BIOCHEMISTRY ACTUAL STEP ONE
EXAMINATION 2026 FULL ANSWERS
GRADED A+
⩥ Citrate Synthase. Answer: Combines Oxaloacetate and Acetyl-CoA to
make Citrate
⩥ Rotenone. Answer: Inhibits Complex I of ETC
*NADH dehydrogenase*
This is a form of *pesticide*
⩥ Antimycin A. Answer: Inhibits Complex III of ETC
*Cytochrome b/c1*
⩥ Cyanide (CN). Answer: Inhibits Complex IV of ETC
*Cytochrome A*
Cyanide comes from *Nitroprusside* administration. Ex. burning
furniture, mining
,⩥ Carbon Monoxide (CO). Answer: Inhibits Complex IV of ETC
*Cytochrome A*
⩥ Oligomycin (macrolide antiobiotic). Answer: Inhibits Complex V of
ETC
*ATPase complex*
⩥ 2,4-Dinitrophenol (2,4-DNP)
Aspirin
Thermogenin. Answer: Uncoupling Agent (used illicitly for weight loss)
Will increase permeability of membrane in ETC thus causing a drop in
the proton gradient and increases O2 consumption.
ATP synthesis stops but ETC continues. *Heat produced* from wasted
energy.
Also seen with *Aspirin* overdose and *thermogenin* in brown fat
(animals)
,⩥ Phosphoenolpyruvate (PEP) Carboxykinase. Answer:
Gluconeogenesis:
Converts Oxaloacetate to PEP in *Cytosol*
Requires GTP
⩥ Fructose-1,6-Biphosphatase. Answer: Gluconeogenesis:
Converts Fructose-1,6-biphosphate to Fructose-6-phosphate in *cytosol*
*Rate Limiting Step*
⩥ Glucose-6-Phosphatase. Answer: Gluconeogenesis:
Converts Glucose-6-phosphate (G6P) to glucose
Occurs in *Endoplasmic Reticulum*
This enzymes is *NOT FOUND* in *MUSCLE* therefore muscles
cannot participate in gluconeogenesis.
, ⩥ Glucose-6-P Dehydrogenase. Answer: Pentose Phosphate Pathway
Converts Glucose 6 -Phosphate (G6P) to Ribulose-5-P and *NADPH*
Needed for reductive reactions and R5P can be used for nucleotide
synthesis.
NADPH is used to convert oxidized glutathione to reduced glutathione
via Glutathione Reductase
⩥ Glucose-6-P Dehydrogenase Deficiency. Answer: Unable to produce
NADPH thus unable to reduce glutathione and detoxify free radicals.
This causes *hemolytic anemia* in *Red Blood Cells* due to poor RBC
defence. against oxidizing agents.
Ex. Fava Beans, Sulfonamides, Primaquine, Anti-TB drugs, Infection
X-linked Recessive
Histology: Heinz Bodies + Bite Cells
⩥ Glutathione Peroxidase. Answer: Converts H2O2 (hydrogen peroxide)
to water
Necessary to neutralize reactive oxygen species
EXAMINATION 2026 FULL ANSWERS
GRADED A+
⩥ Citrate Synthase. Answer: Combines Oxaloacetate and Acetyl-CoA to
make Citrate
⩥ Rotenone. Answer: Inhibits Complex I of ETC
*NADH dehydrogenase*
This is a form of *pesticide*
⩥ Antimycin A. Answer: Inhibits Complex III of ETC
*Cytochrome b/c1*
⩥ Cyanide (CN). Answer: Inhibits Complex IV of ETC
*Cytochrome A*
Cyanide comes from *Nitroprusside* administration. Ex. burning
furniture, mining
,⩥ Carbon Monoxide (CO). Answer: Inhibits Complex IV of ETC
*Cytochrome A*
⩥ Oligomycin (macrolide antiobiotic). Answer: Inhibits Complex V of
ETC
*ATPase complex*
⩥ 2,4-Dinitrophenol (2,4-DNP)
Aspirin
Thermogenin. Answer: Uncoupling Agent (used illicitly for weight loss)
Will increase permeability of membrane in ETC thus causing a drop in
the proton gradient and increases O2 consumption.
ATP synthesis stops but ETC continues. *Heat produced* from wasted
energy.
Also seen with *Aspirin* overdose and *thermogenin* in brown fat
(animals)
,⩥ Phosphoenolpyruvate (PEP) Carboxykinase. Answer:
Gluconeogenesis:
Converts Oxaloacetate to PEP in *Cytosol*
Requires GTP
⩥ Fructose-1,6-Biphosphatase. Answer: Gluconeogenesis:
Converts Fructose-1,6-biphosphate to Fructose-6-phosphate in *cytosol*
*Rate Limiting Step*
⩥ Glucose-6-Phosphatase. Answer: Gluconeogenesis:
Converts Glucose-6-phosphate (G6P) to glucose
Occurs in *Endoplasmic Reticulum*
This enzymes is *NOT FOUND* in *MUSCLE* therefore muscles
cannot participate in gluconeogenesis.
, ⩥ Glucose-6-P Dehydrogenase. Answer: Pentose Phosphate Pathway
Converts Glucose 6 -Phosphate (G6P) to Ribulose-5-P and *NADPH*
Needed for reductive reactions and R5P can be used for nucleotide
synthesis.
NADPH is used to convert oxidized glutathione to reduced glutathione
via Glutathione Reductase
⩥ Glucose-6-P Dehydrogenase Deficiency. Answer: Unable to produce
NADPH thus unable to reduce glutathione and detoxify free radicals.
This causes *hemolytic anemia* in *Red Blood Cells* due to poor RBC
defence. against oxidizing agents.
Ex. Fava Beans, Sulfonamides, Primaquine, Anti-TB drugs, Infection
X-linked Recessive
Histology: Heinz Bodies + Bite Cells
⩥ Glutathione Peroxidase. Answer: Converts H2O2 (hydrogen peroxide)
to water
Necessary to neutralize reactive oxygen species
