Biochemistry & Physiology

Biochemistry & Physiology

Serum level of a drug is important to monitor, if patient is on

Lithium has narrow therapeutic index between 0.6-1.2 mEq/L with toxicity causing renal failure and neurological damage. Serum monitoring ensures efficacy, prevents accumulation due to altered clearance, dehydration, or drug interactions.

Ref: Katzung et al., Basic and Clinical Pharmacology, 14th Edition, Chapter 29 Antipsychotic and mood stabilizer agents including lithium, discusses narrow therapeutic window requiring therapeutic drug monitoring to avoid nephrotoxicity and neurotoxicity, published by Lange McGraw-Hill.

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Biochemistry & Physiology

The ratio of LD50 to ED50 is

Therapeutic index quantifies drug safety as LD50 divided by ED50, reflecting margin between median lethal and effective doses. Higher values indicate wider safety window, crucial for evaluating toxicity risk in preclinical drug development and dosing decisions.

Ref: Katzung et al., Basic and Clinical Pharmacology, 14th Edition, Chapter 2 Pharmacodynamics dose-response relationships, explains therapeutic index as LD50 divided by ED50 ratio indicating drug safety margin and toxicity evaluation, published by McGraw-Hill Education Lange.

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Biochemistry & Physiology

All have the least abuse liability, EXCEPT

Cocaine is a potent central nervous system stimulant blocking dopamine reuptake, producing euphoria and high psychological dependence. Unlike caffeine, benzodiazepines at therapeutic doses, and aspirin, it exhibits pronounced abuse liability leading to compulsive use disorders.

Ref: Nestler, Hyman and Malenka Molecular Neuropharmacology and Katzung, Basic and Clinical Pharmacology, 14th Edition, Chapter 32 Drugs of abuse including psychostimulants, describes cocaine high abuse liability via dopamine transporter blockade, published by McGraw-Hill Education.

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Biochemistry & Physiology

All are the essential roles of pharmacovigilance programme, EXCEPT

Pharmacovigilance focuses on detection, assessment, understanding, and prevention of adverse drug reactions to improve patient safety. Treatment of individual ADRs remains clinical management responsibility of physicians, not the core surveillance program's essential role.

Ref: Edwards and Aronson, Introduction to Pharmacovigilance, and WHO Pharmacovigilance Guide, Chapter 1 Objectives and WHO Programme for International Drug Monitoring, defines pharmacovigilance roles as detection, assessment, understanding and prevention of adverse drug reactions, published by Wiley and WHO Press.

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Biochemistry & Physiology

What does graph which contains substrate concentration verses velocity curve indicate?

A hyperbolic velocity versus substrate concentration plot reflects Michaelis-Menten kinetics. It depicts saturation where velocity approaches Vmax, with Km defined as substrate concentration yielding half-maximal velocity, characterizing enzyme affinity and catalytic efficiency.

Ref: Nelson and Cox, Lehninger Principles of Biochemistry, 7th Edition, Chapter 6 Enzyme kinetics including Michaelis-Menten, discusses substrate concentration versus velocity hyperbolic curve illustrating Km and Vmax determination, published by W.H. Freeman and Company.

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Biochemistry & Physiology

Which drug causes Gynecomastia, expect?

Cimetidine, spironolactone, and digoxin are well-known to cause gynecomastia via antiandrogenic effects, estrogenic activity, or altered testosterone metabolism. Fibrates, used for hyperlipidemia, are not typically associated with breast tissue proliferation.

Ref: Katzung et al., Basic and Clinical Pharmacology, 14th Edition, Chapter 40 Drugs affecting gonadal hormones and adverse endocrine effects, notes cimetidine, spironolactone, digitalis cause gynecomastia while fibrates do not commonly cause it, published by Lange McGraw-Hill.

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Biochemistry & Physiology

What is the mechanism that white blood cells used to kill bacteria, fungi and other invading organisms?

Phagocytes destroy microbes via respiratory burst generating reactive oxygen species like superoxide, hydrogen peroxide, and hypochlorous acid through NADPH oxidase and myeloperoxidase. These oxidants damage microbial membranes, proteins, and DNA intracellularly.

Ref: Murphy et al., Janeway's Immunobiology, 9th Edition, Chapter 3 Phagocyte effector mechanisms and microbicidal activity, explains respiratory burst and oxidative killing via NADPH oxidase and myeloperoxidase producing hypochlorous acid, published by Garland Science.

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Biochemistry & Physiology

What is the term used to describe white blood cell migrating towards bacteria?

Chemotaxis describes directed leukocyte migration along chemical gradients, such as bacterial formyl peptides and complement C5a. Neutrophils detect concentration differences, polarize cytoskeleton, and move toward infection sites before phagocytosis occurs.

Ref: Murphy et al., Janeway's Immunobiology, 9th Edition, Chapter 3 Inflammation and innate recruitment, describes chemotaxis as directed neutrophil migration toward bacterial peptides and chemokines via cytoskeletal reorganization, published by Garland Science.

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Biochemistry & Physiology

The blood group with anti-A antibodies and anti-B antibodies is

Group O erythrocytes lack A and B antigens, so plasma naturally contains both anti-A IgM and anti-B IgM isoagglutinins. This absence of antigens allows O to donate red cells universally but restricts recipients to O blood only.

Ref: Abbas et al., Cellular and Molecular Immunology, 9th Edition, Chapter on transplantation and Hoffbrand and Moss, Essential Haematology, 7th Edition, Chapter 22 Blood transfusion and ABO blood groups, explains isoagglutinins in group O plasma, published by Wiley-Blackwell.

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Biochemistry & Physiology

Newborns

Maternal IgG actively crosses placenta via neonatal Fc receptor (FcRn) during third trimester, providing newborns with nearly adult levels for passive protection. IgM cannot cross due to large pentameric size, limiting fetal defense.

Ref: Abbas et al., Cellular and Molecular Immunology, 9th Edition, Chapter 13 Placental transport and neonatal immunity, details neonatal Fc receptor mediated transplacental IgG transfer providing passive immunity to newborns while IgM cannot cross, published by Elsevier.

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Biochemistry & Physiology

Which of the following vaccines does not provide life time protection?

Tetanus toxoid immunity wanes within 5-10 years, requiring decennial boosters to maintain protective antitoxin titers. In contrast, replicating vaccines like smallpox and polio often induce long-lived plasma cells conferring decades-long or lifelong protection without frequent boosting.

Ref: Abbas et al., Cellular and Molecular Immunology, 9th Edition, Chapter 20 Vaccines and immunization, discusses duration of immunity, tetanus toxoid waning requiring boosters versus lifelong protection by live attenuated vaccines, published by Elsevier Saunders.

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Biochemistry & Physiology

Secondary immune response is generated due to

Memory B and T cells generated during primary response persist long-term with lower activation thresholds. Upon re-exposure, they rapidly proliferate and differentiate into plasma and effector cells, producing faster, stronger, higher-affinity secondary immune response.

Ref: Punt et al., Kuby Immunology, 8th Edition, Chapter 10 Immunological memory and secondary responses, describes memory B and T lymphocytes mediating rapid proliferation and high affinity antibody production upon re-exposure, published by W.H. Freeman.

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