Asked in PMC Practice Test 26 (2021) 2021Moderate

How many amino acids are constituents of proteins only?

Correct answer: A. 25

  • A. 25
  • B. 20
  • C. 19
  • D. 15

Explanation

"About 170 types of amino acids have been found to occur in cells and tissues. Of these, about 25 are constituents of proteins. Most of the proteins are however, made of 20 types of amino acids."(PTB)

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About Proteins

Proteins are polymers of amino acids joined by peptide bonds, and their function depends on primary, secondary, tertiary and quaternary structure. The topic covers fibrous and globular proteins, enzymes, antibodies, hormones and transport proteins, as well as denaturation by heat or extreme pH.

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