Special Sub-Topic: Amino Acids Click Here To Play: Amino Acids

Which of the following amino acids is the smallest of all amino acids?

Glycine. Each amino acid, aside from its name, has a three letter abbreviation and a one letter code. Glycine, gly, or G, is the smallest amino acid and fits in the non-polar group. Its "R" side chain is simply a hydrogen atom. Small amino acids are more commonly included in proteins than larger and more bulky amino acids.

Which of the following amino acids can form a special covalent bond called a disulfide bond?

Cysteine. Cysteine, cys, or C, is a sulfur containing non-polar amino acid. Two cysteine residues containing -SH groups form very stable covalent bonds called disulfides which stabilize and give structure to protein.

Which of the following amino acids is actually an imino acid?

Proline. Proline, pro, or P, has three methyl groups that attach to both the alpha carbon and the amino group forming a ring structure. An imino acid is any compound that contains both an imino (>C=NH) group and a carboxyl (-COOH) group.

Which of the following amino acids is the largest of all the amino acids?

Tryptophan. Tryptophan, trp, or W, is a member of the non-polar and aromatic group. Aromatic compounds contain one or more ring structures. As a large and bulky amino acid, it is less commonly included in proteins.

Which of the following amino acids is NOT positively charged?

Aspartic acid. Aspartic acid, asp or D, is an acidic and negatively charged amino acid that contains a carboxyl (-COO) group. Lysine, arginine and histidine are all basic amino acids and contain a positively charged -NH3 group.

The three letter abbreviation "asn" corresponds to which amino acid?

Asparagine. Asparagine, asn or N, is a polar amino acid which contains an amide (R-C(=O)-N-R) group. Alanine has the abbreviation Ala, arginine is Arg, and aspartic acid is Asp.

Of amino acids abbreviated "Lys", "Glu", "Trp", and "Gln", which is a basic amino acid with a positive charge?

Lysine. Lysine is abbreviated "lys" and oddly enough has the code "K". The code "L" is used by leucine.

Which of the following amino acids' side chains is a single methyl group?

Alanine. Alanine, ala or A, is a small non-polar amino acid and has a methyl, -CH3, group.

Which two of the following amino acids could form a ionic bond?

Aspartic acid and Lysine. An ionic bond will form between positively charged and negatively charged amino acids. Aspartic acid, asp, or D, is a negatively charged acidic amino acid while lysine, lys, or K, is a positively charged basic amino acid.

Which of the following amino acid(s) are polar?

All of these (Serine, Tyrosine, Arginine). Serine, ser, or S, and tyrosine, tyr, or Y, both contain a hydroxyl (-OH) group. Arginine, arg, or R, is a basic and positively charged amino acid. Of the 20 amino acids, 10 are polar and 10 are non-polar. Polar molecules are named so because they contribute either a positive or negative charge.