In mammals, histamine is secreted by
Fibroblasts
Histocytes
Lymphocytes
Mast cells
D.
Mast cells
Histamine is a potent vasodilator formed by decarboxylation of the amino acid histidine and released by mast cells in response to appropriate antigens.
Mast cells which secrete histamine are especially prevalent in the connective tissue of the skin and respiratory tract and in surrounding blood vessels.
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
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
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
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
