When catabolism of proteins exceeds synthesis of proteins,then:

Which of the following pairs represents amino acids with polar and uncharged '$R$' groups?

Which of the two groups of the following formula is involved in peptide bond formation between different amino acids?

Which of the following pairs of amino acids contains non-polar '$R$' groups?

The amino acid with a polar and uncharged '$R$' group is .......... .

The triple helical structure of collagen was published in Nature in $1954$, and the analysis of the allowed conformations of proteins was performed through the use of the: