BCMB 401 Exam 1 Questions & Answers
2025/2026
Define the term covalent bond and discuss the bond strength. - ANSWERS- covalent bond: two
non-metals sharing electrons (polar = unequal, nonpolar = equal)
- strength of bond inversely proportional to atomic weight (strength increases as weight
decreases)
Define the term resonance structures and discuss how resonance structures affect the
thermodynamic stability of organic molecules. - ANSWERS- resonance structures: two or more
Lewis structures that collectively describe the fractional bonding and/or fractional charges of a
single polyatomic ion or molecule
- resonance makes an organic molecule more stable
Compare covalent bonds with non-covalent bonds. - ANSWERS- covalent bonds keep atoms
tightly together, have a high bond energy, and are stabilized by resonance
- noncovalent bonds are weak and transient with lower bond energy
Name four types of non-covalent bonds and describe their characteristics. - ANSWERS1)
Electrostatic interactions (dipole-dipole):
- attractive forces between oppositely charged particles
- high electric constant means weakening ionic interactions and indicates a more polar solution
2) Hydrogen bonds:
- weak, transient bonds between an electronegative acceptor (O or N) and and H covalently
bonded to an electronegative donor
3) van der Waals interactions:
- occur between molecules physically close to one another when their electron asymmetries
(due to polarization) match up
, - weak but additive over a large area
4) Hydrophobic interactions:
- immobile clathrate shell of water forms around nonpolar molecules in water, limiting
interactions
- association of nonpolar molecules decreases entropy, which then releases bound clathrate
water back into the solvent and raises entropy
Explain the origin of hydrophobic attractions between nonpolar molecules and give examples of
their importance in biochemical interactions. - ANSWERS- nonpolar molecules cannot
participate in hydrogen bonding or ionic interactions, and so nonpolar molecules interacting
with polar water molecules are unfavorable
- clathrate shells of water will surround nonpolar molecules, decreasing entropy
- as nonpolar molecules inside clathrate shells associate with one another, clathrate bound
water molecules are released, increasing entropy
What are the two important points about non-covalent bonds from biochemical perspective? -
ANSWERS1) hydrogen bonding
2) ???
What would happen if covalent bonds were used for biomolecular recognition instead of non-
covalent bonds? - ANSWERS- biomolecular recognition is highly specific and reversible,
something that is easier when working with many weaker non-covalent interactions
- covalent bonds take a lot of energy to break, which wouldn't be efficient for biomolecular
recognition
Describe the effect of temperature, pH, and atom electronegativity on the strength of covalent
and noncovalent bonds. - ANSWERS- increased temperature breaks both covalent and
noncovalent bonds
- changing pH can break noncovalent bonds
2025/2026
Define the term covalent bond and discuss the bond strength. - ANSWERS- covalent bond: two
non-metals sharing electrons (polar = unequal, nonpolar = equal)
- strength of bond inversely proportional to atomic weight (strength increases as weight
decreases)
Define the term resonance structures and discuss how resonance structures affect the
thermodynamic stability of organic molecules. - ANSWERS- resonance structures: two or more
Lewis structures that collectively describe the fractional bonding and/or fractional charges of a
single polyatomic ion or molecule
- resonance makes an organic molecule more stable
Compare covalent bonds with non-covalent bonds. - ANSWERS- covalent bonds keep atoms
tightly together, have a high bond energy, and are stabilized by resonance
- noncovalent bonds are weak and transient with lower bond energy
Name four types of non-covalent bonds and describe their characteristics. - ANSWERS1)
Electrostatic interactions (dipole-dipole):
- attractive forces between oppositely charged particles
- high electric constant means weakening ionic interactions and indicates a more polar solution
2) Hydrogen bonds:
- weak, transient bonds between an electronegative acceptor (O or N) and and H covalently
bonded to an electronegative donor
3) van der Waals interactions:
- occur between molecules physically close to one another when their electron asymmetries
(due to polarization) match up
, - weak but additive over a large area
4) Hydrophobic interactions:
- immobile clathrate shell of water forms around nonpolar molecules in water, limiting
interactions
- association of nonpolar molecules decreases entropy, which then releases bound clathrate
water back into the solvent and raises entropy
Explain the origin of hydrophobic attractions between nonpolar molecules and give examples of
their importance in biochemical interactions. - ANSWERS- nonpolar molecules cannot
participate in hydrogen bonding or ionic interactions, and so nonpolar molecules interacting
with polar water molecules are unfavorable
- clathrate shells of water will surround nonpolar molecules, decreasing entropy
- as nonpolar molecules inside clathrate shells associate with one another, clathrate bound
water molecules are released, increasing entropy
What are the two important points about non-covalent bonds from biochemical perspective? -
ANSWERS1) hydrogen bonding
2) ???
What would happen if covalent bonds were used for biomolecular recognition instead of non-
covalent bonds? - ANSWERS- biomolecular recognition is highly specific and reversible,
something that is easier when working with many weaker non-covalent interactions
- covalent bonds take a lot of energy to break, which wouldn't be efficient for biomolecular
recognition
Describe the effect of temperature, pH, and atom electronegativity on the strength of covalent
and noncovalent bonds. - ANSWERS- increased temperature breaks both covalent and
noncovalent bonds
- changing pH can break noncovalent bonds
