Subject

Biology

Class

NEET Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

21.

Phytotron is :

  • a controlled condition chamber for tissue

  • leaf culture process

  • special culture of plants

  • root culture process


A.

a controlled condition chamber for tissue

Phytotron is a chamber in which plants can be grown in controlled condition


22.

The S-phase of cell cycle is characterized by:

  • duplication of chromosome

  • shotening of chromosome

  • duplication of DNA

  • duplicatin of centriole


C.

duplication of DNA

The cell cycle of eukaryotic cell is divided into following four phases.

(1) G1 phase (first growth phase)

(2) S phase (synthesis phase)

(3) G2- phase (second growth phase)

(4) M-phase (mitotic phase)

S-phase is the phase is cell cycle during which DNA is replicated.


23.

Which cell organelle is covered by only one unit membrane ?

  • Nucleus

  • Plastids

  • Mitochondria

  • Lysosome


D.

Lysosome

Nucleus, Plastids, and mitochondria are double membrane bound cell organelles whereas Lysosome is covered by single membrane.


24.

Fruits are formed in :

  • Brassica

  • Fern

  • Cycas

  • Funaria


A.

Brassica

Fruit formation is the characteristic feature of Angiosperms. It is found in Brassica, Bryophytes, Pteridophytes, whereas Gymnosperms lack fruit like structure.


25.

Core of chlorophyll is formed by

  • Fe

  • Mn

  • CH3

  • Mg


D.

Mg

The chlorophylls are basically chelate salts of magnesium (Mg). The chlorophyll has a molecular formula C55H72O5N4Mg. This molecule is distinguishable into head of size 15 x 15 Å and a tail length of 20 Å. The head is made up of prophyrin ( a tetraphyrrole closed ring derivative) and the tail of phytol.


26.

Cell membrane is made up of:

  • protein

  • cellulose

  • lipids

  • lipids, carbohydrates and protein


D.

lipids, carbohydrates and protein

Plasma membrane or cell membrane is made up of approximately 60% protein and 40% lipids (by dry weight). However, the protein is found as low as 20% (human myelin) or as high as 70% (rat liver mitochondria). Carbohydrates range from 1 to 10 % in the form of glycoproteins or glycolipids.


27.

If centromere is the middle, the chromosome is called :

  • sub-metacentric

  • metacentric

  • acentric

  • telocentric


B.

metacentric

In metacentric chromosomes centromere is present in the middle of chromosome.

In sub-metacentric chromosomes the centromere is submedian.

In Acrocentric chromosome centromere is sub terminal.

In Telocentric chromosome centromere is terminal.


28.

CO2 acceptor in CAM plants is in :

  • mesophyll cells

  • bundle sheath

  • both

  • none of the above


A.

mesophyll cells

CAM or Crassulacean Acid Metabolism  is found in succulent plants. In these plants CO2 is accepted in night via Phosphoenol pyruvate carboxylase enzyme in mesophyll cells.

During night, stomata open and CO2 is stored in vacuole in the form of malic acid. During day, it is decarboxylated and CO2 is transfered to ribulose 1,5 biphosphate (RuBP) of the calvin cycle within the same cell.


29.

Quiscent centre is present in :

  • root apex

  • shoot apex

  • parenchyma

  • collenchyma


A.

root apex

Quiescent centre is present in root apex. Clowes found a reservoir of cells having low DNA, RNA and protein concentration in root apex. These cells do not divide but may become active or they can made to divide. Due to its inactivity, the quiescent centre is resistant to damages.


30.

Which hormone is responsible for mobilization of storage food during seed germination ?

  • Auxin

  • Gibberellin

  • Cytokinin

  • Ethylene


B.

Gibberellin

Gibberellin is responsible for mobilization of storage food during seed germination. After getting moisture, the embryo of seed releases gibberellins. It induces the alemone layer of endosperm to produce enzymes (e.g. α-amylase). These enzymes digest stored starch to mobilize sugars for germination.