Q1. Which of the following substrates links urea cycle to Kreb’s cycle?
A. Fumarate
B. Oxaloacetate
C. Ornithine
D. Citrullin
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Ans: A. Fumarate
Arginosuccinate an intermediate of urea cycle is cleaved by argininosuccinate lyase to arginine and fumarate. This fumarate formed in the urea cycle can be funnelled into TCA cycle to be converted to malate and then to oxaloacetate.
Oxaloacetate formed in the krebs cycle can be transaminated to aspartate which is an intermediate of urea cycle.
Reference: Textbook of Biochemistry By D M Vasudevan, 3rd Edition, Page 161
Q2. Sources of the nitrogen in urea cycle are the following:
A. Aspartate and ammonia
B. Glutamate and ammonia
C. Arginine and ammonia
D. Uric acid
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Ans: A. Aspartate and ammonia
The 2 nitrogen atoms of urea are derived from two sources, one from ammonia and other from alpha amino group of aspartic acid.
Reference: Textbook of Biochemistry By DM Vasudevan, 3rd Edition, Pages 163-5
Q3. Which of the following is the key enzyme which regulates urea cycle?
A. Carbamoyl phosphate synthase
B. Ornithine transcarbamoylase
C. Argininosuccinate synthase
D. Arginosuccinase
Q1. Which of the following is true regarding Pemphigus vulgaris?
A. Protozoa
B. STD
C. Virus
D. Autoimmune
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Ans: D. Autoimmune
Pemphigus vulgaris (PV) is an autoimmune, mucocutaneous, blistering disease characterized by an intraepidermal split that results in superficial flaccid bullae.
Pemphigus vulgaris (PV) is a mucocutaneous blistering disease that predominates in patients >40 years. PV typically begins on mucosal surfaces and often progresses to involve the skin. PV is characterized by fragile, flaccid blisters that rupture to produce extensive denudation of mucous membranes and skin.
Reference: Chapter 107. Dermatologic Conditions. In: Hall JB, Schmidt GA, Wood LH. eds. Principles of Critical Care, 3e; Chapter 54. Immunologically Mediated Skin Diseases. In: Longo DL, Fauci AS, Kasper DL, Hauser SL, Jameson J, Loscalzo J. eds. Harrison’s Principles of Internal Medicine, 18e.
Q2. A female presented with a skin lesions all over the body which shows positive ‘bulla spread sign’. It is characteristic of:
A. Herpes gestationis
B. Bullous pemphigoid
C. Pemphigus vulgaris
D. Herpes simplex
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Ans: C. Pemphigus vulgaris
Pemphigus vulgaris is characterized by cutaneous and mucosal blisters. On application of tangential pressure on normal skin results in formation of new bulla (Nikolsky sign) or if applied to pre-existing bulla results in the spread of bulla (bulla spread sign). Cutaneous lesions predominantly present on face, trunk, axillae, groins, and scalp.
Reference: Illustrated Synopsis Of Dermatology & Sexually Transmitted Diseases By Khanna, 3rd edition, Page 64.
Q3. Tzanck preparation is used for the following skin conditions, EXCEPT:
A. Pemphigus
B. SSS syndrome
C. Senear Usher syndrome
D. Fungal infections