key term - Polypeptide Chain

Definition

A polypeptide chain is a long, continuous sequence of amino acids linked together by peptide bonds, forming the basic structure of proteins. These chains are synthesized during the process of translation, where ribosomes read messenger RNA (mRNA) sequences to assemble the corresponding amino acids into a specific order. The unique sequence of amino acids in a polypeptide chain ultimately determines the protein's structure and function within a cell.

5 Must Know Facts For Your Next Test

1. Polypeptide chains can vary significantly in length, with some consisting of just a few amino acids while others may have thousands.
2. The sequence of amino acids in a polypeptide chain is determined by the genetic code carried by the mRNA, which is transcribed from DNA.
3. Once formed, polypeptide chains undergo folding and modification to achieve their final functional three-dimensional structures, which are crucial for their biological roles.
4. Proteins can be composed of one or more polypeptide chains that may work together to perform specific functions or provide structural support within cells.
5. The function of a protein is directly influenced by the structure and shape that results from the arrangement of its polypeptide chains.

Review Questions

• How do polypeptide chains contribute to protein diversity and function within cells?
  • Polypeptide chains contribute to protein diversity and function through their unique sequences of amino acids, which determine how the protein folds and interacts with other molecules. Each specific arrangement leads to different shapes and properties, allowing proteins to perform various roles, such as enzymes catalyzing reactions or structural components providing support. Therefore, the variation in polypeptide chain sequences is fundamental to the vast array of functions that proteins can carry out in biological systems.
• Discuss the significance of ribosomes in the synthesis of polypeptide chains and how they ensure accuracy during translation.
  • Ribosomes play a critical role in synthesizing polypeptide chains by facilitating the translation process where mRNA is read and tRNA molecules bring the appropriate amino acids. They ensure accuracy through complementary base pairing between mRNA codons and tRNA anticodons, minimizing errors during protein synthesis. This precision is essential for producing functional proteins that can perform their necessary roles in cellular processes.
• Evaluate the impact of mutations in DNA on the sequence of polypeptide chains and potential consequences for protein functionality.
  • Mutations in DNA can lead to changes in the mRNA sequence during transcription, which in turn affects the sequence of amino acids in a polypeptide chain during translation. These alterations can result in altered protein structures that may be non-functional, have reduced effectiveness, or acquire new functions. Such changes can have significant biological consequences, potentially leading to diseases or contributing to evolutionary adaptations as new traits arise from modified proteins.

Related terms

Amino Acids:

The building blocks of proteins, amino acids are organic compounds that combine to form polypeptides and proteins, each having a unique side chain that determines its properties.

Ribosome:

A complex molecular machine found within all living cells that facilitates the translation of mRNA into polypeptide chains by bringing together mRNA and transfer RNA (tRNA).

Peptide Bond: The covalent bond formed between two amino acids during protein synthesis, resulting in the release of water and linking the amino group of one amino acid to the carboxyl group of another.