What is formed when two identical or different amino acid units are joined together?

Select the correct match for $X$ and $Y$:

Column $X$	Column $Y$
$(1)$ Primary protein	$(P)$ Globular or fibrous form
$(2)$ Secondary protein	$(Q)$ Three-dimensional arrangement of a single polypeptide chain
$(3)$ Tertiary protein	$(R)$ Gene-controlled
$(4)$ Quaternary protein	$(S)$ Helical or pleated sheet form

$S$ - Statement: Proteins are called conjugated proteins when they are associated with substances other than amino acids.
$R$ - Reason: Chlorophyll is essential for photosynthesis.

Which of the following groups consists of amino acids with non-polar $R$ groups?

Which of the following is a sulfur-containing amino acid?

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: