MPSC Notes - Protein Structure Parts - II

Protein Structure Parts - II

11. How can the binding of two amino acids for the peptide formation be described?

A peptide is formed when a carbon from the carboxyl group of one amino acid is connected to the nitrogen of the amine group of another amino acid. During that binding the hydroxyl of the carboxyl and one hydrogen of the amine is lost resulting in the liberation of one water molecule.

12. What is the binding between two amino acids called?

The chemical bond between two amino acids is called a peptide bond.

13. Do the –R groups bound to the central carbons participate in the union between amino acids?

The peptide bond attaches the nitrogen of the amine group of one amino acid to the carbon of the carboxyl group of another amino acid liberating one molecule of water. So the –R groups do not participate in that bond.

14. Do the –H groups bound to the central carbons participate in the peptide bond?

The central carbons themselves, the –R groups and the hydrogens attached to the central carbons do not participate in the peptide bond.

15. Do the amine and the carboxyl groups attached to central carbons participate in the union between amino acids?

Yes. The nitrogen of the amine group of one amino acid binds to the carbon of the carboxyl group of the other amino acid. The water molecule liberated from the formation of the peptide bond thus has a hydrogen from the amine and an oxygen and another hydrogen from the carboxyl.

16. Does the chemical reaction to unite amino acids incorporate or liberate atoms? What are the chemical entities incorporated or liberated in this reaction?

The union of amino acids by peptide bond liberates atoms. They are liberated as constituents of one molecule of water.

17. Are there different proteins made by the same total number of amino acids?

Different proteins with the same total number of amino acids may exist. In such cases the differentiation is given by the types of amino acids or by the sequence in which they form the protein.

18. Are proteins with the same number of each different amino acid that form them necessarily identical proteins?

Even if many proteins have the same number of each different amino acid that form them, for example, 50 alanines, 70 glycines and 20 histidines, the sequences in which these amino acids are connected may be very different. So if two or more proteins are in such condition of numeric similarity for each type of their constituent amino acids, they are not necessarily identical.

19. What is the essential condition for a protein to be identical to another protein?

For a protein to be identical to another protein it is necessary for the sequence of amino acids that form them to be identical.

20. What is the primary structure of a protein? What is the importance of the primary structure?

The primary protein structure is the linear sequence of amino acids that form the molecule.

The primary structure is the basis of the protein identity. Modification of only one amino acid of the primary structure creates a different protein. This different protein can be inactive or can even have other biological functions.

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