Enzymes, vitamins and hormones can be classified into a single category of biological chemicals because of all of these
enhance oxidative metabolism
are conjugated proteins
are exclusively synthesised in the body of a living organism as at present
help in regulating metabolism.
Cut surfaces of fruit and vegetables often become dark because
dirty knife makes it dark
oxidation of tannic acid in the presence of trace of iron from the knife makes it dark
dust of the air makes it dark
none of the above.
In succulent plants the stomata open in night and close in day. Which among the following would be best hypothesis to explain the mechanism of stomatal action in night only.
CO2 accumulates, reduces pH, stimulate enzymes resulting in accumulation of sugars.
Increase in CO2 concentration, conversion of organic acids into starch resulting in the increased conversion into sugars resulting in K+ transport.
Low CO2 concentration accumulates organic acids resulting in the increased concentration of cell sap.
CO2 used up, increase pH results in accumulation of sugars.
B.
Increase in CO2 concentration, conversion of organic acids into starch resulting in the increased conversion into sugars resulting in K+ transport.
In CAM plants stomata open at night. In these plants night acidification occurs. i.e., malic acid is
synthesised during night due to incomplete oxidation of carbohydrates.
In night. 2 C 6H12O6+ 3 O2 3 C 4H6O5+ 3H2O
(malic acid)
leads to opening of stomata
At night malic acid formed in guard cells dissociates into H and malate ions. K ion exchange from subsidiary cells with H ions. Thus due to accumulation of K ions osmotic pressure of guard cells increases, endosmosis occurs and guard cells become turgid due to which stomata opens. The malic acid at clay time breaks into CO2 and pyruvic acid thus increasing the concentration of CO2 in mesophyll cells. This is utilised in Calvin cycle to form sugar which is finally converted into starch.
The cells of the quiescent centre are characterised by
having dense cytoplasm and prominent nuclei
having light cytoplasm and small nuclei
dividing regularly to add to the corpus
dividing regularly to add to tunica
Thermococcus, Methanococcus and Methanobacterium exemplify
bacteria whose DNA is relaxed or positively supercoiled but which have a cytoskeleton as well as mitochondria
bacteria that contain a cytoskeleton and ribosomes
archaebacteria that contains protein homologous to eukaryotic core histones
archaebacteria that lack any histones resembling those found in eukaryotes but whose DNA is negatively supercoiled
Ectophloic siphonostele is found in
Osmunda and Equisetum
Marsilea and Botrychium
Adiantum and Cucurbitaceae
Dicksonia and Maidenhair fern.
Chlorenchyma is known to develop in the
cytoplasm of Chlorella
mycelium of a green mould such as Aspergillus
spore capsule of a moss
pollen tube of Pinus
How many genome types are present in a typical green plants cell
More than five
More than ten
Two
Three
Assertion: Protoplasmic continuity is maintained in perforated septum.
Reason: Usually a small pore remains in the centre of the septum.
If both assertion and reason are true and reason is the correct explanation of assertion
If both assertion and reason are true but reason is not the correct explanation of assertion
If assertion is true but reason is false
If both assertion and reason are false.
Assertion: The primary protenema of moss by death and decay of cells may break into fragments.
Reason: Each fragment gives rise to leafy gametophyte.
If both assertion and reason are true and reason is the correct explanation of assertion
If both assertion and reason are true but reason is not the correct explanation of assertion
If assertion is true but reason is false
If both assertion and reason are false.