- Which of the following is the general structure of an amino acid?
- A) R-CH(NH2)-COOH
- B) R-CH(NH2)-CH3
- C) R-CH(COOH)-COOH
- D) R-CH(NH2)-OH
Answer: A) R-CH(NH2)-COOH
- How many amino acids are commonly found in proteins?
- A) 10
- B) 15
- C) 20
- D) 25
Answer: C) 20
- Which amino acid has the simplest side chain (R group)?
- A) Alanine
- B) Glycine
- C) Serine
- D) Valine
Answer: B) Glycine
- Which of the following amino acids is not chiral?
- A) Alanine
- B) Glycine
- C) Serine
- D) Valine
Answer: B) Glycine
- What is the charge on a zwitterion of an amino acid at pH 7?
- A) +1
- B) -1
- C) 0
- D) +2
Answer: C) 0
- Which amino acid has a sulfur-containing side chain?
- A) Cysteine
- B) Serine
- C) Threonine
- D) Tyrosine
Answer: A) Cysteine
- Which amino acid has an aromatic side chain?
- A) Alanine
- B) Leucine
- C) Phenylalanine
- D) Valine
Answer: C) Phenylalanine
- Which amino acid has a basic side chain?
- A) Aspartic acid
- B) Glutamic acid
- C) Lysine
- D) Serine
Answer: C) Lysine
Short Answer Questions
- What is the general formula for an α-amino acid?
Answer: R-CH(NH2)-COOH
- Name the two amino acids that have an acidic side chain.
Answer: Aspartic acid and glutamic acid
- Which amino acid has a secondary amine in its side chain?
Answer: Proline
- What is the name of the reaction that forms a peptide bond between amino acids?
Answer: Condensation reaction
- What is the name of the reaction that breaks a peptide bond?
Answer: Hydrolysis
- What is the name of the amino acid that often starts protein synthesis?
Answer: Methionine
- Which amino acid has the highest melting point?
Answer: Proline
True/False Questions
- All amino acids are optically active.
True
- Amino acids are soluble in organic solvents.
False
- Amino acids can act as both acids and bases.
True
- Amino acids have low melting points.
False
- Amino acids are colorless crystalline solids.
True
Fill in the Blank Questions
- The side chain of an amino acid is represented by the letter “_”.
Answer: R
- The amino group of an amino acid is a “_” amine.
Answer: Primary
- The carboxyl group of an amino acid has a pKa of approximately “_”.
Answer: 2.2
- The amino group of an amino acid has a pKa of approximately “_”.
Answer: 9.4
- Amino acids can be classified based on the polarity of their “_”.
Answer: Side chain or R group
- The most common amino acids in proteins are “_” amino acids.
Answer: α (alpha)
PART II
Multiple Choice Questions
- Which of the following is the correct order of increasing pKa values for the amino group of amino acids?
- A) Glycine < Alanine < Serine
- B) Alanine < Glycine < Serine
- C) Serine < Glycine < Alanine
- D) Glycine < Serine < Alanine
Answer: B) Alanine < Glycine < Serine
- What is the charge on an amino acid at its isoelectric point?
- A) +1
- B) -1
- C) 0
- D) +2
Answer: C) 0
- Which amino acid has the highest boiling point?
- A) Glycine
- B) Alanine
- C) Valine
- D) Leucine
Answer: D) Leucine
- Which amino acid has a polar uncharged side chain?
- A) Serine
- B) Lysine
- C) Aspartic acid
- D) Phenylalanine
Answer: A) Serine
- Which amino acid has a non-polar aliphatic side chain?
- A) Isoleucine
- B) Histidine
- C) Arginine
- D) Tyrosine
Answer: A) Isoleucine
Short Answer Questions
- Name the amino acid that has a hydroxyl group in its side chain.
Answer: Serine
- What is the name of the amino acid that has a cyclic side chain?
Answer: Proline
- Which amino acid has a positively charged side chain at physiological pH?
Answer: Lysine
- Name the amino acid that has a negatively charged side chain at physiological pH.
Answer: Glutamic acid
- What is the name of the amino acid that has a thiol group in its side chain?
Answer: Cysteine
True/False Questions
- All amino acids have a tetrahedral carbon atom.
True
- Amino acids are soluble in water.
True
- Amino acids can form hydrogen bonds.
True
- Amino acids are optically inactive.
False
- Amino acids are amphoteric in nature.
True
Fill in the Blank Questions
- The carboxyl group of an amino acid has a pKa of approximately “_”.
Answer: 3.1
- The amino group of an amino acid has a pKa of approximately “_”.
Answer: 8.2
- The side chain of an amino acid is also known as the “_” group.
Answer: R
- The amino acid with the smallest side chain is “_”.
Answer: Glycine
- The amino acid with the largest side chain is “_”.
Answer: Tryptophan
- The amino acid with a positively charged side chain at physiological pH is “_”.
Answer: Arginine
- The amino acid with a negatively charged side chain at physiological pH is “_”.
Answer: Aspartic acid
- The amino acid with a polar uncharged side chain is “_”.
Answer: Asparagine
- The amino acid with a sulfur-containing side chain is “_”.
Answer: Methionine
- The amino acid with an aromatic side chain is “_”.
Answer: Tyrosine
- The amino acid with a basic side chain is “_”.
Answer: Histidine
- The amino acid with an acidic side chain is “_”.
Answer: Glutamic acid
- The amino acid with a non-polar aliphatic side chain is “_”.
Answer: Valine
- The amino acid with a polar uncharged side chain is “_”.
Answer: Threonine
- The amino acid with a non-polar aromatic side chain is “_”.
Answer: Phenylalanine