Question

Which of the following statements is NOT CORRECT with respect to the ribbon diagrams shown? (diagram below)

a) The secondary structure of protein 3 is composed entirley of α-helices

b) Protein 2 contains parallel β-strands

c) Protein 1 contains all three types of secondary structures

d) None of these proteins possessess quaternary structure

Which of the following statements is NOT correct with respect to the ribbon diagrams shown? 愛心 O The secondary structure of protein 3 is composed entirely of a-helices O Protein 2 contains parallel β-strands O Protein 1 contains all three types of secondary structures. O None of these proteins possesses quaternary structure.

Answer 1

A secondary structure of protein is made up of coiling of amino acid chains, formation of beta sheets or strands or ribbons and having thin beta turns which stabilises the structure of proteins.

In the above ribbon diagram,

1. ) Protein 1 contains $\fn_cm \small \alpha$ helix, $\fn_cm \small \beta$ strands and thin $\fn_cm \small \beta$ turns. Thus it contains all the three structure of secondary proteins. thus this statement is true.
2. ) Protein 2 contains parralel $\fn_cm \small \beta$ strands. $\fn_cm \small \beta$ strands are aligned parallel to each other by formation of hydrogen bonds in the primary structure. Thus, this statement is also true.
3. ) Protein 3 has $\fn_cm \small \alpha$ helix as well as thin $\fn_cm \small \beta$ turns. This clearly mentions that the protein does not contain only $\fn_cm \small \alpha$ helix. Thus, this statement is not correct.
4. ) A quaternary structure of protein is composed of different chains of amino acid. In the figure above, none of the protein contains different chain of amino acids. Thus this statement is true.