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Biochemistry USMLE practice questions correct solutions, Exams of Nursing

Cheyney University of PennsylvaniaNursing

Biochemistry USMLE practice questions correct solutions

Typology: Exams

2025/2026

Available from 02/12/2026

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Biochemistry USMLE practice questions correct
solutions
1.
thrombocytopenia:
deficiency of platelets in the blood. This causes bleeding into the tissues,
bruising, and
slow blood clotting after injury.
2.
A 16 year old boy presented to a doctor by his mother for the
injury which
he had recently during cycle riding. On examination
doctor noticed the loose, overly-flexible joints, smooth or stretchy,
easily-bruised skin and abnormal wound healing and scar formation.
This is the characteristic feature of the
disorder known as: Ehlers-Danlos
syndrome
3. A 67-year-old man has a restricted diet that includes no fresh citrus
fruits
or leafy green vegetables. His teeth are loose and his gums bleed
easily. This patient's disorder most likely results from a defect in
collagen synthesis that
involves which of the following amino acids?:
Hydroxyproline
pf3
pf4
pf5
pf8
pf9
pfa
pfd
pfe
pff
pf12
pf13
pf14
pf15
pf16
pf17
pf18
pf19
pf1a
pf1b
pf1c
pf1d
pf1e
pf1f
pf20
pf21
pf22
pf23
pf24
pf25
pf26
pf27
pf28
pf29
pf2a
pf2b
pf2c
pf2d
pf2e
pf2f
pf30
pf31
pf32
pf33

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1 / 51

Biochemistry USMLE practice questions correct

solutions

  1. thrombocytopenia: deficiency of platelets in the blood. This causes bleeding into the tissues, bruising, and slow blood clotting after injury.
  2. A 16 year old boy presented to a doctor by his mother for the injury which he had recently during cycle riding. On examination doctor noticed the loose, overly-flexible joints, smooth or stretchy, easily-bruised skin and abnormal wound healing and scar formation. This is the characteristic feature of the disorder known as: Ehlers-Danlos syndrome
  3. A 67-year-old man has a restricted diet that includes no fresh citrus fruits or leafy green vegetables. His teeth are loose and his gums bleed easily. This patient's disorder most likely results from a defect in collagen synthesis that involves which of the following amino acids?: Hydroxyproline

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  1. N-terminal and C -terminal polypeptides of collagen are cleaved in: Extracellular space
  2. A 15 year old boy visited the physician with the complaints of joint pain, bleeding of the gums and loosening of the teeth. This is due to the defect in the post translational modification of collagen molecule. This problem is corrected by supplying which compound in the diet of the patient?: Ascorbic acid
  3. A 40 year old woman, cigarette smoker, complained about shortness of breath and chronic fatigue. Which one of the following most likely explains the patient's pulmonary symptoms?: Deficiency of α1- Antitrypsin
  4. Cross-linking of collagen to form mature collagen fibrils occurs at which of the following sites?: Extracellular space
  5. Individuals who are habitual and chronic smokers are likely to have a func- tional deficiency of alpha 1 antitrypsin. This can cause pulmonary emphysema based on accelerated degradation of: Elastin
  6. Some forms of Ehlers-Danlos syndrome are characterized by abnormally elastic skin. This is due to defective formation and

4 / 51 inhibitor of the enzyme acetylcholinesterase, an important mediator of neurotransmit- ter action. Which of the following best describes the effect of this poison on the enzyme?: Vmax is reduced, Km is unaltered (Non competitive inhibitor)

  1. The conversion of dihydroxyacetone (DHAP) to glyceraldehyde- 3-phosphate (GAP) is a freely reversible reaction with an equilibrium constant close to 1. The interconversion is catalyzed by the enzyme triose phosphate isomerase. The presence of this enzyme in a solution of glyceraldehyde-3-phosphate will have the following effect compared with an identical solution with no enzyme.: De- crease the time taken to reach equilibrium.
  2. Which of the following statement is true of thrombin?: It stimulates platelets aggrega- tion
  3. The number of substrate molecules converted to product by one molecule of enzyme each second is known as the: turnover number
  4. Allosteric postive homo-tropic effector:
  5. Psoriasis is a chronic, non-contagious autoimmune disease

5 / 51 that affects the skin and joints. It commonly causes red, scaly patches to appear on the skin. Which forms of retinoids is useful in the treatment of this condition?: Ratinoic acid

  1. Riboflavin plays a key role in energy metabolism and is required for the metabolism of fats, carbohydrates and proteins. Deficiency features of the vitamin includes cracked and red lips, inflammation of the lining of mouth and tongue, mouth ulcers, cracks at the corners of the mouth. In which one of the following reactions its coenzyme is required?: Acyl CoA > 2- trans- Enoyl CoA
  2. 20 year old medical student met an accident and suffered from multiple injuries all over the body with the bone fracture. Your surgeon colleague prefers to supplement patients with ascorbic acid after surgery. The doctor trying to optimize which one of the following process?: The hydroxylation of proline in tropocollagen=helps with the healing of the bone fracture.
  3. A 16 month-old girl of middle eastern parents is admitted with growth retar- dation. Her long bones show demineralization with bowing of both the arms and the legs. The patient avoided dairy

7 / 51 alcohol abuse. His symptoms are typically associated with the dietary deficiency or impaired absorption of which of the following vitamins?: Vitamin B1 =fixes neurodegenerative problems, and eye sights.

