Q-51. Which of the following substances acts to increase the release of Ca++ from endoplasmic reticulum?
a) Inositol tri-phosphate
b) Parathyroid hormone
c) 1.25-Dihydroxy Cholecalciferol
d) Diacylglycerol
Answer: Inositol tri-phosphate
Explanation:
Inositol tri-phosphate and diacylglycerol mediate the mobilization of intra-cellular calcium and the activation of protein kinase C, respectively which act synergistically to evoke specific cellular responses.
Q-52. A small Ca+2 binding protein that modifies the activity of many enzymes and other proteins in response to changes of Ca2+ concentration is known is
a) Cyclin
b) Calmodulin
c) Collagen
d) Kinesin
Answer: Calmodulin
Explanation:
Calmodulin is calcium binding and calcium dependent regulatory protein that is homologous to the muscle protein troponin C in structure and function.
Calmodulin has four calcium binding sites, and full occupancy of these sites lead to a marked conformational change, which allows calmodulin to activate enzymes and ion channels.
Q-53. A person on a fat free carbohydrate rich diet continues to grow obese. Which of the following lipoproteins is likely to be elevated in his blood?
a) Chylomicrons
b) VLDL
c) LDL
d) HDL
Answer: VLDL
Explanation:
Factors that enhance both the synthesis and secretion of VLDL by the liver include:
The fed state
The feeding of diets high in carbohydrate leading to high rates of lipogenesis and esterification
High levels of circulating free fatty acids
Ingestion of ethanol
The presence of high concentration of insulin and low concentration of Glucagon
Q-54. A middle aged woman on oral contraceptives for many years developed neurological symptoms such as depression, irritability, nervousness and mental confusion. Her hemoglobin level was 8 g/dl. Biochemical investigations revealed that she was excreting highly elevated concentrations of xanthurenic acid in urine. She also showed high levels of triglycerides and cholesterol in serum.
All of the above findings are most probably related to Vitamin B6 deficiency caused by prolonged oral contraceptive use except:
a) Increased urinary Xanthurenic acid excretion
b) Neurological symptoms by decreased synthesis of biogenic amines
c) Decreased hemoglobin level
d) Increased triglyceride and cholesterol level
Answer: Increased triglyceride and cholesterol level
Explanation:
Pyridoxal phosphate is a coenzyme for many enzymes involved in amino acid metabolism, especially transamination and decarboxylation.
It is also the cofactor of glycogen phosphorylase, where the phosphate group is catalytically important.
Pyridoxine deficiency has been observed in:
Patient s taking isoniazid
New born infants fed formulas low in Vitamin B6
Women taking oral contraceptives
Alcoholics
Pyridoxine deficiency symptoms:
Increased urinary Xanthurenic acid excretion
Decreased hemoglobin level
Neurological symptoms- Peripheral neuropathy, seizures in infants and abnormal EEG
Important point:
Isoniazid can induce a B6 deficiency by forming an inactive derivative with Pyridoxal phosphate.
Q-55. Which of the following elements is known to influence the body’s ability to handle oxidative stress?
a) Calcium
b) Iron
c) Potassium
d) Selenium
Answer: Selenium
Explanation:
In erythrocytes and other tissues, the enzyme glutathione peroxidase, containing selenium as a prosthetic group, catalyzes the destruction of H2O2 and lipid hydro-peroxide through conversion of reduced glutathione to its oxidized form, protecting membrane lipids and hemoglobin against oxidation by peroxides.
Q-56. In which of the following conditions, the level of creatinine kinase-1 increases
a) Myocardial ischemia
b) Brain ischemia
c) Kidney damage
d) Electrical cardioversion
Answer: Brain ischemia
Explanation:
Creatinine kinase-1: Brain
Creatinine kinase-2: Myocardium
Creatinine kinase-3: Skeletal muscle
Q-57. A young man finds that every time he eats dairy products he feels very uncomfortable. His stomach becomes distended. He develops gas and diarrhea frequently. These symptoms do not appear when he eats foods other than dairy products. Which of the following is the most likely enzyme in which this young man is deficient?
a) Alpha-amylase
b) Beta-galactosidase
c) Alpha-glucosidase
d) Sucrase
Answer: Sucrase
Explanation:
Presentation of lactase deficiency or sucrase-isomaltase deficiency:
Bloating
Watery diarrhoea
Failure to thrive
Recurrent vague abdominal pain
Q-58. Cytochrome C of the bacteria has 50% identity of amino acid sequence with that of human. Which of the following is the most conserved parameter in these two proteins?
a) Quaternary structure
b) Tertiary structure
c) Amino acid sequence
d) Loop and turn segments
Answer: Tertiary structure
Explanation:
Tertiary structure of Cytochrome C of bacteria and humans is the most conserved parameter in these two proteins. They are distant to each other in primary structure (Total number of amino acids and sequence of amino acids).
Q-59. Alpha helix and beta pleated sheet are examples of
a) Primary structure
b) Secondary structure
c) Tertiary structure
d) Quaternary structure
Answer: Secondary structure
Explanation:
Secondary structure:
Alpha helix
Beta pleated sheet
Loops and Bends
Q-60. A genetic disorder renders fructose 1, 6– bi-phosphatase in liver less sensitive to regulation by fructose 2, 6-bi-phosphate. All of the following metabolic changes are observed in this disorder except
a) Level of fructose 1, 6-biphosphate is higher than normal
b) Level of fructose 1, 6 bi-phosphate is lower than normal
c) Less pyruvate is formed
b) Less ATP is generated
Answer: Level of fructose 1, 6-biphosphate is higher than normal
Explanation:
Fructose 1, 6– bi-phosphatase is under negative feedback control of fructose 2, 6-bi-phosphate.
Increased fructose 1, 6– bi-phosphatase activity> Increased cleavage of fructose 1, 6-biphosphate into fructose 6 phosphate> Decreased level of fructose 1, 6-biphosphate