Biochemistry

To answer this question, we need to understand the structure of amino acids and what characterizes an acidic amino acid. Amino acids are the building blocks of proteins and have a general structure that includes an amino group (-NH2), a carboxyl group (-COOH), a hydrogen atom, and a side chain (R group) that is unique to each amino acid. The side chain determines the properties of the amino acid. Acidic amino acids are those that have an additional carboxyl group in their side chain, which can donate a proton (H+) and thus act as an acid. This means that acidic amino acids have at least two carboxyl groups in total. Now let's examine the pairs of amino acids given in the options: (a) Aspartic acid and glutamic acid: Both of these amino acids have an additional carboxyl group in their side chains. Aspartic acid has a side chain of -CH2-COOH, and glutamic acid has a side chain of -CH2-CH2-COOH. This means that both aspartic acid and glutamic acid have two carboxyl groups and one amino group per molecule, fitting the description of acidic amino acids. (b) Lysine and arginine: These are basic amino acids, not acidic. Lysine has a side chain of -CH2-CH2-CH2-CH2-NH2, and arginine has a side chain that includes a guanidinium group, which is positively charged at physiological pH. They do not have an additional carboxyl group, so they do not fit the description of acidic amino acids. (c) Glycine and alanine: These are neutral amino acids. Glycine has a side chain of a single hydrogen atom (making it the simplest amino acid), and alanine has a side chain of -CH3. Neither of these amino acids has an additional carboxyl group, so they are not acidic amino acids. (d) Both (a) and (b): Since (b) is incorrect, this option is also incorrect. Therefore, the correct answer is: (a) Aspartic acid, glutamic acid These are the two amino acids that consist of acidic amino acids, as they both contain two carboxyl groups and one amino group per molecule.

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Acidic amino acids have two -COOH groups and one -NH2 group per molecule. Select the pair that consists of acidic amino acids. (a) Aspartic acid, glutamic acid (b) Lysine, arginine (c) Glycine, alanine (d) Both (a) and (b)

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