Question

Give an mRNA sequence that will code for the synthesis of metenkephalin. Tyr-Gly-Gly-Phe-Met

Short answer

The mRNA sequence for metenkephalin is UAU GGU GGU UUU AUG.

Step-by-step solution

Understand the Protein Sequence

Metenkephalin is a peptide composed of five amino acids: Tyrosine (Tyr), Glycine (Gly), Glycine (Gly), Phenylalanine (Phe), and Methionine (Met).

Write Amino Acid Code Table

Determine the codon (mRNA) table for each amino acid: - Tyrosine (Tyr) is coded by UAU or UAC. - Glycine (Gly) is coded by GGU, GGC, GGA, or GGG. - Phenylalanine (Phe) is coded by UUU or UUC. - Methionine (Met) is coded by AUG.

Assign Codons to Each Amino Acid

Select one codon for each amino acid based on the known coding sequences: - Tyrosine (Tyr): UAU - Glycine (Gly): GGU - Glycine (Gly): GGU - Phenylalanine (Phe): UUU - Methionine (Met): AUG

Write the mRNA Sequence

Combine the selected codons to construct the mRNA sequence: - UAU GGU GGU UUU AUG

Key concepts

Metenkephalin

Metenkephalin is a small peptide that functions as an endogenous opioid. It is composed of a specific sequence of five amino acids: Tyrosine (Tyr), Glycine (Gly), Glycine (Gly), Phenylalanine (Phe), and Methionine (Met). This sequence is critical for meeting specific biological functions in the body, such as modulating pain and emotional responses.

Endogenous opioids like metenkephalin bind to opioid receptors in the brain, providing analgesic effects and influencing mood. The precise sequence and structure of this peptide allow it to interact efficiently with these receptors. Understanding metenkephalin gives us insight into how peptides and proteins are vital for various physiological processes. Recognizing the role of amino acid sequences in forming such biologically active peptides highlights the importance of protein synthesis in living organisms' functional mechanisms.

Codon Assignment

Codon assignment is a crucial step in translating the genetic code into proteins. Each amino acid in a peptide is coded by triplet sequences of nucleotides called codons. In mRNA, these codons are read during protein synthesis to form the specific sequence of amino acids required.

Assigning the correct codons is critical:

• Tyrosine (Tyr) is coded by the codons UAU or UAC
• Glycine (Gly) can be encoded by GGU, GGC, GGA, or GGG
• Phenylalanine (Phe) is represented by UUU or UUC
• Methionine (Met) is uniquely coded by AUG

Choosing one codon from each option for synthesizing a specific protein is essential. This selection is based on genetic encoding boundaries, optimizing the mRNA's efficiency in facilitating protein synthesis. Codon assignment directly impacts the functionality of the resultant peptide or protein, making accuracy indispensable in genetic translation.

Amino Acids

Amino acids are organic compounds that serve as the building blocks of proteins. They consist of an amino group, a carboxyl group, a hydrogen atom, and a distinctive side chain (R-group) attached to a central carbon atom.

In the context of protein synthesis, amino acids link together via peptide bonds to form polypeptides, which subsequently fold into functional proteins. For metenkephalin, the sequence involves:

• Tyrosine (Tyr) - with a polar side chain contributing to hydrogen bonding
• Glycine (Gly) - the smallest amino acid with a single hydrogen as the side chain, allowing flexibility
• Phenylalanine (Phe) - possessing a large, aromatic side chain, impacting protein structure
• Methionine (Met) - featuring a sulfur-containing side chain, often involved in initiating protein synthesis

The unique properties of each amino acid affect the peptide's characteristics and activity, emphasizing amino acids' relevance in enzymatic reactions and cellular functions.

Protein Synthesis

Protein synthesis is the biological process of building proteins based on the genetic information encoded in DNA. This information is transcribed into mRNA, which travels from the nucleus to the ribosomes in the cytoplasm for translation.

The synthesis proceeds through two main stages:

• Transcription: DNA sequences are transcribed into mRNA.
• Translation: mRNA is decoded by ribosomes to arrange amino acids into a specific polypeptide chain.

During translation, tRNA molecules bring amino acids to the ribosome, matching their anti-codons to the mRNA codons. For metenkephalin, the sequence UAU GGU GGU UUU AUG directs the ribosome to construct the peptide with the appropriate amino acids in the correct sequence.

This process ensures that proteins are synthesized accurately and efficiently, facilitating cell structure, function, and regulation. The synthesis of proteins like metenkephalin showcases the complex yet remarkably organized nature of cellular machinery responsible for life.