Molecular Biology & Genetic Engineering

Molecular Biology & Genetic Engineering

What does uncompetitive inhibition in the enzyme-substrate reaction tells us

Uncompetitive inhibition occurs when inhibitor binds only enzyme-substrate complex, not free enzyme, at allosteric site distinct from active site. Binding requires prior substrate attachment forming ES-I dead-end complex. This reduces both Vmax and Km, unlike competitive inhibition competing for catalytic site.

Ref: Nelson and Cox, Lehninger Principles of Biochemistry, 7th Edition, Chapter 6 Enzyme Kinetics and Inhibition, describes uncompetitive inhibition inhibitor binds only enzyme substrate complex ES not free enzyme allosteric site reduced Vmax Km formation of dead end ESI complex, published by W.H. Freeman.

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Molecular Biology & Genetic Engineering

The amino acid involved in the synthesis of nitric oxide is

L-arginine serves as substrate for nitric oxide synthase producing nitric oxide and citrulline, requiring oxygen, NADPH, and tetrahydrobiopterin cofactors. NO acts as vasodilator, neurotransmitter and immune mediator via cGMP signaling. Endothelial NOS deficiency impairs vasodilation, linking arginine metabolism to hypertension.

Ref: Nelson and Cox, Lehninger Principles of Biochemistry, 7th Edition, Chapter 22 Amino Acid Metabolism and Nitrogen Oxide Signaling, explains nitric oxide synthesis from arginine by NOS isoforms producing citrulline, cofactors NADPH tetrahydrobiopterin, signaling functions vasodilation cGMP pathway, published by W.H. Freeman.

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Molecular Biology & Genetic Engineering

Acid phosphatase is a marker of

Acid phosphatase, active at acidic pH, is concentrated within lysosomes and serves as established lysosomal marker enzyme alongside cathepsins. Histochemical staining reveals lysosomal localization. Plasma membrane markers include Na+/K+ ATPase, mitochondria cytochrome oxidase, ER glucose-6-phosphatase for fractionation.

Ref: Alberts et al., Molecular Biology of the Cell, 6th Edition, Chapter 13 Intracellular Compartments, presents acid phosphatase as lysosomal marker enzyme due to acidic hydrolase localization, de Duve discovery, used for subcellular fractionation validation versus plasma membrane mitochondria ER markers, published by Garland Science.

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Molecular Biology & Genetic Engineering

Which of the following is wrong about Hemoglobin

Hemoglobin is tetrameric oxygen-transport protein with quaternary structure, each subunit containing heme prosthetic group binding oxygen cooperatively. It lacks enzymatic activity; proteolysis is function of proteases, not globins. Hemoglobin transports oxygen from lungs to tissues and returns carbon dioxide partially.

Ref: Voet, Voet and Pratt, Fundamentals of Biochemistry: Life at the Molecular Level, 5th Edition, Chapter 8 Hemoproteins, describes hemoglobin quaternary structure tetrameric heme containing oxygen binding cooperativity allosteric regulation Bohr effect absence of proteolytic catalytic activity, published by Wiley.

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Molecular Biology & Genetic Engineering

Water transportation across lipid bilayers of the cell is probably mediated by

Aquaporins are integral membrane proteins forming selective water channels facilitating rapid osmotic water transport across lipid bilayers, discovered by Peter Agre. They exclude ions via NPA motifs and selectivity filter, essential for kidney concentrating ability, RBC volume regulation, and plant turgor.

Ref: Lodish et al., Molecular Cell Biology, 8th Edition, Chapter 11 Membrane Transport, covers aquaporins integral membrane water channels discovered by Peter Agre Nobel Prize, NPA motifs selectivity filter rapid water transport, physiological roles kidney erythrocyte plant cells, published by W.H. Freeman.

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Molecular Biology & Genetic Engineering

Which of the following reduces oxygen to water?

Cytochrome c oxidase, Complex IV of electron transport chain, catalyzes four-electron reduction of molecular oxygen to two water molecules using electrons from cytochrome c. This reaction drives proton pumping across inner mitochondrial membrane, contributing to electrochemical gradient for ATP synthesis via respiration.