  1. Your patient has been diagnosed with pernicious anemia. Since part of this syndrome involves megaloblastic anemia with neuropsychiatric problems (myelopathy). You decide to treat the patient with folate supplements. Which of the following do you expect to happen?: Folate will successfully treat the megaloblastic anemia, but not the myelopathy.
  2. position of equilibrium in the graph:
  3. A particular cytochrome enzyme normally has oxidoeductase activity and contains an iron-based heme group. The enzyme is translated and folded before the heme group is incorporated. An individual who has an iron mal- absorption problem will produce only the protein without the heme. Such a protein is referred to as a(n): apoenzyme
  4. A 40 year old woman primarily subsists on fast foods, hotdogs

8 / 51 and diet drinks. Primary examination reveals bleeding gums, loosening of the teeth and perifollicular hemorrhages. The mechanism of vascular instability in this patient is most closely associated with deficiency of which of the following vitamins?: Vitamin C

  1. A 38 year old man with 8 year history of alcohol abuse present to a family doctor with a complaint of diminished taste and smell. Physical examination reveals rash across his face and neck. In addition poor healing of skin incision site on the back of his right hand. Which of the trace element is most likely deficient?: Zink
  2. A 30year old man who is being treated with isoniazid for pulmonary tuber- culosis develops microcytic anemia. Laboratory studies shows increase serum ferritin. And iron. A bone marrow examination showes increased iron stores. Which of the following vitamin deficiency is most likely responsible for the anemia: Pyridoxine
  3. Examination of the blood of an alcoholic revealed

10 / 51 Fenoxycarb is a non-competitive inhibitor of the enzyme acetylcholinesterase, an important mediator of neurotransmitter action. Which of the following statements about the Lineweaver- Burk plots for the inhibited (+I) and uninhibited (-I) enzyme reaction is correct?: The plots will intersect on the X-axis

  1. A 75-year-old woman is seen in the emergency room with a fractured arm. Physical examination revealed multiple bruises and perifollicular hem- orrhages, periodontitis, and painful gums. Her diet consists predominately of weak coffee, bouillon, rolls, and plain pasta. Lab results indicated mild microcytic anemia. Which of the following enzymes should be less active than normal in this patient?: Prolyl hydroxylase-the enzyme that is less active in this patient leading to her painful gums, bruises and etc.
  2. Retinitis pigmentosa (RP) is a genetically heterogeneous disease charac- terized by progressive photoreceptor degeneration and ultimately blindness. Mutations in more than 20 different genes have been identified in clinically affected patients. One might expect this gene to encode a polypeptide required for the activity of a: cGMP phosphodiesterase

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  1. Source of ascorbic acid is glucose. It can not be synthesized in humans due to the absence of the enzyme: L-gulonolactone oxidase
  2. Which of the following statement to different types of anemia is true?: Iron deficiency is characterized by hypochromic microcytic anemia
  3. ich of the following is an example of a second messenger?: cAMP
  4. The liver converts lactate from anaerobic exercise into glucose: example of anabolic process
  5. Which of the following statements is true about Janus Kinase 2 ( JAK2) re- ceptors? The ligand-binding signal is transduced through JAK2 by: phosphorylating downstream proteins
  6. In GTP dependent regulatory proteins (G proteins) the effect of the active, dissociated G-α unit is short-lived because it has its own: GTP-ase activity
  7. Biotin is involved in which type of the reactions?: carboxylation
  8. Which factor influences most to elevate plasma calcium level?: Calcitriol
  9. Which one of the following statements

13 / 51 them:: D-glycine L-glycine: except L-lysine L-arginine

  1. reduce gastric HCL secretion) deactivates the H/K ATPase in gastric parietal cells by forming a covalent bond with the ATPase. The bond was not susceptible to acid or base catalyzed hydrolysis. The drug probly contains which functional group that would be critical for its action?: Reactive sulfhydryl group
  2. If a certain amino acid has a pk1 of 4 and a pk2 of 6, what is the pH of the zwitterion (pI): 5
  3. In a neutral polar amino acid which of the following is occuring as pH is increasing towards pk1?: Deprotonation of carbonyl group
  4. What is the isoelectric point of alanine?: pH at which the net charge is zero pH at which both the carboxyl group and amino group are ionized pH at which the amino acid exists in zwitterionic form
  5. This short peptide is used as an important cofactor and required for the integrity of rbc membranes: glutathione

