Q1: Molecular weight of alanine is 89.09 Da. What will be the molecular weight of a 10-residue peptide composed entirely of alanine?

Ans: Formation of a peptide bond between two amino acids is accompanied by release of a water molecule. Synthesis of a decapeptide (a 10-residue peptide) involves formation of nine peptide bonds i.e. removal of nine water molecules. Therefore, the molecular weight of the peptide will be:

Molecular weight	= {(10 × 89.09) – (9 × 18)} Da
	= (890.9 – 162) Da
	= 728.9 Da

Q2: How does a partial double bond on peptide bond put constraints on proteins' conformations?

Ans: Due to partial double bond character, rotation about the peptide bond is not possible therefore restricting the number of conformations a polypeptide chain can adopt. If there were rotation possible about peptide bond, a protein would be able to sample many more conformations.

Q3: Write down the sequence(s) of RNA molecule(s) that the following DNA molecule can generate (assume entire molecule is transcribed to RNA):

5' – TACGCTGAC –3'

3' – ATGCGACTG-5'

Ans: In biological systems, nucleic acids are synthesized from 5' –3' end. Assuming that both the DNA strands can template the transcription, following RNA molecules will be generated:

From 5' – TACGCTGAC –3' strand: 5'–GUCAGCGUA–3'

From 3' – ATGCGACTG-5' strand: 5'–UACGCUGAC–3'

Q4: Which of the following molecules act as enzymes?

Proteins, Nucleic acids, Carbohydrates, Lipids

Ans: Most enzymes are proteins but RNA molecules also catalyze certain biochemical reactions. Therefore, both proteins and nucleic acids can act as enzymes.