Translation (mRNA to protein) | Biomolecules | MCAT | Khan Academy

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A deep dive into how mRNA is translated into proteins with the help of ribosomes and tRNA.
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Hands down the best possible explanation I have ever heard. You are a blessing to mankind. Thank you.

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This is the most clearly explained video on translation I have watched. Simplifies the complex concept. Thank you Khan Academy and the tutor.

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Sir your teaching is exceptional. I have been struggling to find a good and clear explanation of translation all over youtube but couldn't find one. But guess what. I stumbled upon your beautiful and super simple explanation of the same. Thank you so much.

[@chopotronichappiness8917]

I've always had this problem with these sites in ribosome, like what are they exactly and what are they for?- and now it's clear. Sal you are a blessing ♥

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[@rabeaahsan2070]

During and after translation, polypeptides may need to be modified before they are biologically active. Post-translational modifications include: removal of translated signal sequences-short tails of amino acids that aid in directing a protein to a specific cellular compartment proper “folding” of the polypeptide and association of multiple polypeptide subunits, often facilitated by chaperone proteins, into a distinct three-dimensional structure proteolytic processing of an inactive polypeptide to release an active protein component, and various chemical modifications (e.g., phosphorylation, methylation, or glycosylation) of individual amino acids.

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[@jamessears8289]

i think i missed a detail- does the ribosome float around and kind grab tRNA or are they drawn towards it? or what? how does the ribosome come in contact with tRNA?

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[@kumbiraideon5505]

This is wonderful. Thank you for a simplified version of translation. Sometimes i prefer watching these summarized videos than reading a book..But i got a question in relation to the 'E, P, A' sites how is it possible that we have an Exit on the 5' yet the mRNA is run thru the ribosome from 5' 3' direction ..Can you assist on that maybe i missed it

[@AdaTrimaj]

I think it is a mistake, the 5-3 direction should be opposite in that video to make sense. Evrything else seems to be okay.

[@thepsychhike7177]

its not a mistake. the E site is on 5' bc the ribosome is moving towards 3' but the codons are still at the same place. so the tRNA which is initially on p site shifts to the E site not bc it is moving towards 5' end but bc the ribosome is moving towards 3' end and the tRNA is still in its position.

[@yourfuturedocburenbeiya]

This is so awesome and so clear!! You made this fascinating process come to life and this video wasn’t even animated!! Thank you sir for all you do!!

[@pavellambracht5823]

So, theoretically all proteins start with Methionine?

[@dameind.2246]

Pavel Lambracht Yep. Without AUG, no translation occurs and no protein formed.

[@maheerkhan8500]

Wow. I didn't realize that. *BRAIN FART* :D

[@R-Tex.]

Most of the proteins loose the methionine residue in post-translation processing.

[@josephmoore4764]

In eukaryotic cells and Archea. Prokaryotes use a variant called fMet

[@graciebotsford2674]

That's exactly what I thought about, and I think you are correct.

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[@rebelScience]

Guys, I am still puzzled with one question: So we have Chromosomes -> DNA in a nucleus of the cell. Then, we have Translation phase where we get Proteins, but where do Proteins live? Do they live inside the cell (cytoplasm) ? So each cell creates it's own Proteins or each cell creates different proteins and they leave the cell and work 'outside' the cell? And in this case, what is 'outside' the cell? Any material/video, explaining this are more then welcome!

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Thanks sir I tried to learn Translation but failed… But your video has cleared all my concepts about translation.😊 May God bless you

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Awesome! Thank you

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[@marcoferreira3832]

you can call the A-site as the arrival site

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Than you SO MUCH for making this video!!! This helps a lot!!!

[@maazhaji8904]

Great video, explains tRNA and mRNA interactions so well. My mind can visualize it smoothly now. Also, super interesting fact about the antibiotics at the end!

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So well explained 👌

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legendary biology teacher

[@rabeaahsan2070]

In prokaryotes and eukaryotes, the basics of elongation of translation are the same. In E. coli, the binding of the 50S ribosomal subunit to produce the intact ribosome forms three functionally important ribosomal sites: The A (aminoacyl) site binds incoming charged aminoacyl tRNAs. The P (peptidyl) site binds charged tRNAs carrying amino acids that have formed peptide bonds with the growing polypeptide chain but have not yet dissociated from their corresponding tRNA. The E (exit) site releases dissociated tRNAs so that they can be recharged with free amino acids. There is one notable exception to this assembly line of tRNAs: During initiation complex formation, bacterial fMet−tRNAfMet or eukaryotic Met-tRNAi enters the P site directly without first entering the A site, providing a free A site ready to accept the tRNA corresponding to the first codon after the AUG. Elongation proceeds with single-codon movements of the ribosome each called a translocation event. During each translocation event, the charged tRNAs enter at the A site, then shift to the P site, and then finally to the E site for removal. Ribosomal movements, or steps, are induced by conformational changes that advance the ribosome by three bases in the 3′ direction. Peptide bonds form between the amino group of the amino acid attached to the A-site tRNA and the carboxyl group of the amino acid attached to the P-site tRNA. The formation of each peptide bond is catalyzed by peptidyl transferase, an RNA-based ribozyme that is integrated into the 50S ribosomal subunit. The amino acid bound to the P-site tRNA is also linked to the growing polypeptide chain. As the ribosome steps across the mRNA, the former P-site tRNA enters the E site, detaches from the amino acid, and is expelled. Several of the steps during elongation, including binding of a charged aminoacyl tRNA to the A site and translocation, requires energy derived from GTP hydrolysis, which is catalyzed by specific elongation factors. Amazingly, the E. coli translation apparatus takes only 0.05 seconds to add each amino acid, meaning that a 200 amino-acid protein can be translated in just 10 seconds. The termination of translation occurs when a nonsense codon (UAA, UAG, or UGA) is encountered for which there is no complementary tRNA. On aligning with the A site, these nonsense codons are recognized by release factors in prokaryotes and eukaryotes that result in the P-site amino acid detaching from its tRNA, releasing the newly made polypeptide. The small and large ribosomal subunits dissociate from the mRNA and from each other; they are recruited almost immediately into another translation init iation complex.

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This means the whole polypeptide chain binds to a new tRNA at A site every time and the older tRNA they were attached to gets disposed through E site

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how was it

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