Multiple Choice Questions

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An example of the competitive inhibition of an enzyme is the inhibition of

  • Succinic dehydrogenase by malonic acid

  • Cytochrome oxidase by cyanide

  • Hexokinase by glucose-6-phosphate

  • Carbonic anhydrase by carbon dioxide


A.

Succinic dehydrogenase by malonic acid

Classical example of competitive inhibition is reduction of activity of succinate dehydrogenase by malonate, oxaloacetate and other anions. In competitive inhibition, a competitive inhibitor which has the resemblance with substrate molecule, competes with the substrate for the active site of an enzyme. While the inhibitor (1) occupies the active site, it prevents binding of the substrate to the enzyme.


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The quiescent centre in root meristem serves as a

  • Site for storage of food, which is utilised during maturation

  • Reservoir of growth hormones

  • Reserve for replenishment of damaged cells of the meristem

  • Region for absorption of water


In prokaryotes, chromatophores are

  • Specialised granules responsible for the colouration of cells

  • Structures responsible for organising the shape of the organism

  • Inclusion bodies lying free inside the cells for carrying out various metabolic activities

  • Internal membrane systems that may become extensive and complex in photosynthetic bacteria


In the sieve elements, which one of the following is the most likely function of P-proteins?

  • Deposition of callose on sieve plates

  • Providing energy for active translocation

  • Autolytic enzymes

  • Sealing off mechanism on wounding


Which one of the following precedes re-formation of the nuclear envelope during M-phase of the cell Cycle?

  • Decondensation from chromosome and reassembly of the nuclear lamina

  • Transcription from chromosome and reassembly of the nuclear lamina

  • Formation of the contractile ring and formation of the phragmoplast

  • Formaltion of the contractile ring and transcription from chromosomes


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Viruses that infect bacterial multiplication and cause their lysis, are called

  • Lysozymes

  • Lipolytic

  • Lytic

  • Lysogenic


A plant requires magnesium (Mg) for

  • Holding cells together

  • Protein synthesis

  • Chlorophyll synthesis

  • Cell wall development


Which one of the following pairs, is not correctly matched?

  • Abscisic acid - Stomatal closure

  • Gibberellic acid - Leaf fall

  • Cytokinin -  Cell division

  • IAA - Cell wall elongation


Two cells A and B are contiguous. Cell A has osmotic pressure 10 atm, turgor pressure-7 atm and diffusion pressure deficit 3 atm. Cell B has osmotic pressure 8 atm, turgor pressure 3 atm and diffusion pressure deficit 5 atm. The result will be

  • Movement of water from cell B to A

  • No movement of water

  • The equilibrium between the two

  • Movement of water from cell A to B


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In mammals, histamine is secreted by

  • Fibroblasts

  • Histocytes

  • Lymphocytes

  • Mast cells