Polypeptide

Definition

A polypeptide is a chain of amino acids linked together by peptide bonds, forming the building blocks of proteins. The sequence and number of amino acids in a polypeptide are determined by the genetic code, which is transcribed into messenger RNA (mRNA) and translated by transfer RNA (tRNA) during protein synthesis. This process highlights the critical relationship between polypeptides, genetic information, and cellular function.

5 Must Know Facts For Your Next Test

1. Polypeptides can consist of a few dozen to thousands of amino acids, determining their unique structure and function.
2. The sequence of amino acids in a polypeptide is critical for its final three-dimensional shape, which ultimately dictates its biological activity.
3. Polypeptides fold into specific shapes through various interactions such as hydrogen bonding, hydrophobic interactions, and disulfide bridges.
4. Different polypeptides can combine to form larger protein complexes, expanding their functional diversity within the cell.
5. The genetic code is organized into codons, where each set of three nucleotides corresponds to a specific amino acid that gets added to the growing polypeptide chain.

Review Questions

• How does the genetic code influence the sequence of a polypeptide during protein synthesis?
  • The genetic code is made up of sets of three nucleotides known as codons, each specifying a particular amino acid. During protein synthesis, messenger RNA (mRNA) is transcribed from DNA and carries the codon sequence to ribosomes. Transfer RNA (tRNA) then interprets these codons by matching them with the corresponding amino acids, adding them one by one to the growing polypeptide chain according to the specified order dictated by the mRNA.
• What role do peptide bonds play in the formation of polypeptides, and how do they impact protein structure?
  • Peptide bonds are essential for linking amino acids together in a polypeptide chain. Formed through a dehydration reaction between the carboxyl group of one amino acid and the amino group of another, these bonds create a stable backbone for polypeptides. The nature of these bonds influences how the polypeptide folds into its secondary and tertiary structures, ultimately determining its function as a protein.
• Evaluate how mutations in the genetic code can affect polypeptide synthesis and lead to changes in protein function.
  • Mutations in the genetic code can lead to changes in the sequence of codons transcribed into mRNA. If a mutation alters a single nucleotide, it may result in a different amino acid being incorporated into a polypeptide or even create a stop codon that prematurely halts translation. These changes can drastically affect the folding and function of proteins, leading to potential malfunctions or diseases. Understanding these mutations is crucial for exploring genetic disorders and developing targeted therapies.

Related terms

Amino Acid: The organic compounds that serve as the building blocks of polypeptides and proteins, each containing an amino group, a carboxyl group, and a unique side chain.

Peptide Bond: The covalent bond formed between two amino acids when the carboxyl group of one reacts with the amino group of another, releasing a molecule of water.

Translation: The process by which ribosomes synthesize polypeptides based on the sequence of codons in mRNA, using tRNA to bring the appropriate amino acids.