Which of the following statements is true?

• A. Life predominantly uses D-amino acids to build proteins.
• B. Except for Ser, life predominantly uses S-amino acids to build proteins.
• C. All L-amino acids have an S configuration.
• D. Life almost exclusively uses L-amino acids to build proteins.

Answer: (D)

Verified step by step guidance

1. Understand the concept of chirality in amino acids: Amino acids, except glycine, have a chiral center at the alpha carbon, which means they can exist in two enantiomeric forms, L and D.
2. Recognize the biological preference: In biological systems, proteins are almost exclusively composed of L-amino acids. This is a fundamental aspect of biochemistry.
3. Clarify the configuration: The L and D nomenclature is based on the molecule's similarity to the structure of L-glyceraldehyde. It is important to note that L-amino acids do not necessarily have an S configuration; the configuration depends on the specific side chain.
4. Evaluate the given statements: Analyze each statement based on the above concepts. The statement 'Life predominantly uses D-amino acids to build proteins' is incorrect as proteins are made from L-amino acids.
5. Identify the correct statement: The statement 'Life almost exclusively uses L-amino acids to build proteins' is true, aligning with the biological preference for L-amino acids in protein synthesis.