BIOCHEM 210 MODULE 3 EXAM 2026/2027| Portage
Learning | Amino Acids, Proteins and Enzymes
Questions And Answers
Question 1: What are the 20 standard amino acids, and what common
structural features do they share?
Answer: The 20 standard amino acids are the monomers used as building
blocks for proteins. At physiological pH (7.4), all contain an amine group
(NH₃⁺), a carboxylic acid group (COO⁻), and a hydrogen atom connected to
an alpha carbon, with varying R side chains that determine their unique
properties.
Question 2: How are amino acids classified based on their R groups?
Answer: Amino acids are grouped by charge, size, and polarity of their R
side chains.
Question 3: The formation of a peptide bond between two amino acids is
an example of what type of reaction?
Answer: Condensation reaction (also called dehydration synthesis).
Question 4: What is the primary structure of a protein?
,Answer: The primary structure refers to the order of amino acids covalently
bonded in a polypeptide chain, including disulfide bonds. The sequence is
written from N-terminus to C-terminus using one-letter or three-letter
abbreviations.
Question 5: What is a peptide bond?
Answer: A peptide bond is a covalent bond formed when two amino acids
join together through a condensation reaction between the carboxyl group
of one amino acid and the amino group of another.
Question 6: What are the four levels of protein structure?
Answer: Primary, secondary, tertiary, and quaternary structure.
Question 7: What is secondary structure?
Answer: Secondary structure examines the LOCAL 3D structure of amino
acid residues close in linear sequence. It includes alpha-helices, beta-sheets,
and beta-turns.
Question 8: What is an alpha-helix?
,Answer: Coiled structures of amino acids where backbone atoms form
hydrogen bonds to stabilize the sequence. There is no space in the interior.
Common residues include alanine, arginine, and leucine.
Question 9: Roughly how many amino acids are there in one turn of an
alpha helix?
Answer: 3.6 amino acids per turn.
Question 10: What is a beta-sheet?
Answer: A repetitive sheet-like structure of amino acids with adjacent side
chains as far apart as possible. Sheets form strands that hydrogen-bond
together, and can be parallel or anti-parallel.
Question 11: What is the difference between parallel and anti-parallel
beta-sheets?
Answer: Anti-parallel beta-sheets form when one beta strand ends and the
sequence turns back on itself, with strands going in opposite directions
(repeat every 7 angstroms). Parallel beta-sheets have strands going in the
same direction (repeat every 6.5 angstroms).
, Question 12: What is a beta-turn?
Answer: A 4-residue unit that turns 180 degrees, permitting proteins to
form secondary structures immediately adjacent to one another.
Question 13: What is a motif?
Answer: Collections of stable groups of secondary structures (e.g., helix-
turn-helix) that lead to function. Motifs are between secondary and tertiary
structures in the hierarchy of protein organization.
Question 14: What is tertiary structure?
Answer: The overall 3-D structure of a folded polypeptide, stabilized by
noncovalent forces and disulfide bonds. May include prosthetic groups.
Question 15: What is a prosthetic group?
Answer: A non-amino acid portion of a molecule necessary for structure
and function of the protein.
Question 16: What is quaternary structure?
Learning | Amino Acids, Proteins and Enzymes
Questions And Answers
Question 1: What are the 20 standard amino acids, and what common
structural features do they share?
Answer: The 20 standard amino acids are the monomers used as building
blocks for proteins. At physiological pH (7.4), all contain an amine group
(NH₃⁺), a carboxylic acid group (COO⁻), and a hydrogen atom connected to
an alpha carbon, with varying R side chains that determine their unique
properties.
Question 2: How are amino acids classified based on their R groups?
Answer: Amino acids are grouped by charge, size, and polarity of their R
side chains.
Question 3: The formation of a peptide bond between two amino acids is
an example of what type of reaction?
Answer: Condensation reaction (also called dehydration synthesis).
Question 4: What is the primary structure of a protein?
,Answer: The primary structure refers to the order of amino acids covalently
bonded in a polypeptide chain, including disulfide bonds. The sequence is
written from N-terminus to C-terminus using one-letter or three-letter
abbreviations.
Question 5: What is a peptide bond?
Answer: A peptide bond is a covalent bond formed when two amino acids
join together through a condensation reaction between the carboxyl group
of one amino acid and the amino group of another.
Question 6: What are the four levels of protein structure?
Answer: Primary, secondary, tertiary, and quaternary structure.
Question 7: What is secondary structure?
Answer: Secondary structure examines the LOCAL 3D structure of amino
acid residues close in linear sequence. It includes alpha-helices, beta-sheets,
and beta-turns.
Question 8: What is an alpha-helix?
,Answer: Coiled structures of amino acids where backbone atoms form
hydrogen bonds to stabilize the sequence. There is no space in the interior.
Common residues include alanine, arginine, and leucine.
Question 9: Roughly how many amino acids are there in one turn of an
alpha helix?
Answer: 3.6 amino acids per turn.
Question 10: What is a beta-sheet?
Answer: A repetitive sheet-like structure of amino acids with adjacent side
chains as far apart as possible. Sheets form strands that hydrogen-bond
together, and can be parallel or anti-parallel.
Question 11: What is the difference between parallel and anti-parallel
beta-sheets?
Answer: Anti-parallel beta-sheets form when one beta strand ends and the
sequence turns back on itself, with strands going in opposite directions
(repeat every 7 angstroms). Parallel beta-sheets have strands going in the
same direction (repeat every 6.5 angstroms).
, Question 12: What is a beta-turn?
Answer: A 4-residue unit that turns 180 degrees, permitting proteins to
form secondary structures immediately adjacent to one another.
Question 13: What is a motif?
Answer: Collections of stable groups of secondary structures (e.g., helix-
turn-helix) that lead to function. Motifs are between secondary and tertiary
structures in the hierarchy of protein organization.
Question 14: What is tertiary structure?
Answer: The overall 3-D structure of a folded polypeptide, stabilized by
noncovalent forces and disulfide bonds. May include prosthetic groups.
Question 15: What is a prosthetic group?
Answer: A non-amino acid portion of a molecule necessary for structure
and function of the protein.
Question 16: What is quaternary structure?
