USMLE STEP 1 BIOCHEMISTRY – METABOLISM
(320 QUESTIONS AND ANSWERS) 2024/2025
UPDATED LATEST GRADED A+.
What occurs in the mitochondria - Solution - Oxidative phosphorylation
- Fatty acid beta oxidation
- Acetyl-CoA production
- Ketogenesis
- TCA cycle
What occurs in the cytoplasm? - Solution - 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? - Solution (HUGs
take two)
Heme synthesis
Urea cycle
Gluconeogenesis
Dehydrogenases - Solution Oxidation-reduction reactions
Carboxylases - Solution Add a CO2 group with the help of biotin
Mutases - Solution Relocates functional group
Anabolic pathways - Solution build
Require both ATP and NADH
Catabolic pathways - Solution break down
Produce both ATP and NADH
,Carried in Activated Form: TPP (thiamine pyrophosphate) - Solution
Aldehydes
Carried in Activated Form: S-adenosylmethionine (SAM) - Solution CH3
Carried in Activated Form: THF - Solution 1-carbon units
Carried in Activated Form: Biotin - Solution CO2
Carried in Activated Form: CoA - Solution Acyl groups
Carried in Activated Form: Lipoamide - Solution Acyl groups
NAD+ is used in: - Solution Catabolic processes
NADPH is a product of: - Solution HMP Shunt (Pentose Phosphate
Pathway)
NADPH is used in: - Solution (Anabolic processes)
Glutathione Reductase
Respiratory Burst
Cytochrome P450
Nitric Oxide Formation
Insulin-Dependent Glucose Transporters - Solution GLUT-4
Insulin-Independent Glucose Transporters - Solution GLUT-1
GLUT-2
GLUT-3
GLUT-5
GLUT-1 - Solution - Found in:
Brain
RBCs
Cornea
- High affinity, basal glucose uptake
GLUT-2 - Solution - Found in:
,Kidney
Small Intestine
Liver
Beta cells of pancreas
- Bidirectional, Low affinity, Post-prandial action
GLUT-3 - Solution - Found in:
Brain
Placenta
Testes
GLUT-4 - Solution - Found in:
Adipose tissue
Striated muscle
- Exercise increases expression
- Insulin stimulates translocation from cytoplasm to membrane
GLUT-5 - Solution - Found in:
Spermatocytes
GI Tract
- Used for Fructose**
At low glucose concentrations, glucose is stored in ________. - Solution
Tissues
At high glucose concentrations, glucose is stored in ________. - Solution
Liver
Hexokinase (1-3)
a. Location
b. Km
c. Vmax
d. Induced by Insulin?
e. Feedback inhibited by Glucose-6-P?
f. Gene Mutation associated w/ MODY? - Solution a. All tissues (except
beta cell of pancreas and liver)
b. Low (high affinity)
, c. Low (lower capacity)
d. No
e. Yes
f. No
Glucokinase (Hexokinase 4)
a. Location
b. Km
c. Vmax
d. Induced by Insulin?
e. Feedback inhibited by Glucose-6-P?
f. Gene Mutation associated w/ MODY? - Solution a. Pancreatic Beta cells
and Liver
b. High (low affinity)
c. High (higher capacity)
d. Yes
e. No
f. Yes
What inhibits Glucokinase? - Solution Fructose-6-P
What inhibits Hexokinase? - Solution Glucose-6-P
Net Glycolysis yields... - Solution 2 Pyruvate
2 ATP
2 NADH
Phosphofructokinase-1 (PFK1) - Solution Converts Fructose-6-P to
Fructose-1,6-bisphosphate
Stimulators of PFK1 - Solution AMP
Fructose-2,6-bisphosphate
Inhibitors of PFK1 - Solution ATP
Citrate
Phosphoglycerate Kinase - Solution Converts 1,3-bisphosphoglycerate to
3-Phosphoglycerate, yielding 1 ATP
- Occurs in glycolysis
(320 QUESTIONS AND ANSWERS) 2024/2025
UPDATED LATEST GRADED A+.
