Reviewed by MedQGo Editorial Team | Last updated: July 30, 2026
Which of the following amino acids does not participate in protein composition?
Ahomocysteine
Bcystine
Ccysteine
Dthreonine
Correct answer: A. homocysteine
Homocysteine is a sulfur-containing compound that can be converted to cysteine but does not directly participate in protein composition. Cystine, cysteine, and threonine are all involved in the formation of proteins.
Free PDF sample
Get NEET Biology MCQs as a chapter-wise PDF.
Join early access for a free MCQ sample with answers and NCERT-aligned explanations.