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EXAMINATION OCTOBER 2024
(SUPPLEMENTARY EXAM)
FIRST MBBS
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BIO-CHEMISTRY (PAPER - II) (NEW) - LEVEL 3[Time: As Per Schedule]
[Max. Marks: 100]
Instructions:
Seat No:
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1. Fill up strictly the following details on your answer booka. Name of the Examination : FIRST MBBS
b. Name of the Subject : BIO-CHEMISTRY (PAPER - II) (NEW) -
LEVEL 3
c. Subject Code No : 2406000101030702
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2. Sketch neat and labelled diagram wherever necessary.3. Figures to the right indicate full marks of the question.
4. All questions are compulsory.
Student's Signature
Section A
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Q.1 Multiple choice questions (20 out of 20)20x1=20
1. The base sequence of the strand of DNA used as the template for
transcription is GATCTAC. What is the base sequence of the RNA
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product? (All sequences are written 5' 3' according to standardconvention.)
a) CTAGATG
b) GTAGATC
c) GAUCUAC
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d) CUAGAUG2. A 6-month-old infant is seen in the emergency room with a fractured rib
and subdural hematoma. The child's hair is thin, colourless, and tangled.
His serum copper level is decreased. Developmental delay is prominent.
Which enzyme activity requires copper as co- factor?
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a) Lysyl oxidaseb) Prolyl hydroxylase
c) -Glutamyl carboxylase
d) -1,4-glucosidase
3. All are iron containing enzymes, EXCEPT
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a) Cytochrome oxidaseb) Peroxidase
c) Tyrosinase
d) Catalase
4. A 36 years old male was diagnosed with pulmonary TB. He was
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receiving Isoniazid for the treatment. He started developing numbnessof hands and legs. What should be given to the patient?
a) Vitamin B 12
b) Niacin
c) Pyridoxine
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d) Biotin2406000101030702
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5. A 67-year-old man presented to the emergency department with a 1
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week history of angina and shortness of breath. He complained that hisface and extremities had a "blue colour." His medical history included
chronic stable angina treated with isosorbide dinitrate and nitro-
glycerine. Blood obtained for analysis was chocolate-coloured. Which
one of the following is the most likely diagnosis?
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a) Sickle cell anemiab) Carboxy hemoglobinemia
c) Met-hemoglobinemia
d) -Thalassemia
6. Fluidity of cell membrane is increased by
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a) Polyunsaturated fatty acidsb) Cholesterol at temperature above the Tm
c) Trans fatty acids
d) Long chain saturated fatty acids
7. Which one of the following statements is true about proteolytic
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enzymes?a) Trypsin is activated by HCI.
b) Pepsin acts on peptide bonds formed by carboxyl groups of acidic
amino acids.
c) Chymotrypsin acts on peptide bonds formed by carboxyl groups of
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hydrophilic amino acids.d) Trypsin acts on peptide bonds formed by carboxyl groups of basic
amino acids.
8. Which one of the following is the toxin-based vaccine?
a) Polio
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b) Diphtheriac) MMR
d) Rabies
9. All the following amino acids are used for the synthesis of purine
nucleotides, EXCEPT
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a) Glycineb) Alanine
c) Aspartate
d) Glutamine
10. The immunoglobulin which is also called Cytophilic antibody is
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a) IgGb) IgD
c) IgM
d) IgE
11. Human serum albumin, the most abundant blood protein, has multiple
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roles, including acting as a buffer to help maintain blood pH. Albumincan act as a buffer because of which one of the following?
a) The amino and carboxyl ends of albumin can donate and accept
protons in the range of physiologic pH.
b) The protein contains many histidine residues containing side chain
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with pKa value near to the physiological pH.c) Albumin contains peptide bonds that readily hydrolyze, consuming
hydrogen and hydroxyl ions.
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d) Albumin contains a large number of hydrogen bonds in a-helices,
which can accept and donate protons.
12. A 53-year-old man, who has been smoking for the past 35 years at a
two-pack-a-day rate, visits his physician for a cough that will not go
away, and for difficulty in breathing. A chest X-ray rules out cancer, but
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does display "air trapping.". At the molecular level, this disease is dueto which one of the following?
a) Enhanced trypsin activity in the lung
b) Enhanced reduction of sulfhydryl groups in the lung
c) Decreased al-antitrypsin activity in the lung
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d) Decreased trypsin activity in the lung13. A 72 years old man diagnosed with Alzheimer's disease. In this patient
Amyloid precursor protein's normal alpha helical structure gets
disrupted due to mutation. The following mutational change affects
alpha helical structure of mutant protein.
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a) Methionine to Prolineb) Valine to Alanine
c) Glutamate to Aspartate
d) Lysine to Arginine
14. A bacterial mutant grows normally at 32?C but at 42?C accumulates
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short segments of newly synthesized DNA. Which one of the followingenzymes is most likely to be defective at the higher temperature in this
mutant?
a) DNA primase
b) DNA ligase.
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c) DNA polymerased) DNA helicase
15. A pathologist, while doing an autopsy of a patient who died from
Creutzfeldt-Jakob syndrome, accidentally cut himself while examining
the brain. The pathologist became very concerned for his well-being.
