UNE Biochemistry Final, Final, Final Exam
Review UNE medical biochemistry| 290
Questions| With Complete Solutions
Course
UNE Biochemistry
1. Enzyme Kinetics
Question:
A certain enzyme follows Michaelis-Menten kinetics. If the VmaxV_{max}Vmax is 500 µmol/min
and the KmK_mKm is 5 mM, what is the reaction velocity when the substrate concentration is
2.5 mM?
Solution:
Using the Michaelis-Menten equation:
V=Vmax⋅[S]Km+[S]V = \frac{V_{max} \cdot [S]}{K_m + [S]}V=Km+[S]Vmax⋅[S] V=500×2.55+2.5V =
\frac{500 \times 2.5}{5 + 2.5}V=5+2.5500×2.5 V=12507.5=166.7 µmol/minV = \frac{1250}{7.5} =
166.7 \text{ µmol/min}V=7.51250=166.7 µmol/min
2. ATP Production
Question:
How many ATP molecules are generated from the complete oxidation of one molecule of
glucose under aerobic conditions?
Solution:
The breakdown is as follows:
Glycolysis: 2 ATP + 2 NADH (5 ATP) = 7 ATP
Pyruvate to Acetyl-CoA: 2 NADH = 5 ATP
TCA Cycle: 2 GTP + 6 NADH (15 ATP) + 2 FADH₂ (3 ATP) = 20 ATP
Total: 32 ATP (using the malate-aspartate shuttle) or 30 ATP (using the glycerol-3-phosphate
shuttle).
3. pH and Buffer Systems
,Question:
A solution contains 0.1 M acetic acid (pKa = 4.76) and 0.05 M sodium acetate. What is the pH of
the solution?
Solution:
Using the Henderson-Hasselbalch equation:
pH=pKa+log([A−][HA])pH = pKa + \log \left( \frac{[A^-]}{[HA]} \right)pH=pKa+log([HA][A−])
pH=4.76+log(0.050.1)pH = 4.76 + \log \left( \frac{0.05}{0.1} \right)pH=4.76+log(0.10.05)
pH=4.76+log(0.5)=4.76−0.30=4.46pH = 4.76 + \log (0.5) = 4.76 - 0.30 =
4.46pH=4.76+log(0.5)=4.76−0.30=4.46
4. Hemoglobin vs. Myoglobin
Question:
Why does hemoglobin exhibit a sigmoidal oxygen dissociation curve while myoglobin has a
hyperbolic curve?
Solution:
Hemoglobin undergoes cooperative binding, meaning oxygen binding at one site increases the
affinity for oxygen at other sites, producing a sigmoidal curve. Myoglobin, which stores oxygen
in muscles, binds oxygen non-cooperatively, resulting in a hyperbolic curve.
5. Lipid Metabolism
Question:
How many ATP molecules are generated from the complete oxidation of one molecule of
palmitic acid (C₁₆H₃₂O₂)?
Solution:
Beta-oxidation produces 8 acetyl-CoA, 7 NADH, and 7 FADH₂
TCA cycle (from 8 acetyl-CoA) produces 24 NADH, 8 FADH₂, and 8 GTP
ATP Calculation:
NADH: (24 + 7) × 2.5 = 77.5 ATP
FADH₂: (8 + 7) × 1.5 = 22.5 ATP
GTP: 8 × 1 = 8 ATP
, Total ATP: 108 ATP – 2 ATP (activation) = 106 ATP
6. DNA Replication
Question:
What enzyme is responsible for unwinding the DNA helix during replication?
Solution:
Helicase is responsible for unwinding the DNA double helix to allow replication to proceed.
7. Metabolic Disorders
Question:
A patient has a deficiency in glucose-6-phosphatase. What metabolic disorder does this
indicate, and what are the symptoms?
Solution:
This indicates Von Gierke's Disease (Glycogen Storage Disease Type I). Symptoms include:
Severe hypoglycemia
Hepatomegaly (enlarged liver)
Lactic acidosis
Hyperlipidemia
8. Amino Acid Catabolism
Question:
Which amino acids are exclusively ketogenic?
Solution:
Only leucine and lysine are exclusively ketogenic, meaning they can be converted into ketone
bodies but not glucose.
9. Urea Cycle
, Question:
What is the immediate nitrogen donor in the conversion of ornithine to citrulline in the urea
cycle?
Solution:
Carbamoyl phosphate donates the nitrogen group in the reaction catalyzed by ornithine
transcarbamoylase.
10. Hormonal Regulation of Metabolism
Question:
How does insulin regulate glucose metabolism in the liver?
Solution:
Insulin:
Increases glycogenesis (stimulates glycogen synthase)
Inhibits glycogenolysis and gluconeogenesis
Increases glycolysis (activates PFK-1 and pyruvate kinase)
Stimulates lipogenesis
11. Glycolysis Regulation
Question:
Which enzyme is the rate-limiting step of glycolysis, and how is it regulated?
Solution:
Phosphofructokinase-1 (PFK-1) is the rate-limiting enzyme of glycolysis.
Activated by: AMP, Fructose-2,6-bisphosphate (F-2,6-BP)
Inhibited by: ATP, citrate
12. Electron Transport Chain (ETC)
Question:
What is the role of Complex IV in the electron transport chain?
