Difference between revisions of "Ribosomes"

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[[Ribosomes]] are responsible for assembling the [[proteins]] of the [[cell]]. Ribosomal [[subunits]] are synthesized by the [[nucleolus]]. Depending on the [[protein]] [[production]] level of a [[particular]] [[cell]], [[ribosomes]] may [[number]] in the millions. They are tiny [[round]] [[particles]].
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ribosomes  
 
[[ribosomes]] are typically composed of two subunits: a [[large]] [[subunit]] and a [[small]] [[subunit]]. These two [[units]] [[join]] together when the [[ribosome]] [[attaches]] to [[messenger rna]] to [[produce]] a [[protein]] in the [[cytoplasm]] (cyto-).
 
 
there are two [[places]] that [[ribosomes]] usually [[exist]] in the cell: suspended in the [[cytosol]] and [[bound]] to the [[endoplasmic reticulum]]. These [[ribosomes]] are called [[free]] [[ribosomes]] and [[bound]] [[ribosomes]] respectively. In both [[cases]], the [[ribosomes]] usually [[form]] [[aggregates]] called polysomes (poly-) (also known as polyribosomes).
 
 
[[free]] [[ribosomes]] usually [[make]] [[proteins]] that will [[function]] in the [[cytosol]] while [[bound]] [[ribosomes]] usually [[make]] [[proteins]] that are exported or [[included]] in the [[cells]] [[membranes]]. Interestingly enough, [[free]] [[ribosomes]] and [[bound]] [[ribosomes]] are interchangeable and the [[cell]] can [[change]] their [[numbers]] according to [[metabolic]] [[needs]].
 
  
[[ribosomes]] - [[protein]] CONSTRUCTION TEAMS
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''noun, plural of [[ribosome]]''
[[cells]] [[need]] to [[make]] [[proteins]]. Those [[proteins]] might be used as [[enzymes]] or as [[support]] for other [[cell]] [[functions]]. When you [[need]] to [[make]] [[proteins]], you [[look]] for [[ribosomes]]. [[Ribosomes]] are the [[protein]] builders or the [[protein]] synthesizers of the [[cell]]. They are like construction guys who take one [[amino acid]] at a [[time]] and [[build]] [[long]] [[protein]] [[chains]].
 
  
[[ribosomes]] could be in many [[places]] around the [[cell]]. You might find them [[floating]] in the [[cytoplasm]]. Those [[floating]] [[ribosomes]] [[make]] [[proteins]] that will be used [[inside]] of the [[cell]]. Other [[ribosomes]] are found on the [[endoplasmic reticulum]]. [[Endoplasmic reticulum]] with [[ribosomes]] attached is called [[rough]]. It [[looks]] bumpy under a [[microscope]]. Those attached [[ribosomes]] [[make]] [[proteins]] that will be used [[inside]] the [[cell]] and [[proteins]] made for [[export]] ([[outside]] the [[cell]]).  
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Small round particles in a [[cell]] made up of [[RNA]] and [[protein]] that are primarily involved in the assembly of proteins by translating [[messenger RNA]] (a process called [[translation]]).
  
A [[ribosome]] is not [[just]] one [[piece]]. There are two [[pieces]] or [[subunits]]. Scientists named them 60-S and 30-S. When the [[cell]] [[needs]] to [[make]] [[protein]], [[mrna]] is created in the [[nucleus]]. The [[mrna]] is then sent into the [[cell]] to the [[ribosomes]]. When it is [[time]] to [[make]] the [[protein]], the two [[subunits]] come together and combine with the [[mrna]]. The two [[pieces]] [[lock]] onto the [[mrna]] and [[start]] the [[protein synthesis]].  
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Ribosomes, being entirely [[particulate]], are not considered [[organelles]] when the term organelle is strictly used to refer to [[membraned]] structures. Although in some literature they are referred to as "non-membranous organelles".
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Ribosomes are typically composed of two [[subunits]]: the large and small [[subunits]]. They join as one during [[translation]]; together, they [[catalyze]] the [[translation]] of [[mRNA]] into a [[polypeptide chain]] during [[protein synthesis]], and since their [[active site]]s are made of [[RNA]], ribosomes are also referred to as "[[ribozymes]]."
  
