BIOL 200 UBC MIDTERM EXAM
QUESTIONS AND ANSWERS GRADED A+
2026
What bonds form in a primary protein structure? - ANS covalent bonds between the
backbone, peptide bonds
What bonds form in a secondary protein structure? - ANS non covalent bonds between
backbone
What bonds form in a tertiary protein structure? - ANS covalent bonds between R groups (i.e.
disulfide), non-covalent bonds between backbone, R groups
What bonds form in a quaternary protein structure? - ANS -covalent bonds between R groups
(i.e. disulfide), non-covalent bonds between backbone, R groups
-between 2+ polypeptides
How is a peptide bond formed? - ANS condensation reaction between alpha amino group of
one amino acid and carboxyl group of another
Why are some folding patterns not obtainable by primary structures? - ANS resonance
between C-O and C-N constrains flexibility, no free rotation around C-N axis
@COPYRIGHT 2026/2027 ALL RIGHTS RESERVED
1
, What bonds stabilize primary structures? - ANS peptide bonds
What bonds stabilize secondary structures? - ANS H-bonds between N-H, C=O groups
What types of structures result from secondary protein folding? - ANS alpha helix, beta sheet
Describe the bonds of an alpha helix. - ANS carbonyl forms H-bond with H from N-H of a
residue, 4 residues further on sequence (in same chain), side chains point outward
Describe the bonds of a beta sheet. - ANS polypeptide folds back on itself, H-bonds form
between N-H and C=O on neighbouring polypeptide strands, side chains project upwards &
downwards
What factors determine which structure forms in secondary folding? - ANS interactions
between side chains of amino acid residues in polypeptide such as: steric hinderance, charge
repulsion, proline presence, presence of other chem groups
What bonds stabilize tertiary structures? - ANS ionic bonds between side chains, H-bonds,
LDF (weaker so need more to stabilize), covalent disulfide bond between cysteine
How does hydrophobic interactions take part in tertiary formation? - ANS most stable when
hydrophobic residues face inwards, surrounded by other parts of the protein
What bonds stabilize quaternary structures? - ANS ionic bonds between side chains, H-
bonds, LDF, disulfide bonds
Describe the structure of quaternary folding. - ANS multiple polypeptide chains, ea. a
subunit, form a dimer, tetramer, etc., can be all same polypeptide or different
@COPYRIGHT 2026/2027 ALL RIGHTS RESERVED
2
QUESTIONS AND ANSWERS GRADED A+
2026
What bonds form in a primary protein structure? - ANS covalent bonds between the
backbone, peptide bonds
What bonds form in a secondary protein structure? - ANS non covalent bonds between
backbone
What bonds form in a tertiary protein structure? - ANS covalent bonds between R groups (i.e.
disulfide), non-covalent bonds between backbone, R groups
What bonds form in a quaternary protein structure? - ANS -covalent bonds between R groups
(i.e. disulfide), non-covalent bonds between backbone, R groups
-between 2+ polypeptides
How is a peptide bond formed? - ANS condensation reaction between alpha amino group of
one amino acid and carboxyl group of another
Why are some folding patterns not obtainable by primary structures? - ANS resonance
between C-O and C-N constrains flexibility, no free rotation around C-N axis
@COPYRIGHT 2026/2027 ALL RIGHTS RESERVED
1
, What bonds stabilize primary structures? - ANS peptide bonds
What bonds stabilize secondary structures? - ANS H-bonds between N-H, C=O groups
What types of structures result from secondary protein folding? - ANS alpha helix, beta sheet
Describe the bonds of an alpha helix. - ANS carbonyl forms H-bond with H from N-H of a
residue, 4 residues further on sequence (in same chain), side chains point outward
Describe the bonds of a beta sheet. - ANS polypeptide folds back on itself, H-bonds form
between N-H and C=O on neighbouring polypeptide strands, side chains project upwards &
downwards
What factors determine which structure forms in secondary folding? - ANS interactions
between side chains of amino acid residues in polypeptide such as: steric hinderance, charge
repulsion, proline presence, presence of other chem groups
What bonds stabilize tertiary structures? - ANS ionic bonds between side chains, H-bonds,
LDF (weaker so need more to stabilize), covalent disulfide bond between cysteine
How does hydrophobic interactions take part in tertiary formation? - ANS most stable when
hydrophobic residues face inwards, surrounded by other parts of the protein
What bonds stabilize quaternary structures? - ANS ionic bonds between side chains, H-
bonds, LDF, disulfide bonds
Describe the structure of quaternary folding. - ANS multiple polypeptide chains, ea. a
subunit, form a dimer, tetramer, etc., can be all same polypeptide or different
@COPYRIGHT 2026/2027 ALL RIGHTS RESERVED
2
