Q1. A mutation replaces a polar amino acid with a nonpolar one in the hydrophobic core of a globular protein. What is the most likely consequence?
A) Increased solubility
B) Loss of tertiary structure stability
C) Enhanced enzymatic activity
D) Change in primary structure only
E) No effect on folding
Q2. Which level of protein structure is directly stabilized primarily by hydrogen bonds between backbone amide and carbonyl groups?
A) Primary
B) Secondary
C) Tertiary
D) Quaternary
E) All of the above
Q3. A patient presents with sickle cell disease. The molecular defect involves:
A) Loss of an entire β-globin gene
B) Substitution of glutamic acid by valine at position 6 of the β-chain
C) Deletion of three nucleotides in the α-globin gene
D) Premature stop codon in β-globin
E) Excess glycosylation of hemoglobin
Q4. (True/False) The peptide bond has partial double bond character due to resonance.
Q5. Which amino acid side chain is most likely to be found in the active site of a hydrolytic enzyme acting on ester bonds?
A) Valine
B) Serine
C) Phenylalanine
D) Isoleucine
E) Alanine
Q6. Denaturation of an enzyme:
A) Always breaks covalent peptide bonds
B) Only affects quaternary structure
C) Can be caused by changes in pH or temperature
D) Is irreversible under any condition
E) Increases substrate affinity
Le vrai défi est l'accès. Les QCM de base pullulent sur les sites de partage (Studyrama, Kartable), mais les QCM Biochimie 1ere annee medecine exclusive sont souvent derrière des paywalls ou des groupes privés de tutorat.
Critères de qualité pour reconnaître une ressource vraiment exclusive : qcm biochimie 1ere annee medecine exclusive
Conseil d'initié : Rejoignez les tutorats "Premium" des grandes facultés (Paris Descartes, Lyon Est, Marseille). Ils distribuent souvent des fascicules de 500 QCM exclusifs qui ne sont pas diffusés en ligne.
Pour tirer profit de ces QCM, ne les faites pas passivement. Voici la méthode en 3 phases :
Phase 1 – Le décorticage (J1)
Phase 2 – L’étude inversée (J2)
Phase 3 – La restructuration (J3)
Q25. A patient presents with hypoglycemia, hepatomegaly, and muscle weakness. Fasting plasma free fatty acids and ketones are low. This suggests a defect in:
A) Carnitine shuttle
B) HMG-CoA lyase
C) Lipoprotein lipase
D) Acyl-CoA dehydrogenase
E) Acetyl-CoA carboxylase
Q26. Which lipoprotein is most elevated in familial hypercholesterolemia (defective LDL receptor)?
A) Chylomicrons
B) VLDL
C) IDL
D) LDL
E) HDL Le vrai défi est l'accès
Q27. During prolonged fasting, the liver produces ketone bodies from:
A) Glucose
B) Acetyl-CoA derived from β-oxidation
C) Lactate
D) Amino acids only
E) Glycerol
Q28. (True/False) Acetyl-CoA carboxylase is activated by palmitoyl-CoA.
Q29. Statins lower cholesterol by inhibiting:
A) HMG-CoA synthase
B) HMG-CoA reductase
C) Acyl-CoA cholesterol acyltransferase (ACAT)
D) Cholesterol ester transfer protein (CETP)
E) LDL oxidation
Q30. The rate-limiting step in fatty acid synthesis is catalyzed by:
A) Fatty acid synthase
B) Acetyl-CoA carboxylase
C) Carnitine palmitoyltransferase I
D) Malonyl-CoA decarboxylase
E) Thiolase
Question: concerning the Michaelis-Menten equation $V = \fracV_max[S]K_m + [S]$: A. $K_m$ is the substrate concentration required to reach $\fracV_max2$. B. $K_m$ is a constant independent of enzyme concentration. C. When $[S] >> K_m$, the reaction velocity is zero-order regarding the substrate. D. A low $K_m$ indicates a low affinity of the enzyme for the substrate. E. Lineweaver-Burk representation (double reciprocal plot) allows for the graphical determination of $K_m$ and $V_max$.
Answer Key:
Ne révisez pas sur des pavés de texte. 6-bisphosphate D) Glucose-6-phosphate E) Acetyl-CoA
Q19. During fasting, which enzyme is activated in the liver to maintain blood glucose?
A) Glucokinase
B) Glucose-6-phosphatase
C) Hexokinase
D) Pyruvate kinase
E) Glycogen synthase
Q20. A deficiency in glucose-6-phosphate dehydrogenase (G6PD) leads to:
A) Hypoglycemia
B) Hemolytic anemia upon oxidative stress
C) Lactate acidosis
D) Galactosemia
E) Glycogen storage disease type I
Q21. Which hormone promotes glycogenesis in the liver?
A) Glucagon
B) Cortisol
C) Epinephrine
D) Insulin
E) Thyroid hormone
Q22. (True/False) Gluconeogenesis uses pyruvate carboxylase and PEP carboxykinase to bypass the irreversible step of pyruvate kinase.
Q23. The Cori cycle involves:
A) Conversion of lactate to glucose in the liver
B) Direct conversion of alanine to glucose in muscle
C) Fatty acid synthesis from glucose in adipose tissue
D) Ketogenesis during starvation
E) Urea cycle integration with TCA cycle
Q24. Which of the following is a key allosteric activator of glycolysis?
A) ATP
B) Citrate
C) Fructose-2,6-bisphosphate
D) Glucose-6-phosphate
E) Acetyl-CoA