Question

What is the highest level of protein structure in each of the protein examples below? Move each example to the correct classification.

Answer 1

Concepts and reason

Amino acids are the building blocks of proteins. There are a total of 20 amino acids. Proteins are the polymers composed of amino acids chains, known as the polypeptides. The arrangement of the polypeptide chains containing the amino acids in a three dimensional manner is known as the protein structure. The protein structure can be primary, secondary, tertiary or quaternary.

Fundamentals

The primary structure is the first level or simplest level of the protein structure. The primary structure involves the arrangement of the amino acids in a sequence known as the polypeptide chain. The secondary structure has α helices and β sheets with different types of interactions between the amino acids of a polypeptide chain. The tertiary structure has the three dimensional form with extra loops and helices. The quaternary structure is more complex than the tertiary structure and is formed by a multiple complex of subunits.

The primary structure involves the arrangement of amino acids in a sequence. The bond between the amino acids in the primary structure involves the disulfide bonds and peptide bonds, which are covalent in nature. An example of primary structure is the amino acid sequence of myoglobin, insulin polypeptide chains, A and B.

There are different forms of a secondary structure of a protein. Secondary structure of a protein is formed by the repeating forms known as helix and beta sheets. The coiled helical arrangement of a polypeptide chain like spring is known as the helix. The hydrogen bonds hold the folding back of the polypeptide chain that makes it appear side by side to form a beta sheet. Examples of secondary structures involve the helixes and beta sheets.

Proteins have one or more domains. The interactions between the side chains and the polypeptide backbone, which are located with distance between them forms the tertiary structure. Only one polypeptide chain is involved in the formation of tertiary structure. An example of tertiary structure involves the single hemoglobin subunit with heme.

The quaternary structure is formed by the multiple subunits, which includes the union of individual subunits. This includes different interactions such as hydrogen bonding, salt bridges, disulfide bonds, and hydrophobic interaction as present in the tertiary structure. An example of quaternary structure is the hemoglobin.

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