Q-211. Vitamin A intoxication causes injury to:
a) Cytosol
b) Mitochondria
c) Lysosomes
d) Cell membrane
Answer: Lysosomes
Explanation:
Vitamin A intoxication causes rupture of lysosomal membrane.
Hyper-vitaminosis A:
Dry and pruritis skin
Hepatomegaly
Increased intra-cranial pressure
Congenital malformation
Q-212. Vitamin excreted in urine:
a) Vitamin A
b) Vitamin D
c) Vitamin C
d) Vitamin E
Answer: Vitamin C
Explanation:
Vitamin A, D, K and E are fat soluble vitamins. They are not readily excreted in the urine and significant quantities are stored in the liver and adipose tissue.
In contrast to water soluble vitamins, only Vitamin K has a coenzyme function.
Q-213. Active form of vitamin D is
a) Ergocalciferol
b) Cholecalciferol
c) 25-hydroxycholecalciferol
d) 1, 25-dihydroxycholecalciferol
Answer: 1, 25-dihydroxycholecalciferol
Explanation:
Ergocalciferol or Vitamin D2- Found in plants
Cholecalciferol or Vitamin D3- Found in animals
25-hydroxycholecalciferol- Prominent form of Vitamin D in the plasma and major storage form of the vitamin
1, 25-dihydroxycholecalciferol- Biological active form of Vitamin D
Q-214. First substrate of Kreb’s cycle is:
a) Pyruvate
b) Acetyl CoA
c) Fatty acid
d) Succinyl CoA
Answer: Acetyl CoA
Explanation:
Pyruvate, the end product of aerobic glycolysis, must be transported into the mitochondria before it can enter the TCA cycle.
Once in the matrix pyruvate is converted into acetyl Co-A by the pyruvate dehydrogenase complex.
The pyruvate dehydrogenase complex is not part of the TCA cycle proper but is a major source of acetyl Co-A for cycle.
Q-215. SYBR Green Dye is used for
a) HPLC
b) Immuno-fluorescence
c) PCR
d) ELISA
Answer: PCR
Explanation:
Two types of chemistries to detect PCR products using real-time PCR instruments:
TaqMan Based Detection:
Uses a fluorogenic probe specific to target gene to detect target as it accumulates during PCR.
SYBR Based Detection:
Uses SYBR Green dye (A ds-DNA binding dye) to detect PCR product as it accumulates during PCR.
Q-216. Hemoglobin electrophoresis is based on
a) Molecular weight
b) Charge
c) Solubility
d) Calorimetric properties
Answer: Charge
Explanation:
Hemoglobin electrophoresis is used as a screening test to identify variant and abnormal hemoglobins.
Alkaline and/or citrate agar electrophoresis is the commonly used method.
Separation of hemoglobins is based on variable rates of migration of charged hemoglobin molecules in an electrical field.
Q-217. Increased copper excretion in urine is seen in all except
a) Primary sclerosing cholangitis
b) Wilson’s disease
c) Primary biliary cirrhosis
d) Hepato-cellular carcinoma
Answer: Hepato-cellular carcinoma
Explanation:
The biliary system is the major pathway of copper excretion. Biliary excretion of copper requires an ATP-dependent transporter protein.
Mutations in the gene for the transporter protein cause hepato-lenticular degeneration (Wilson disease).
Ceruloplasmin, the primary copper-carrying protein in the blood, is also reduced in Wilson disease.
Urine copper excretion is increased in Wilson disease due to a decreased serum binding of copper to Ceruloplasmin, or due to allelic variances in cellular metal ion transporters.
Hypercupriuria is also found in Menkes disease (kinky hair disease), hemochromatosis, biliary cirrhosis, primary sclerosing cholangitis, Cholestatic hepatitis, thyrotoxicosis and malignant diseases (including leukemia).
Urine copper concentrations are also elevated in patients taking contraceptives or estrogens and during pregnancy.
Conditions in which there is cholestasis, there is increased accumulation of copper in the liver and increased excretion through urine.
Q-218. Peroxidase is used in estimating:
a) Glucose
b) Ammonia
c) Hemoglobin
d) Creatinine
Answer: Glucose
Explanation:
Glucose oxidase catalyze the oxidation of Beta D- glucose present in the plasma to D glucono -1 ,5 – lactone with the formation of hydrogen peroxide; the lactone is then slowly hydrolyzed to D-gluconic acid.
The hydrogen peroxide produced is then broken down to oxygen and water by a peroxidase enzyme.
Oxygen then react with an oxygen acceptor such as ortho toluidine which itself converted to a colored compound, the amount of which can be measured colorimetrically.
Q-219. Cation used in PCR
a) Li++
b) Ca++
c) Na++
d) Mg++
Answer: Mg++
Explanation:
PCR (Polymerase Chain Reaction) is a revolutionary method developed by Kary Mullis in the 1980s.
PCR is based on using the ability of DNA polymerase to synthesize new strand of DNA complementary to the offered template strand.
RT-PCR (Reverse Transcription PCR) is PCR preceded with conversion of sample RNA into cDNA with enzyme reverse transcriptase.
Material required for PCR:
DNA template
Primers
DNA polymerase (Taq polymerase)
Deoxy-ribo-nucleoside tri-phosphates (d-NTPs)
Buffer solution
Divalent cations- Mg++ or Mn++ (Generally Mg++ is used)
Monovalent cation- K+
Q-220. Molecular changes in Lysosomal Storage Disorders is
a) Defective fusion of Lysosomes and phagosomes
b) Increased synthesis of some substrates
c) Mutation of genes encoding lysosomal hydrolase
d) Membrane defect of Lysosomes
Answer: Mutation of genes encoding lysosomal hydrolase
Explanation:
All LSDs are inherited in an autosomal recessive manner, except Hunter syndrome (MPS II) and Fabry disease, which are X-linked recessive disorders.
Classically, lysosomal storage diseases encompassed only enzyme deficiencies of the lysosomal hydrolases.
More recently, the concept of lysosomal storage disease has been expanded to include deficiencies or defects in proteins necessary for the normal post-translational modification of lysosomal enzymes, activator proteins, or proteins important for proper intracellular trafficking between the lysosome and other intracellular compartments.