Ref: Nelson and Cox, Lehninger Principles of Biochemistry, 7th Edition, Chapter 19 Oxidative Phosphorylation, details cytochrome c oxidase Complex IV reducing molecular oxygen to water four electron process, proton pumping electron transport chain chemiosmotic coupling ATP synthesis, published by W.H. Freeman.

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Molecular Biology & Genetic Engineering

Coenzyme A is a derivative of

Coenzyme A derives from vitamin B5 pantothenate, incorporating cysteamine, pantothenic acid, and 3'-phosphorylated ADP moiety. It carries acyl groups as thioesters, central to TCA cycle, fatty acid metabolism, and acetylation. Pantothenate deficiency impairs CoA synthesis, affecting energy metabolism.

Ref: Nelson and Cox, Lehninger Principles of Biochemistry, 7th Edition, Chapter 16 Coenzymes and Vitamins, describes coenzyme A derivation from pantothenate vitamin B5, structure containing pantothenate cysteamine ADP phosphate, function carrying acyl thioesters TCA fatty acid oxidation, published by W.H. Freeman.

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Molecular Biology & Genetic Engineering

Valency of carbon is

Carbon possesses four valence electrons in outer shell configuration 2s2 2p2, requiring four covalent bonds to achieve octet stability. This tetravalency enables formation of single, double, triple bonds and diverse organic backbones, forming basis of organic chemistry and biomolecular diversity.

Ref: Nelson and Cox, Lehninger Principles of Biochemistry, 7th Edition, Chapter 1 Foundations, discusses carbon tetravalency four valence electrons octet rule, ability to form diverse single double triple bonds creating organic molecular diversity backbone of life, published by W.H. Freeman.

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Molecular Biology & Genetic Engineering

The primary sex organ in the male is

Testes are primary male sex organs producing spermatozoa and testosterone via seminiferous tubules and Leydig cells. Penis, seminal vesicles, prostate are accessory structures aiding transport and semen formation. Gonadal function regulated by hypothalamic-pituitary axis requiring gonadotropins FSH and LH.

Ref: Guyton and Hall, Textbook of Medical Physiology, 13th Edition, Chapter 80 Male Reproductive System, identifies testes as primary sex organs producing gametes and testosterone via seminiferous tubules Leydig cells, accessory glands role semen transport, gonadotropin regulation, published by Elsevier.

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Molecular Biology & Genetic Engineering

Hormone insulin of Pancreas is secreted by

Pancreatic beta cells located in islets of Langerhans synthesize and secrete insulin in response to elevated blood glucose. Insulin facilitates glucose uptake via GLUT4 translocation. Alpha cells secrete glucagon, delta somatostatin, pancreatic acini produce digestive enzymes, not hormones.

Ref: Barrett, Barman, Boitano and Brooks, Ganong's Review of Medical Physiology, 25th Edition, Chapter 24 Endocrine Pancreas, explains insulin secretion by pancreatic beta cells of islets of Langerhans, glucose stimulated release, GLUT4 mediated uptake versus alpha glucagon function, published by McGraw-Hill.

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Molecular Biology & Genetic Engineering

Shoulder joint is an example of

Shoulder glenohumeral joint represents ball and socket synovial joint, where humeral head articulates with glenoid cavity, permitting multiaxial movement including flexion, extension, abduction, rotation. This highly mobile configuration sacrifices stability, requiring rotator cuff support, unlike cartilaginous or fibrous joint types.

Ref: Standring et al., Gray's Anatomy: The Anatomical Basis of Clinical Practice, 41st Edition, Chapter 49 Pectoral Girdle and Shoulder, describes glenohumeral joint as synovial ball and socket joint multiaxial mobility flexion extension abduction rotation, stability sacrificed for range, published by Elsevier.

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Molecular Biology & Genetic Engineering

The movement of the sole of the foot inward or medially is _____________

Inversion turns sole of foot medially toward midline, involving subtalar and transverse tarsal joints, mediated by tibialis anterior and posterior muscles. Eversion opposite lateral movement, while pronation and supination describe combined triplane motions in weight-bearing. Clinically important for ankle sprain mechanisms assessment.

Ref: Moore, Dalley and Agur, Clinically Oriented Anatomy, 8th Edition, Chapter 6 Lower Limb, defines foot inversion medial sole movement, subtalar joint action, tibialis anterior posterior function, contrasts eversion pronation supination, clinical relevance to ankle sprains, published by Wolters Kluwer.

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