and it is transported to the cytoplasm in prokaryotes or to the golgi apparatus in prokaryotes
 * <span style="color: #ff009f; font-family: Arial,Helvetica,sans-serif;">There the proteins are completed and released inside or outside the cell



[]

[]

media type="custom" key="11248602" width="80" height="80" media type="custom" key="11248820" width="80" height="80"