BCH 361 EXAM 1 QUESTIONS WITH
CORRECT DETAILED ANSWERS
(100% CORRECT)
Peptide bond - Answer-amino acid polymerization through dehydration reaction
amide bond
not energetically favored (catalyzed)
n-terminus - Answer-free amino group
c-terminus - Answer-free carboxyl group
backbone of peptides - Answer-N, alpha-C, C from each amino acid to form linear chain
side chain - Answer-R group
disulfide bond - Answer-cysteins in a polypetide bond that are oxidized
rotation
peptide plane - Answer-peptide bond prevents ___ and maintains the ___
___ conformation is always favored due to lack of steric clashes - Answer-trans
alpha-C and N bond rotation - Answer-φ (phi)
alpha C and C bond rotation - Answer-ψ (psi)
alpha helix - Answer-backbone folds into helical conformation
ψ = -60
φ = -70 to -100
H-bonds between C=O and N-H; separated by 3 residues - Answer-alpha helices are
stabilized by ___
parallel - Answer-direction of h-bonds in alpha helix are ___ to the helical axis
destabilize due to steric hindrance - Answer-Val, Thr, Ile in an alpha-helix
compete for H-bonding between the main chain NH and CO groups - Answer-Ser, Asp,
Asn in alpha-helix
Pro in alpha-helix - Answer-alpha-helix breaker
, occurs at the end
has no free NH group available for hydrogen bonding
Gly in alpha-helix - Answer-too flexible
Beta-sheets - Answer-formed by adjacent Beta-strands lying next to one another
through hydrogen bonds
side chains are placed above or below
Φ=-70 to -100
ψ=90 to 110
secondary structure forms - Answer-alpha helices and beta sheets
anti-parallel beta sheets - Answer-neighboring strands have different orientation
(h-bond lines are parallel)
parallel beta sheets - Answer-neighboring strands have same orientation
(h-bond lines are not parallel)
tertiary proteins are either - Answer-fibrous or globular
fibrous - Answer-simple tertiary structures with extensive secondary structures
rod - Answer-fibrous tertiary structure with extensive helix structures
sheet - Answer-fibrous tertiary structure with extensive sheet structures
fibrous proteins provide - Answer-structural support for cell tissue (alpha-keratin and
collagen)
alpha-keratin is found in - Answer-found in wool, hair, nail, horn, feather, and epithelial
cells
alpha-keratin is composed of - Answer-two right-handed alpha helices (stabilized by
intra-strand H-bond) intertwined to form a left-handed super helix called a coiled-coil
the two helices interact with in alpha keratin - Answer-ionic bonds, van der Waal
interactions, and occasional disulfide bonds
collagen is found in - Answer-connective tissue (skin, bone, tendons, cartilage, and
teeth)
collagen is composed of - Answer-three interwined helical (NOT alpha-helices)
polypeptide chains
form a left-handed super-helical cable
CORRECT DETAILED ANSWERS
(100% CORRECT)
Peptide bond - Answer-amino acid polymerization through dehydration reaction
amide bond
not energetically favored (catalyzed)
n-terminus - Answer-free amino group
c-terminus - Answer-free carboxyl group
backbone of peptides - Answer-N, alpha-C, C from each amino acid to form linear chain
side chain - Answer-R group
disulfide bond - Answer-cysteins in a polypetide bond that are oxidized
rotation
peptide plane - Answer-peptide bond prevents ___ and maintains the ___
___ conformation is always favored due to lack of steric clashes - Answer-trans
alpha-C and N bond rotation - Answer-φ (phi)
alpha C and C bond rotation - Answer-ψ (psi)
alpha helix - Answer-backbone folds into helical conformation
ψ = -60
φ = -70 to -100
H-bonds between C=O and N-H; separated by 3 residues - Answer-alpha helices are
stabilized by ___
parallel - Answer-direction of h-bonds in alpha helix are ___ to the helical axis
destabilize due to steric hindrance - Answer-Val, Thr, Ile in an alpha-helix
compete for H-bonding between the main chain NH and CO groups - Answer-Ser, Asp,
Asn in alpha-helix
Pro in alpha-helix - Answer-alpha-helix breaker
, occurs at the end
has no free NH group available for hydrogen bonding
Gly in alpha-helix - Answer-too flexible
Beta-sheets - Answer-formed by adjacent Beta-strands lying next to one another
through hydrogen bonds
side chains are placed above or below
Φ=-70 to -100
ψ=90 to 110
secondary structure forms - Answer-alpha helices and beta sheets
anti-parallel beta sheets - Answer-neighboring strands have different orientation
(h-bond lines are parallel)
parallel beta sheets - Answer-neighboring strands have same orientation
(h-bond lines are not parallel)
tertiary proteins are either - Answer-fibrous or globular
fibrous - Answer-simple tertiary structures with extensive secondary structures
rod - Answer-fibrous tertiary structure with extensive helix structures
sheet - Answer-fibrous tertiary structure with extensive sheet structures
fibrous proteins provide - Answer-structural support for cell tissue (alpha-keratin and
collagen)
alpha-keratin is found in - Answer-found in wool, hair, nail, horn, feather, and epithelial
cells
alpha-keratin is composed of - Answer-two right-handed alpha helices (stabilized by
intra-strand H-bond) intertwined to form a left-handed super helix called a coiled-coil
the two helices interact with in alpha keratin - Answer-ionic bonds, van der Waal
interactions, and occasional disulfide bonds
collagen is found in - Answer-connective tissue (skin, bone, tendons, cartilage, and
teeth)
collagen is composed of - Answer-three interwined helical (NOT alpha-helices)
polypeptide chains
form a left-handed super-helical cable