14 / 51

  1. A quality shared by all peptide bonds: Single bond character: NOT Rigid and planar trans-configuration Uncharged, but polar
  2. In aqueous solution, the side chains of a non-polar amino acid will tend to cluster where?: Interior of protein
  3. How is secondary structure stabilized: Hydrogen bond
  4. During electrophoresis, the restricted hb-S protein band will move towards which relative position?: Closer to the anode than Hb-C
  5. In antiparallel beta- pleated sheets what is the relative position of the N and C terminal amino acids: N and C terminal amino acids are closest to each other
  6. A 65 yr. old banker was taken to his family doctor by his son for showing mood changes, minor memory loss, and decreased motor skills. A potential explaination for his symptoms is which of the following proteins?: Misfolded form of a normal protein
  7. Which similar property will the normal prion protein share w/ an infectious prion protein?: Primary structure
  8. A man with a mild cough goes to see the doctor. Upon

16 / 51 oxygen dissociation curve

  1. It has a hyperbolic oxygen dissociation curve: Decreased 2,3- bisphosphoglycerate
  2. A 53 year-old obese male comes to your office with complaints of dizziness and headaches. After examining his lab results, you diagnose him with dia- betes mellitus. Which one of the following factors most likely influenced your decision?: Increased Hb A1c
  3. Increase of which of the following will shift the oxygen dissociation curve to the left?: Glycogen
  4. A patient presents to your office with brownish-blue coloration of the skin and membranes and complaits of anxiety, headache, and dyspnea. He also has chocolate colored blood. Which one of the following is most likely defected in this patient?: diagnosis: methemoglobinemia oxidates fe2 to fe3 which can't bind oxygen
  5. Which of the following amino acid plays a role in collagen fibril stabilization?- : Glycine
  6. Where does the signal sequence of the nascent prepro- alpha collagen polypeptide get cleaved?: Endoplasmic Reticulum (ER)

17 / 51

  1. Which of the following amino acids are hydroxylated during collagen forma- tion?: Lysine Proline
  2. Where does the cleaving of procollagen occur?: Outside the cell
  3. A patient presents with very stretchy skin and extremely flexible joints. What is the defect in this patient?: Collagen type III
  4. A smoker of 35 years comes to your office with shortness of breath and dyspnea. Which of the following AA in the a1-antitrypsin will react with smoke and inhibit the function of a1-antitrypsin?: Methioine
  5. Which of the following tissues will be most affected in a patient with a deficiency of type III collagen?: Blood vessels
  6. Proteins as well as certain nucleotides may have enzymatic activity (T/F): T
  7. An deactivated enzyme w/out its nonprotein component is a?: Apoenzyme
  8. The gibbs free energy difference between the reactants and the products will be the same whether: the rxn has been catalyzed or not
  9. Normally the total fraction of bound substrate is very large: Michel

19 / 51 Zwitterion

  1. Certain amino acids are not part of the primary structure of proteins but are modified after translation. In scurvy, which amino acid that is normally part of collagen is not synthesized?: Hyroxyproline
  2. A newborn female has a large and distorted cranium, short and deformed limbs, and very blue scleras. Radiographs demonstrate multiple limb fractures. These results are best explained by:: incorporation of defective alpha2 chains that cause instability and degradation of the triple helix
  3. A child with tall stature, loose joints, and detached retinas is found to have a mutation in type II collagen. Which of the following amino acids is most likely to be altered in mutations that distort collagen molecules?: (mutation takes place in the structure, the structure is made of glycine -X -Y
  • (repeating chains makes the structure of the collagen)
  1. The oxygen carrier of muscle is the globular protein myoglobin. Which of the following amino acids is highly likely to be localized within the interior of the molecule?: Valine
  2. The presence of which of the following structural arrangements in a protein strongly suggests that it is a DNA-binding,

20 / 51 regulatory protein?: Zinc finger

  1. The ability of hemoglobin the serve as an effective transporter of oxygen and carbon dioxide between lungs and tissues is explained by which of the following properties?: In contrast to myoglobin, hemoglobin exhibits greater changes in secondary and tertiary structure after oxygen binding
  2. Which of the following statements correctly describes transport of O2 by hemoglobin?: The plot of percentage of O2 bound versus O pressure is sigmoidal in shape
  3. The oxygen dissociation curve of normal adult hemoglobin shown below is most effectively shifted to the right by:: Increased 2,3- BPG
  4. Which of the following mutations would produce a severe thalassemia?: - Deletion of four alpha-globin chains
  5. The substitution of glu6val on the two beta chains in sickle cell hemoglobin cause which if the following?: Increased electrophoretic mobility at pH 7.
  6. The functions of many enzymes, membrane transporters,