[Campbell Biology P.126] According to Figure 5.14, which of the following statements about a... | Practice Question

According to Figure 5.14, which of the following statements about amino acid classification is correct?

  • A: Tyrosine is classified under nonpolar, hydrophobic side chains due to its aromatic ring.
  • B: Aspartic acid and Glutamic acid are acidic amino acids because their side chains are positively charged.
  • C: Cysteine, despite having a sulfhydryl group, is explicitly noted as sometimes being classified as a nonpolar amino acid due to its weak polarity.
  • D: Histidine is a basic amino acid, but its side chain is negatively charged at pH 7.2.

Explanation

The figure explicitly notes that 'Since cysteine is only weakly polar, it is sometimes classified as a nonpolar amino acid.' Tyrosine is polar due to its hydroxyl group. Aspartic acid and Glutamic acid are acidic because they are negatively charged at physiological pH. Histidine is a basic amino acid and is positively charged at physiological pH.