Solution:
Complex IV (Cytochrome c oxidase) transfers electrons from cytochrome c to molecular oxygen
Review UNE medical biochemistry| 290
Questions| With Complete Solutions
Course
UNE Biochemistry
1. Enzyme Kinetics
Question:
A certain enzyme follows Michaelis-Menten kinetics. If the VmaxV_{max}Vmax is 500 µmol/min
and the KmK_mKm is 5 mM, what is the reaction velocity when the substrate concentration is
2.5 mM?
Solution:
Using the Michaelis-Menten equation:
V=Vmax⋅[S]Km+[S]V = \frac{V_{max} \cdot [S]}{K_m + [S]}V=Km+[S]Vmax⋅[S] V=500×2.55+2.5V =
\frac{500 \times 2.5}{5 + 2.5}V=5+2.5500×2.5 V=12507.5=166.7 µmol/minV = \frac{1250}{7.5} =
166.7 \text{ µmol/min}V=7.51250=166.7 µmol/min
2. ATP Production
Question:
How many ATP molecules are generated from the complete oxidation of one molecule of
glucose under aerobic conditions?
Solution:
The breakdown is as follows:
Glycolysis: 2 ATP + 2 NADH (5 ATP) = 7 ATP
Pyruvate to Acetyl-CoA: 2 NADH = 5 ATP
TCA Cycle: 2 GTP + 6 NADH (15 ATP) + 2 FADH₂ (3 ATP) = 20 ATP
Total: 32 ATP (using the malate-aspartate shuttle) or 30 ATP (using the glycerol-3-phosphate
shuttle).
3. pH and Buffer Systems
,Question:
A solution contains 0.1 M acetic acid (pKa = 4.76) and 0.05 M sodium acetate. What is the pH of
the solution?
Solution:
Using the Henderson-Hasselbalch equation:
pH=pKa+log([A−][HA])pH = pKa + \log \left( \frac{[A^-]}{[HA]} \right)pH=pKa+log([HA][A−])
pH=4.76+log(0.050.1)pH = 4.76 + \log \left( \frac{0.05}{0.1} \right)pH=4.76+log(0.10.05)
pH=4.76+log(0.5)=4.76−0.30=4.46pH = 4.76 + \log (0.5) = 4.76 - 0.30 =
4.46pH=4.76+log(0.5)=4.76−0.30=4.46
4. Hemoglobin vs. Myoglobin
Question:
Why does hemoglobin exhibit a sigmoidal oxygen dissociation curve while myoglobin has a
hyperbolic curve?
Solution:
Hemoglobin undergoes cooperative binding, meaning oxygen binding at one site increases the
affinity for oxygen at other sites, producing a sigmoidal curve. Myoglobin, which stores oxygen
in muscles, binds oxygen non-cooperatively, resulting in a hyperbolic curve.
5. Lipid Metabolism
Question:
How many ATP molecules are generated from the complete oxidation of one molecule of
palmitic acid (C₁₆H₃₂O₂)?
Solution:
Beta-oxidation produces 8 acetyl-CoA, 7 NADH, and 7 FADH₂
TCA cycle (from 8 acetyl-CoA) produces 24 NADH, 8 FADH₂, and 8 GTP
ATP Calculation:
NADH: (24 + 7) × 2.5 = 77.5 ATP
FADH₂: (8 + 7) × 1.5 = 22.5 ATP
GTP: 8 × 1 = 8 ATP
, Total ATP: 108 ATP – 2 ATP (activation) = 106 ATP
6. DNA Replication
Question:
What enzyme is responsible for unwinding the DNA helix during replication?
Solution:
Helicase is responsible for unwinding the DNA double helix to allow replication to proceed.
7. Metabolic Disorders
Question:
A patient has a deficiency in glucose-6-phosphatase. What metabolic disorder does this
indicate, and what are the symptoms?
Solution:
This indicates Von Gierke's Disease (Glycogen Storage Disease Type I). Symptoms include:
Severe hypoglycemia
Hepatomegaly (enlarged liver)
Lactic acidosis
Hyperlipidemia
8. Amino Acid Catabolism
Question:
Which amino acids are exclusively ketogenic?
Solution:
Only leucine and lysine are exclusively ketogenic, meaning they can be converted into ketone
bodies but not glucose.
9. Urea Cycle
, Question:
What is the immediate nitrogen donor in the conversion of ornithine to citrulline in the urea
cycle?
Solution:
Carbamoyl phosphate donates the nitrogen group in the reaction catalyzed by ornithine
transcarbamoylase.
10. Hormonal Regulation of Metabolism
Question:
How does insulin regulate glucose metabolism in the liver?
Solution:
Insulin:
Increases glycogenesis (stimulates glycogen synthase)
Inhibits glycogenolysis and gluconeogenesis
Increases glycolysis (activates PFK-1 and pyruvate kinase)
Stimulates lipogenesis
11. Glycolysis Regulation
Question:
Which enzyme is the rate-limiting step of glycolysis, and how is it regulated?
Solution:
Phosphofructokinase-1 (PFK-1) is the rate-limiting enzyme of glycolysis.
Activated by: AMP, Fructose-2,6-bisphosphate (F-2,6-BP)
Inhibited by: ATP, citrate
12. Electron Transport Chain (ETC)
Question:
What is the role of Complex IV in the electron transport chain?
Solution:
Complex IV (Cytochrome c oxidase) transfers electrons from cytochrome c to molecular oxygen
