Subject

Biology

Class

NEET Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

11.

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.


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12.

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.


B.

oxidation of tannic acid in the presence of trace of iron from the knife makes it dark

When fresh fruits and vegetables are peeled or cut open, the enzyme called polyphenol oxidase (also called tyrosinase) contained in the cells is exposed to and reacts with the oxygen in the air. The reaction that occurs, which is called oxidation, is what turns the fruits and vegetables brown.


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13.

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.


14.

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


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15.

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


16.

Ectophloic siphonostele is found in

  • Osmunda and Equisetum

  • Marsilea and Botrychium

  • Adiantum and Cucurbitaceae

  • Dicksonia and Maidenhair fern.


17.

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


18.

How many genome types are present in a typical green plants cell

  • More than five

  • More than ten

  • Two

  • Three


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19.

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.


20.

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.


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