आधारभूत विज्ञान (Anatomy, Physiology, Biochemistry) – Basic Sciences MCQ
आधारभूत विज्ञान (Anatomy, Physiology, Biochemistry) – MD/MS प्रवेश
Basic Sciences · MECEE-PG – MD/MS/MDS Entrance · ४३३ प्रश्न
४३३ प्रश्न उपलब्ध। मोड छान्नुहोस्:
आधारभूत विज्ञान (Anatomy, Physiology, Biochemistry): प्रश्न र उत्तर
सही लागेको विकल्पमा थिच्नुहोस्। सही भए हरियो, गलत भए रातो देखिन्छ; ३ सेकेन्डपछि सही उत्तर र व्याख्या देखिन्छ।
सही: ० / ०
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A competitive inhibitor of an enzyme causes:
सही उत्तर: क) Increased apparent Km with unchanged Vmax
A competitive inhibitor competes for the active site, so more substrate is needed for half-maximal velocity (higher Km), but very high substrate overcomes it (Vmax unchanged). Non-competitive inhibitors lower Vmax without changing Km.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Cyanide poisoning blocks the electron transport chain by inhibiting:
सही उत्तर: क) Complex IV (cytochrome c oxidase)
Cyanide binds the ferric iron of cytochrome a3 in complex IV, stopping oxygen use despite adequate oxygen delivery; carbon monoxide also inhibits complex IV. Oligomycin inhibits complex V and rotenone inhibits complex I.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The enzyme catalysing the rate-limiting step of the hexose monophosphate (pentose phosphate) shunt is:
सही उत्तर: क) Glucose-6-phosphate dehydrogenase
G6PD produces NADPH, which keeps glutathione reduced and protects RBCs from oxidative damage; its deficiency causes haemolysis after oxidant drugs or fava beans. Transketolase, a thiamine-dependent enzyme, acts in the non-oxidative phase.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Lesch–Nyhan syndrome results from deficiency of:
सही उत्तर: ग) Hypoxanthine-guanine phosphoribosyltransferase (HGPRT)
HGPRT deficiency blocks the purine salvage pathway, causing hyperuricaemia, gout, intellectual disability and self-mutilation; it is X-linked recessive. Adenosine deaminase deficiency causes severe combined immunodeficiency.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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McArdle disease (glycogen storage disease type V) is caused by deficiency of:
सही उत्तर: ग) Muscle glycogen phosphorylase
Lack of muscle glycogen phosphorylase causes exercise intolerance, cramps and myoglobinuria with no rise in blood lactate after ischaemic exercise. Liver phosphorylase deficiency is Hers disease (type VI).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Von Gierke disease (glycogen storage disease type I) is due to deficiency of:
सही उत्तर: ग) Glucose-6-phosphatase
Without glucose-6-phosphatase the liver cannot release free glucose, causing severe fasting hypoglycaemia, lactic acidosis, hyperuricaemia and hepatomegaly. Acid alpha-glucosidase deficiency is Pompe disease (type II).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Urine that darkens on standing and ochronosis are features of a deficiency of:
सही उत्तर: घ) Homogentisate oxidase
In alkaptonuria, homogentisic acid accumulates and oxidises to a black pigment that darkens urine and deposits in connective tissue (ochronosis), causing arthritis. Branched-chain keto acid dehydrogenase deficiency causes maple syrup urine disease.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Classical phenylketonuria is caused by deficiency of:
सही उत्तर: ग) Phenylalanine hydroxylase
Phenylalanine hydroxylase converts phenylalanine to tyrosine; its deficiency leads to accumulation of phenylalanine, intellectual disability and a musty odour. Tyrosine becomes an essential amino acid in PKU.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The rate-limiting enzyme of heme synthesis is:
सही उत्तर: क) ALA synthase
Delta-aminolevulinic acid synthase, which needs pyridoxal phosphate, catalyses the first and rate-limiting step and is feedback-inhibited by heme. ALA dehydratase and ferrochelatase are the enzymes inhibited by lead.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The rate-limiting enzyme of the urea cycle is:
सही उत्तर: ग) Carbamoyl phosphate synthetase I
Mitochondrial carbamoyl phosphate synthetase I is rate-limiting and requires N-acetylglutamate as an allosteric activator. Ornithine transcarbamoylase deficiency is, however, the most common inherited urea cycle disorder.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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