What occurs in the mitochondria - Solution - Oxidative phosphorylation
- Fatty acid beta oxidation
- Acetyl-CoA production
- Ketogenesis
- TCA cycle
What occurs in the cytoplasm? - Solution - 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? - Solution (HUGs
take two)
Heme synthesis
Urea cycle
Gluconeogenesis
Dehydrogenases - Solution Oxidation-reduction reactions
Carboxylases - Solution Add a CO2 group with the help of biotin
Mutases - Solution Relocates functional group
Anabolic pathways - Solution build
Require both ATP and NADH
Catabolic pathways - Solution break down
Produce both ATP and NADH
,Carried in Activated Form: TPP (thiamine pyrophosphate) - Solution
Aldehydes
Carried in Activated Form: S-adenosylmethionine (SAM) - Solution CH3
Carried in Activated Form: THF - Solution 1-carbon units
Carried in Activated Form: Biotin - Solution CO2
Carried in Activated Form: CoA - Solution Acyl groups
Carried in Activated Form: Lipoamide - Solution Acyl groups
NAD+ is used in: - Solution Catabolic processes
NADPH is a product of: - Solution HMP Shunt (Pentose Phosphate
Pathway)
NADPH is used in: - Solution (Anabolic processes)
Glutathione Reductase
Respiratory Burst
Cytochrome P450
Nitric Oxide Formation
Insulin-Dependent Glucose Transporters - Solution GLUT-4
Insulin-Independent Glucose Transporters - Solution GLUT-1
GLUT-2
GLUT-3
GLUT-5
GLUT-1 - Solution - Found in:
Brain
RBCs
Cornea
- High affinity, basal glucose uptake
GLUT-2 - Solution - Found in:
,Kidney
Small Intestine
Liver
Beta cells of pancreas
- Bidirectional, Low affinity, Post-prandial action
GLUT-3 - Solution - Found in:
Brain
Placenta
Testes
GLUT-4 - Solution - Found in:
Adipose tissue
Striated muscle
- Exercise increases expression
- Insulin stimulates translocation from cytoplasm to membrane
GLUT-5 - Solution - Found in:
Spermatocytes
GI Tract
- Used for Fructose**
At low glucose concentrations, glucose is stored in ________. - Solution
Tissues
At high glucose concentrations, glucose is stored in ________. - Solution
Liver
Hexokinase (1-3)
a. Location
b. Km
c. Vmax
d. Induced by Insulin?
e. Feedback inhibited by Glucose-6-P?
f. Gene Mutation associated w/ MODY? - Solution a. All tissues (except
beta cell of pancreas and liver)
b. Low (high affinity)
, c. Low (lower capacity)
d. No
e. Yes
f. No
Glucokinase (Hexokinase 4)
a. Location
b. Km
c. Vmax
d. Induced by Insulin?
e. Feedback inhibited by Glucose-6-P?
f. Gene Mutation associated w/ MODY? - Solution a. Pancreatic Beta cells
and Liver
b. High (low affinity)
c. High (higher capacity)
d. Yes
e. No
f. Yes
What inhibits Glucokinase? - Solution Fructose-6-P
What inhibits Hexokinase? - Solution Glucose-6-P
Net Glycolysis yields... - Solution 2 Pyruvate
2 ATP
2 NADH
Phosphofructokinase-1 (PFK1) - Solution Converts Fructose-6-P to
Fructose-1,6-bisphosphate
Stimulators of PFK1 - Solution AMP
Fructose-2,6-bisphosphate
Inhibitors of PFK1 - Solution ATP
Citrate
Phosphoglycerate Kinase - Solution Converts 1,3-bisphosphoglycerate to
3-Phosphoglycerate, yielding 1 ATP
- Occurs in glycolysis
