NEET Class 12

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 Multiple Choice QuestionsMultiple Choice Questions


Thickening of arteries due to cholesterol deposition is

  • arteriosclerosis

  • rheumatic heart

  • blood pressure

  • cardiac arrest



Thickening of arteries due to cholesterol deposition is arteriosclerosis. This is extremely widespread disease predisposes to myocardial infarction, cerebral thrombosis, and other serious illness. It is characterized by infiltration of cholesterol and appearance of foam cells in certain lesions of the arterial wall, distorting the vessels and making them rigid.


Hydroponics is

  • nutrient less culture

  • water less culture

  • soilless culture

  • none of these


soilless culture

Hydroponics is a subset of hydroculture, which is a method of growing plants without soil by using mineral nutrient solutions in a water solvent. It is useful in areas having thin, infertile and dry soils. They conserve water. It can regulate pH optimum for a particular crop, control soil borne pathogens, avoid problems of weeding and obtain consistently better yield.


Which of the following helps in ascent of sap?

  • Root pressure

  • Transpiration

  • Capillarity

  • All of these


All of these

Water is mainly absorbed by roots which goes upwards so as to replace water loss in transpiration and to be used in photosynthesis. This upward movement of water from roots to leaves through stem against force of gravity is cal led ascent of sap.

There are many theories in order to understand the ascent of sap.

  1. Root Pressure Theory-Root pressure is developed when rate of absorption is more than rate of transpiration and so water is pushed up in the tracheary elements.
  2. Capillary Force Theory- According to this, xylem vessels act as minute capillaries and water rises in these capillaries due to capillary action or surface tension.
  3. Transpiration Pull Theory- Due to water loss by transpiration suction pressure is increased and water is absorbed from adjacent xylem vessels of leaves and thus sap in under tension.


Which of the following is the connecting link between glycolysis and Krebs cycle?

  • Acetyl Co- A

  • Oxalosuccinic acid

  • Pyruvic acid

  • Citric acid


Acetyl Co- A

Glycolysis is the first step of respiration in which glucose is broken down to pyrurate.

During glycolysis 1 molecule of glucose is converted to 2 molecules of pyruvic acid in the cytoplasm. These two molecules of pyruvic acid are then converted to acetyl Co-A by decarboxylation. This acetyl Co-A is the connecting link between glycolysis and Kreb's cycle and functions as substrate entry for Kreb's cycle. Acetyl Co-A thus formed participates in Kreb's cycle and combines with oxaloacetic acid to form citrate.


Which of the following is correct set of micronutrient for plants?

  • Mg, Si, Fe, Cu, Ca

  • Cu, Fe, Zn, B, Mn

  • Mg, Fe, Zn, B, Mn

  • Mo, Zn, Cl, Mg, Ca


Cu, Fe, Zn, B, Mn

Plants require nutrients for proper growth and development. There are 16 elements which are required for plant and are termed as essential elements. They are as follows:

Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N), Phosphorus (P), Sulphur (S), Potassium (K), Magnesium (Mg), Calcium (Ca), Iron (Fe), Copper (Cu), Boron (B), Zinc (Zn), Manganese (Mn), Molybdenum (Mo) and Chlorine (Cl).

The essential elements are categorised into 2 groups,

  1. Macro- nutrients: These are required by plants in large, C, H, O, N, S, P, K, Ca and Mg.
  2. Micro- nutrients: These are required by plants in very small, Fe, Cu, B, Mn, Ni, Mo and Cl.


Velamen present in orchids helps in

  • absorption of nutrients from host plant

  • respiration

  • absorption of moisture from air

  • synthesising food


absorption of moisture from air

Some epiphytes eg., orchids have aerial roots. In these roots the outer covering is made up of a spongy tissue called velamen which absorbs moisture from the air. Thus, the aerial plant can prepare food by photosynthesis.


An example of competitive inhibition ofan enzyme is the inhibition of

  • succinic dehydrogenase by malonic acid

  • cytochrome oxidase by cyanide

  • hexokinase by glucose-6-phosphate

  • carbonic anhydrase by carbon dioxide


succinic dehydrogenase by malonic acid

An example of competitive inhibition of an enzyme is the inhibition of succinic dehydrogenase by malonic acid. lt is the simple type of competitive inhibition. A competitive inhibitor resembles the substrate and binds to the active site of the enzyme. The substrate is then prevented from binding to the same active site.


Which of the following contain β-1, 4 linkage?

  • Maltose

  • Sucrose

  • Lactose

  • Fructose



Lactose or milk sugar (carbohydrate) is reducing sugar formed through β- 1, 4 condensation between galactose and glucose. Lactose does not occur in nature except as a product of the mammary gland. It is highest in human milk as compared to that of cow, buffalo and goat. Lactose is a product of glucose, fructose and galactose.

Maltose or malt sugar is a disaccharide formed from two units of glucose joined with anα(14) bond. It is found in germinating grain, in a small proportion in corn syrup and forms on the partial hydrolysis of starch.

Sucrose or table sugar is a disaccharide where a molecule is composed of two monosaccharides, glucose and fructose. It is produced naturally in plants, from which table sugar is refined. It is extracted and refined from either sugar cane or sugar beet.

Fructose or fruit sugar is a simple ketonic monosaccharide found in many plants, where it is often bonded to glucose to form disaccharide sucrose.


Which of the following is responsible for the mechanical support, protein synthesis and enzyme transport?

  • Cell membrane

  • Mitochondria

  • Dictyosome

  • Endoplasmic reticulum


Endoplasmic reticulum

Endoplasmic reticulum functions as cytoskeleton or intracellular and ultrastructural skeletal framework by providing mechanical support to colloidal cytoplasmic matrix. Proteins and enzymes synthesized by ribosomes enter the channels of rough endoplasmic reticulum both for intracellular use as well as extracellular transport.


Which statement is true?

  • Adenine has 4 nitrogen atoms.

  • Cytosine has 3 nitrogen atoms

  • Guanosine has 3 nitrogen atoms

  • Uracil has 5 nitrogen atoms


Cytosine has 3 nitrogen atoms

Cytosine is one of the four main bases found in DNA and RNA. It is a pyrimidine derivative, with a heterocyclic aromatic ring and two substituents attached. It has 3 Nitrogen atoms.

Adenine is a purine nucleobase used in forming nucleotides of the nucleic acids. It binds to thymine via 2 hydrogen bonds to assist in stabilizing the nucleic acid structure.

Guanosine is a purine nucleoside comprising guanine attached to a ribose ring viaβ- Ng- glycosidic bond. It can be phosphorylated to become guanosine monophosphate (GMP), cyclic guanosine monophosphate (cGMP), guanosine diphosphate (GDP) and guanosine triphosphate (GTP).

Uracil is the nucleobase of RNA instead of thymine in DNA. It binds to adenine via two hydrogen bonds.