Q5. Assertion: the structure of an amino acid changes with the pH of its solution. Reason: the –NH and –COOH groups of amino acids are ionisable. Are both true, and does the reason explain the assertion?
Both are true, and the reason explains the assertion (NCERT page 106).
Q6. Name three aromatic amino acids.
Tyrosine, phenylalanine and tryptophan (NCERT page 106).
Q7. Which nitrogen bases does NCERT list, and what is the nucleotide of uracil called?
Adenine, guanine, cytosine, uracil and thymine; the uracil nucleotide is uridylic acid (NCERT page 106).
Q8. By weight, which element is more abundant in the earth’s crust than in the human body: oxygen or calcium?
Calcium: 3.6 per cent of the crust against 1.5 per cent of the body. Oxygen is the other way round: 46.6 per cent of the crust and 65.0 per cent of the body (NCERT Table 9.1, page 105).