Question

PART A

Complete the following vocabulary exercise relating to the level of structure in proteins.

Match the words in the left-hand column with the appropriate blank in the sentences in the right-hand column. 

Part B

Sort the images according to the level of structure in the proteins shown.

Sort the items into the appropriate bin.

Answer 1

Concepts and reason

Amino acids are the building blocks of proteins. There are a total of 20 amino acids. Proteins are polymers composed of amino acid chains, known as polypeptides. The polypeptide chains' arrangement 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.

 

Part A

1.

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 covalent in nature.

2.

There are different forms of a secondary structure of a protein. The 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.

3.

The quaternary structure is formed by 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.

Fibrous and globular proteins are two types of proteins with quaternary structures. These are biologically active. One example of the quaternary structure of a protein is hemoglobin.

4.

The interactions between the side chains and the polypeptide backbone, located with the distance between them, form the tertiary structure. Only one polypeptide chain is involved in the formation of tertiary structure.

Proteins have one or more domains. The side chain present on the amino acids involves the interactions and type of interaction based on the type of side chain of these amino acids.

Part B

The primary structure involves forming the peptide bonds between the amino acids to form a polypeptide chain, which is the simplest form of the protein structure. The secondary structure includes the helix and sheet-like structures formed due to the bonding with the polypeptide backbone. The tertiary structure is the three-dimensional structure formed by a single polypeptide chain. The quaternary structure is a more complex three-dimensional structure with multiple subunits.

The complexity and the presence of different types of bonds and interactions between the amino acids in a polypeptide chain determine a protein's structure.