The [[process]] of making [[proteins]] is quite [[simple]]. We [[just]] explained that [[mrna]] is made in the [[nucleus]] and sent into the [[cell]]. The [[mrna]] combines with the [[ribosome]] [[subunits]]. Another [[nucleic acid]] [[lives]] in the [[cell]] - [[trna]], which [[stands]] for [[transfer rna]], and it is bonded to [[amino acids]]. With the [[mrna]] offering [[instructions]], the [[ribosome]] connects to a [[trna]] and [[pulls]] off the [[amino acids]]. Slowly the [[ribosome]] [[makes]] a [[long]] [[amino acid]] [[chain]] that becomes a [[protein]].
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Ribosomes are formed in the [[cytoplasm]] of [[prokaryotic cell]]s. In [[eukaryotic cell]]s, they are formed most often in the [[nucleolus]]. Another difference between ribosomes of [[prokaryotes]] and [[eukaryotes]] is the structure of the ribosomes. [[Prokaryotes]] have [[70S ribosome]]s, each consisting of a small (30S) and a large (50S) [[subunit]]. Eukaryotes have [[80S ribosome]]s, each consisting of a small (40S) and large (60S) [[subunit]]. However, the [[organelles]] like [[chloroplasts]] and [[mitochondria]] that are present only in [[eukaryotic cell]]s also consist of [[70S ribosome]]s resembling those in [[prokaryotes]] (e.g. [[bacteria]]), indicating that these [[eukaryotic]] [[organelles]] have descended from their ancestral [[bacteria]] (see [[Endosymbiotic theory]]).
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In [[eukaryotes]], the ribosomes may be classified as either ‘free’ or ‘bound’. [[Free ribosome]]s may be found suspended in the [[cytosol]] whereas [[bound ribosome]]s are attached to [[endoplasmic reticulum]] (as such called [[rough endoplasmic reticulum]]). Free ribosomes are involved in the [[synthesis]] of [[proteins]] that will function in the [[cytosol]] while bound ribosomes in the [[synthesis]] of [[proteins]] that are to be exported or used within the [[cell membrane]]. The two types of ribosomes have similar function and structure, and in fact, are interchangeable.
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Word origin: from ribonucleic acid and Greek: ''soma'' (meaning body)

Revision as of 11:44, 10 June 2008

ribosomes

noun, plural of ribosome

Small round particles in a cell made up of RNA and protein that are primarily involved in the assembly of proteins by translating messenger RNA (a process called translation).

Ribosomes, being entirely particulate, are not considered organelles when the term organelle is strictly used to refer to membraned structures. Although in some literature they are referred to as "non-membranous organelles". Ribosomes are typically composed of two subunits: the large and small subunits. They join as one during translation; together, they catalyze the translation of mRNA into a polypeptide chain during protein synthesis, and since their active sites are made of RNA, ribosomes are also referred to as "ribozymes."

Ribosomes are formed in the cytoplasm of prokaryotic cells. In eukaryotic cells, they are formed most often in the nucleolus. Another difference between ribosomes of prokaryotes and eukaryotes is the structure of the ribosomes. Prokaryotes have 70S ribosomes, each consisting of a small (30S) and a large (50S) subunit. Eukaryotes have 80S ribosomes, each consisting of a small (40S) and large (60S) subunit. However, the organelles like chloroplasts and mitochondria that are present only in eukaryotic cells also consist of 70S ribosomes resembling those in prokaryotes (e.g. bacteria), indicating that these eukaryotic organelles have descended from their ancestral bacteria (see Endosymbiotic theory).

In eukaryotes, the ribosomes may be classified as either ‘free’ or ‘bound’. Free ribosomes may be found suspended in the cytosol whereas bound ribosomes are attached to endoplasmic reticulum (as such called rough endoplasmic reticulum). Free ribosomes are involved in the synthesis of proteins that will function in the cytosol while bound ribosomes in the synthesis of proteins that are to be exported or used within the cell membrane. The two types of ribosomes have similar function and structure, and in fact, are interchangeable.

Word origin: from ribonucleic acid and Greek: soma (meaning body)