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Ribosome

Definition

noun, plural: ribosomes

(Science: cell biology)

(1) A minute particle composed of protein and ribonucleic acid (RNA) that serves as the site of protein synthesis.

(2) A molecule consisting of two subunits that fit together and work as one to build proteins according to the genetic sequence held within the messenger RNA (mRNA). Using the mRNA as a template, the ribosome traverses each codon, pairing it with the appropriate amino acid. This is done through interacting with transfer RNA (tRNA) containing a complementary anticodon on one end and the appropriate amino acid on the other.

(3) A sphere-shaped structure found in the cytoplasm of prokaryotic and eukaryotic cells. Some ribosomes occur freely in the cytosol whereas others are attached to the nuclear membrane or to the endoplasmic reticulum (ER) giving the latter a rough appearance, hence, the name rough ER or rER.


Supplement

Ribosomes of prokaryotes (e.g. bacteria) are smaller than most of the ribosomes of eukaryotes (e.g. plants and animals). However, the plastids and mitochondria in eukaryotes have smaller ribosomes similar to those in prokaryotes – a possible indication of the evolutionary origin of these organelles.

In mid-1950s, ribosomes were first observed as dense particles or granules by George Palade with his electron microscope. In 1958, the term ribosome was proposed by the scientist, Richard B. Roberts.


Word origin: from ribonucleic acid and Greek: soma, meaning body.

Related forms: ribosomal (adjective).
Related terms: ribosome binding site, ribosome-lamella complex.


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Results from our forum


What kind of cell is it? DUMB QUESTION

... and translation usually occurs in the cytoplasm. Bacterial cells, which have no nucleus and can transcribe and translate as fast as the little ribosome complexes can attach to nascent mRNA.

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by kolean
Sat Aug 22, 2009 7:39 pm
 
Forum: Cell Biology
Topic: What kind of cell is it? DUMB QUESTION
Replies: 1
Views: 55

Two questions about operon (transcription/translation)

... is good, unfortunately biology is not that theoretical. What you described indeed does happen: some policistronic prokaryotic mRNAs have a ribosome binding site (RBS) for each open reading frame. However, others do not: sometimes the last codon of one open reading frame coincides with the ...

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by MrMistery
Sun Aug 02, 2009 11:27 pm
 
Forum: General Discussion
Topic: Two questions about operon (transcription/translation)
Replies: 2
Views: 106

Re: Signaling between the ribosome and synthetase

As far as I know there is no signaling between ribosome and synthetase. tRNAs linked to amino acids are present in the cytosol. The ribosome uses them, stripping off the amino acids. When an aminoacyl-tRNA synthetase encounters an unloaded tRNA, ...

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by jonmoulton
Tue Jun 23, 2009 11:02 pm
 
Forum: Genetics
Topic: Signaling between the ribosome and synthetase
Replies: 3
Views: 209

Signaling between the ribosome and synthetase

In the translation sequence, there is a point at which the ribosome requires a particular amino acid. Is there a signaling process between the ribosome and Aminoacyl tRNA synthetase indicating a particular need? Or are all varieties of aminoacyl-tRNA ...

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by moadeeb
Mon Jun 22, 2009 1:30 pm
 
Forum: Genetics
Topic: Signaling between the ribosome and synthetase
Replies: 3
Views: 209

Re: Any SOLID arguments against evolution?

... many amino acids are in the enzymes which transcribe the mRNA? 2. The RNA journey --Then the mRNA leaves the nucleus like a snake and meets with a ribosome. How many amino acids are in the ribosome? 3. Translation -- Then the mRNA and ribosome lock together like material going through a sewing ...

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by AFJ
Wed Jun 03, 2009 12:15 am
 
Forum: Evolution
Topic: Any SOLID arguments against evolution?
Replies: 106
Views: 16654
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