Which of the following element is not usually present in all proteins?
Correct answer: D. Sulphur
- A. Carbon
- B. Hydrogen
- C. Nitrogen
- D. Sulphur
Explanation
All proteins contain carbon, hydrogen, and nitrogen. Carbon forms the backbone of amino acids, while hydrogen is found in amino and carboxyl groups. Nitrogen is essential for peptide bond formation and is present in the amino groups of amino acids. However, sulfur is not universally present in all proteins; it is found only in certain amino acids like cysteine and methionine. Therefore, sulfur is the element that is not usually present in all proteins.
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About Macromolecules
Proteins are classified by shape, composition and structure, from primary amino acid sequence to secondary, tertiary and quaternary organisation, and their biological roles are linked to this structure. Enzymes are examined as protein biocatalysts, including active sites, substrate specificity, activation energy, cofactors and factors affecting activity.
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