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

Summary

This video explains the process of translation, where genetic information encoded in messenger RNA (mRNA) is used to synthesize proteins. It covers key concepts like the role of ribosomes, transfer RNA (tRNA), and the codon system that ensures the correct amino acids are added in the right sequence. The video illustrates how the ribosome reads the mRNA, starting at the start codon (AUG), and proceeds along the mRNA to form a polypeptide chain. Additionally, it touches on antibiotic mechanisms, highlighting how certain antibiotics can target bacterial translation without affecting human cells.

Takeaways

• 😀 DNA is made up of long strands of genes that encode the information for protein synthesis.
• 😀 The central dogma of biology describes the process of converting genetic information from DNA to RNA, and then from RNA to proteins.
• 😀 Transcription is the process where a gene in DNA is copied into messenger RNA (mRNA). In eukaryotes, this results in pre-mRNA, which is processed before becoming mature mRNA.
• 😀 The ribosome plays a key role in translation, where it reads mRNA and synthesizes a polypeptide chain using amino acids.
• 😀 Codons, groups of three nucleotides on mRNA, correspond to specific amino acids. The start codon (AUG) signals the beginning of translation.
• 😀 There are 64 possible codons, but only 22 standard amino acids are used to make proteins, making the genetic code highly efficient.
• 😀 Transfer RNA (tRNA) molecules carry specific amino acids and have anticodons that match the codons on the mRNA.
• 😀 The ribosome has three sites: A-site (where tRNA enters with amino acids), P-site (where the polypeptide chain is formed), and E-site (where tRNA exits).
• 😀 As the ribosome moves along the mRNA, it facilitates the formation of peptide bonds between amino acids, elongating the polypeptide chain.
• 😀 The process continues until a stop codon is encountered, signaling the termination of translation and release of the completed protein.
• 😀 Antibiotics can target bacterial ribosomes to disrupt their protein synthesis, without affecting eukaryotic ribosomes, helping to treat bacterial infections.

Q & A

What is the central dogma of biology?

The central dogma of biology refers to the process of going from the gene, encoded in DNA, to messenger RNA (mRNA) through transcription, and then translating that mRNA into a protein, which is composed of polypeptides made up of amino acids.

What is the role of ribosomes in translation?

Ribosomes play a crucial role in translating the messenger RNA (mRNA) into a polypeptide sequence. They travel along the mRNA, reading the codons and assembling the corresponding amino acids into a protein.

What is the difference between pre-mRNA and mRNA in eukaryotic cells?

In eukaryotic cells, the initial transcript from DNA is called pre-mRNA, which undergoes processing, including the removal of introns and the addition of a cap and tail. After this processing, it becomes mRNA, which can then be used in translation.

What is a codon, and how does it relate to amino acids?

A codon is a sequence of three nucleotides in mRNA that codes for a specific amino acid. Each codon corresponds to one of the 22 standard amino acids, and the sequence of codons determines the amino acid sequence in the resulting protein.

Why is the AUG codon important?

The AUG codon is the start codon, signaling the beginning of translation. It codes for the amino acid methionine, which is typically the first amino acid in a newly synthesized polypeptide chain.

What are stop codons and how do they function in translation?

Stop codons (UAA, UAG, and UGA) are specific sequences of three nucleotides that signal the end of the translation process. They instruct the ribosome to release the newly formed polypeptide chain.

What is tRNA, and how does it assist in protein synthesis?

tRNA (transfer RNA) is a type of RNA that helps in protein synthesis by carrying specific amino acids to the ribosome. Each tRNA molecule has an anticodon that pairs with the corresponding codon in mRNA, ensuring the correct amino acid is added to the growing polypeptide chain.

What are the roles of the A-site, P-site, and E-site in the ribosome?

The A-site (Aminoacyl site) is where tRNA with an amino acid binds to the ribosome. The P-site (Peptidyl site) holds the growing polypeptide chain, while the E-site (Exit site) is where the tRNA, after donating its amino acid, exits the ribosome.

How do antibiotics affect the translation process in bacteria?

Antibiotics can target the ribosomes of prokaryotes, which are structurally different from eukaryotic ribosomes. By disrupting the translation process in bacterial ribosomes, antibiotics can stop bacterial protein synthesis without harming human cells.

How does the ribosome ensure that the correct amino acids are added during translation?

The ribosome ensures the correct amino acids are added by matching the anticodon on the tRNA with the corresponding codon on the mRNA. This precise pairing ensures the correct amino acid is added to the growing polypeptide chain.