ACS BIOCHEMISTRY PRACTICE FINAL CORE
BIOCHEMICAL PATHWAYS AND MOLECULAR
STRUCTURE REVIEW 2026
◉ Protein-Protein Interfaces.
Answer: "Core" and "fringe" of the interfaces. Core is more
hydrophobic and is on the inside when interfaced. Fringe is more
hydrophilic.
◉ π-π Ring Stacking.
Answer: Weird interaction where aromatic rings stack on each other
in positive interaction.
◉ σ-hole.
Answer: Methyl group has area of diminished electron density in
center; attracts electronegative groups
◉ Fe Binding of O2.
Answer: Fe2+ binds to O2 reversible. Fe3+ has an additional +
charge and binds to O2 irreversibly. Fe3+ rusts in O2 rich
environments.
◉ Ka for Binding.
,Answer: Ka = [PL] / [P][L]
◉ ϴ-value in Binding.
Answer: ϴ = (bound / total)x100%
ϴ = [L] / ([L] + 1/Ka)
◉ Kd for binding.
Answer: Kd = [L] when 50% bound to protein.
Kd = 1/Ka
◉ High-Spin Fe.
Answer: Electrons are "spread out" and result in larger atom.
◉ Low-Spin Fe.
Answer: Electrons are less "spread out" and are compacted by
electron rich porphyrin ring.
◉ T-State.
Answer: Heme is in high-spin state. H2O is bound to heme.
◉ R-State.
Answer: Heme is in low-spin state. O2 is bound to heme.
,◉ O2 Binding Event.
Answer: O2 binds to T-state and changes the heme to R-state. Causes
a 0.4A movement of the iron.
◉ Hemoglobin Binding Curve.
Answer: 4 subunits present in hemoglobin that can be either T or R -
state. Cooperative binding leads to a sigmoidal curve.
◉ Binding Cooperativity.
Answer: When one subunit of hemoglobin changes from T to R-state
the other sites are more likely to change to R-state as well. Leads to
sigmoidal graph.
◉ Homotropic Regulation of Binding.
Answer: Where a regulatory molecule is also the enzyme's substrate.
◉ Heterotropic Regulation of Binding.
Answer: Where an allosteric regulator is present that is not the
enzyme's substrate.
◉ Hill Plot.
, Answer: Turns sigmoid into straight lines. Slope = n (# of binding
sites). Allows measurement of binding sites that are cooperative.
◉ pH and Binding Affinity (Bohr Affect).
Answer: As [H+] increases, Histidine group in hemoglobin becomes
more protonated and protein shifts to T-state. O2 binding affinity
decreases.
◉ CO2 binding in Hemoglobin.
Answer: Forms carbonic acid that shifts hemoglobin to T-state. O2
binding affinity decreases. Used in the peripheral tissues.
◉ BPG (2,3-bisphosphoglycerate).
Answer: Greatly reduces hemoglobin's affinity for O2 by binding
allosterically. Stabilizes T-state. Transfer of O2 can improve because
increased delivery in tissues can outweigh decreased binding in the
lungs.
◉ Michaelis-Menton Equation.
Answer: V0 = (Vmax[S]) / (Km + [S])
◉ Km in Michaelis-Menton.
Answer: Km = [S] when V0 = 0.5(Vmax)
BIOCHEMICAL PATHWAYS AND MOLECULAR
STRUCTURE REVIEW 2026
◉ Protein-Protein Interfaces.
Answer: "Core" and "fringe" of the interfaces. Core is more
hydrophobic and is on the inside when interfaced. Fringe is more
hydrophilic.
◉ π-π Ring Stacking.
Answer: Weird interaction where aromatic rings stack on each other
in positive interaction.
◉ σ-hole.
Answer: Methyl group has area of diminished electron density in
center; attracts electronegative groups
◉ Fe Binding of O2.
Answer: Fe2+ binds to O2 reversible. Fe3+ has an additional +
charge and binds to O2 irreversibly. Fe3+ rusts in O2 rich
environments.
◉ Ka for Binding.
,Answer: Ka = [PL] / [P][L]
◉ ϴ-value in Binding.
Answer: ϴ = (bound / total)x100%
ϴ = [L] / ([L] + 1/Ka)
◉ Kd for binding.
Answer: Kd = [L] when 50% bound to protein.
Kd = 1/Ka
◉ High-Spin Fe.
Answer: Electrons are "spread out" and result in larger atom.
◉ Low-Spin Fe.
Answer: Electrons are less "spread out" and are compacted by
electron rich porphyrin ring.
◉ T-State.
Answer: Heme is in high-spin state. H2O is bound to heme.
◉ R-State.
Answer: Heme is in low-spin state. O2 is bound to heme.
,◉ O2 Binding Event.
Answer: O2 binds to T-state and changes the heme to R-state. Causes
a 0.4A movement of the iron.
◉ Hemoglobin Binding Curve.
Answer: 4 subunits present in hemoglobin that can be either T or R -
state. Cooperative binding leads to a sigmoidal curve.
◉ Binding Cooperativity.
Answer: When one subunit of hemoglobin changes from T to R-state
the other sites are more likely to change to R-state as well. Leads to
sigmoidal graph.
◉ Homotropic Regulation of Binding.
Answer: Where a regulatory molecule is also the enzyme's substrate.
◉ Heterotropic Regulation of Binding.
Answer: Where an allosteric regulator is present that is not the
enzyme's substrate.
◉ Hill Plot.
, Answer: Turns sigmoid into straight lines. Slope = n (# of binding
sites). Allows measurement of binding sites that are cooperative.
◉ pH and Binding Affinity (Bohr Affect).
Answer: As [H+] increases, Histidine group in hemoglobin becomes
more protonated and protein shifts to T-state. O2 binding affinity
decreases.
◉ CO2 binding in Hemoglobin.
Answer: Forms carbonic acid that shifts hemoglobin to T-state. O2
binding affinity decreases. Used in the peripheral tissues.
◉ BPG (2,3-bisphosphoglycerate).
Answer: Greatly reduces hemoglobin's affinity for O2 by binding
allosterically. Stabilizes T-state. Transfer of O2 can improve because
increased delivery in tissues can outweigh decreased binding in the
lungs.
◉ Michaelis-Menton Equation.
Answer: V0 = (Vmax[S]) / (Km + [S])
◉ Km in Michaelis-Menton.
Answer: Km = [S] when V0 = 0.5(Vmax)