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The precipitating event in the patient's brain that led to this disease iswhich one of the following?
a) Infection of the brain with a virus
b) Proteolytic cleavage of an existing brain protein
c) An altered secondary and tertiary structures for an existing brain
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proteind) Altered gene expression
16. A medical student has been exposed to a patient with tuberculosis and
developed a positive tuberculin test (PPD), but exhibited a normal chest
X-ray. He is placed on a 6-month course of prophylactic treatment of
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isoniazid, but subsequently develops peripheral neuropathies. Which ofthe following vitamins would be considered a treatment for the
neurotoxicity?
a) Niacin
b) Cobalamin
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c) Folic acidd) Pyridoxine
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17. A 45-year-old male is concerned about his risk of a heart attack since
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his brother just had a heart attack at the age of 46. His physician ordersan HbA1C, lipid panel, and homocysteine level. A high homocysteine
level could be associated with a deficiency of which one of the
following vitamins?
a) Pyridoxine
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b) Riboflavinc) Niacin
d) Ascorbic acid
18. Identify the incorrect statement about Ion exchange chromatography
a) Carboxylic & sulphonic acid are bound to a stationary phase for
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cation exchange.b) Anion-exchange solid phases have quaternary amines.
c) Solutes are eluted with a solution containing sodium for anion
exchange.
d) Can be used for analyses hemoglobin.
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19. Leukemia patients are often given the compound Folinic acid (N5-formyl THF) following treatment with the drug methotrexate. Why is
Folinic acid useful as part of this treatment protocol?
a) It facilitates the uptake of methotrexate by cells
b) It can be converted to THF by bypassing folate reductase reaction
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c) It acts as an activator of thymidylate synthased) It stimulates cells of the immune system
20. A vaginal swab was collected from a rape victim. The sample was
processed and check for presence of sperm cells. Confirmation of actual
culprit can be done by matching his DNA with the DNA of sperm cells
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found in the sample. This technique is based ona) Constant number of tandem repeats
b) Long interspersed nuclear element
c) Single nucleotide polymorphism
d) Variable number of tandem repeats
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Section B
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Q.2 Long Answer Questions. (2 out of 3)
2x10=20
1. Describe phenylalanine and tyrosine metabolism (4). Describe
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various products (only steps) formed from tyrosine (3). Write defect,clinical features, and treatment of phenylketonuria (3).
2. Describe the characteristics of genetic code (2). Describe the
translation process in eukaryotes (6). Explain the role of chaperones
in protein folding (2)
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3. Describe formation, uptake, conjugation, and excretion of bilirubin(4). Describe pre-hepatic. hepatic and post-hepatic jaundice with
differential diagnosis (6).
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Q.3 Short Answer Questions (10 out of 11)
10x2=20
1. Write at least four biologically active nucleotides with their
functions.
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2. Edema develops when the albumin level is decreased. Why?3. Explain why ammonia is toxic to our body.
4. Write at least two products formed from glycine with their
significance.
5. Write the biological and clinical significance of the transamination
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reaction.6. What is a folate trap? Explain by drawing reactions.
7. How does vitamin D activate in our body?
8. Explain why barbiturates precipitate an attack of porphyria and why
administration of glucose alleviates symptoms of porphyria.
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9. Write the principle of electrophoresis. Draw a normalelectrophoretogram of plasma proteins.
10. Write at least six secondary causes of hyperuricemia. Why
allopurinol is given in the treatment of gout?
11. Describe eukaryotic DNA polymerases and their functions.
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Section C
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Q.4 Short Answer Questions (4 out of 5)4x5=20
1. Describe any five factors that affect enzyme activity.
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2. Describe steps and clinical applications of DNA recombinanttechnology (3+2)
3. Describe the structure and functions of immunoglobulins.
4. Enumerate cardiac biomarkers in the order of their earliest rise in
myocardial infarction. What is a flipped pattern? Describe cardiac
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biomarkers that are not enzymes. (1+1+3)5. Describe the second messenger system.
Q.5 Clinical Cases (2 out of 2)
2x10=20
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1. A 4-year-old child had loose, hypermobile joints, and soft, hyperflexibleskin. His fingers could be extended to such an extent that they touched
the back of his hand. The skin was easily iron or scarred. In addition, he
had scoliosis (bent spine). A sample of collagen tissue was obtained by
biopsy from two sources: skin and cartilage. The skin collagen was
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deficient in hydroxylysyl residues, whereas the collagen obtained fromcartilage had a normal content of these residues. The patient did not have
any features that were suggestive of vascular collagen involvement.
1. What is the biochemical defect in this case? Explain (2)
2. Write amino acid sequence in collagen. What is a 'quartered staggered
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arrangement'? (2)3. How does collagen get mature? (2)
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4. How does cross-linking form in collagen structure? (2)
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5. Write four collagen disorders caused by mutation. (2)2. A 15-year-old Indian aboriginal girl presents to the emergency room
with complaints of bilateral thigh and hip pain. The pain has been present
for 1 day and is steadily increasing in severity. Acetaminophen and
ibuprofen have not relieved her symptoms. She denies any recent trauma
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or excessive exercise. She reported fatigue and a burning sensationduring urination. She reports having similar pain episodes in the past,
sometimes requiring hospitalization. On examination, she is afebrile. Her
conjunctiva and mucosal membranes are slightly pale in color. She has
nonspecific bilateral anterior thigh pain with no abnormalities
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appreciated. The remainder of her examination is completely normal. Herwhite blood cell count is elevated at 17,000/mm3, and her hemoglobin
(Hb) level is decreased to 7.1 g/dL. Peripheral blood smear showed sickle
cells. The urinalysis demonstrated an abnormal number of numerous
bacteria.
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1. Explain the mechanism of polymerization that takes place inside theRBCs of this patient. (3)
2. Why Oxygen dissociation curve of Hb is sigmoid in shape? (2)
3. Why does sickling occur only under a deoxygenated state? (1)
4. How Hb electrophoresis helps to differentiate sickle cell disease and
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trait patients? (2)5. Explain the basis behind pain crisis in this patient. (2)
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