Special Sub-Topic: 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.
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