BIOCHEMISTRY USMLE COMPREHENSIVE STUDY GUIDE 2026 QUESTIONS WITH SOLUTIONS GRADED A+

BIOCHEMISTRY STEP 1 FINAL PAPER 2026
COMPLETE ANSWERS GRADED A+

⩥ What occurs in the cytoplasm? Answer: - Glycolysis
- Fatty acid synthesis
- Cholesterol synthesis
- Protein synthesis (RER)
- Steroid synthesis (SER)
- HMP Shunt (Pentose Phosphate Pathway)


⩥ What occurs in both the mitochondria and cytoplasm? Answer:
(HUGs take two)


Heme synthesis
Urea cycle
Gluconeogenesis


⩥ Dehydrogenases Answer: Oxidation-reduction reactions


⩥ Carboxylases Answer: Add a CO2 group with the help of biotin


⩥ Mutases Answer: Relocates functional group

,⩥ Anabolic pathways Answer: build


Require both ATP and NADH


⩥ Catabolic pathways Answer: break down
Produce both ATP and NADH


⩥ Carried in Activated Form: TPP (thiamine pyrophosphate) Answer:
Aldehydes


⩥ Carried in Activated Form: S-adenosylmethionine (SAM) Answer:
CH3


⩥ Carried in Activated Form: THF Answer: 1-carbon units


⩥ Carried in Activated Form: Biotin Answer: CO2


⩥ Carried in Activated Form: CoA Answer: Acyl groups


⩥ Carried in Activated Form: Lipoamide Answer: Acyl groups

,⩥ NAD+ is used in: Answer: Catabolic processes


⩥ NADPH is a product of: Answer: HMP Shunt (Pentose Phosphate
Pathway)


⩥ NADPH is used in: Answer: (Anabolic processes)


Glutathione Reductase
Respiratory Burst
Cytochrome P450
Nitric Oxide Formation


⩥ Insulin-Dependent Glucose Transporters Answer: GLUT-4


⩥ Insulin-Independent Glucose Transporters Answer: GLUT-1
GLUT-2
GLUT-3
GLUT-5


⩥ GLUT-1 Answer: - Found in:
Brain
RBCs

, Cornea


- High affinity, basal glucose uptake


⩥ GLUT-2 Answer: - Found in:
Kidney
Small Intestine
Liver
Beta cells of pancreas


- Bidirectional, Low affinity, Post-prandial action


⩥ GLUT-3 Answer: - Found in:
Brain
Placenta
Testes


⩥ GLUT-4 Answer: - Found in:
Adipose tissue
Striated muscle


- Exercise increases expression