Which of the following element is not usually present in all proteins?
Correct answer: D. Sulfur
- A. Carbon
- B. Hydrogen
- C. Nitrogen
- D. Sulfur
Explanation
Proteins are macromolecules composed of amino acids, which are linked together by peptide bonds. While carbon, hydrogen, nitrogen, and oxygen are consistently found in all proteins, sulfur is not universally present in all proteins. The presence of sulfur in proteins is dependent on the specific amino acid composition.
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About Classification of Proteins
Proteins are classified by composition as simple, conjugated and derived proteins, and by shape as fibrous or globular proteins. The topic relates these classes to examples such as albumin, keratin, collagen, haemoglobin and casein, while distinguishing structural proteins from proteins with transport, catalytic or regulatory roles.
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