NEET Class 12

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 Multiple Choice QuestionsMultiple Choice Questions


Damage to thymus in a child may lead to

  • a reduction in haemoglobin content of blood

  • a reduction in stem cell production

  • loss of antibody mediated immunity

  • loss of cell mediated immunity


loss of cell mediated immunity

Thymus gland is located in the upper part of thorax near the heart. It is a bilobed, pinkish gland. It secretes thymosin hormone, thymic humoral factor and thymopoietin. 

Proliferation of lymphocytes and differentiation of these lymphocytes into a variety of clones are induced by these factors. These clones are differentially specialized to destroy different specific category  of antigens and pathogens. Therefore, thymus gland brings fourth T- lymphocytes for cell mediated immunity.


Which of the following is the simplest amino acid?

  • Tyrosine

  • Asparagine

  • Glycine

  • Alanine



Proteins are the polymers of amino acids in which amino acids are joined by peptide bonds. Glycine has the simplest structure.



Enzymes, vitamins and hormones can be classified into a single category of biological chemicals, because all of these

  • enhance oxidative metabolism

  • are conjugated proteins

  • are exclusively synthesized in the body of a living organism as at present

  • help in regulating metabolism


help in regulating metabolism

Enzymes, vitamins and hormones are classified into a single category of biological chemical because all of them help in regulation of metabolism. 

Enzymes are a proteinaceous catalyst produced by cell and are responsible for high rate and specificity of one or more inter/ intra cellular biochemical recations.

Vitamin  is an organic substance, synthesized by plants (except Vitamin- D). 

Hormones are chemical messengers which on secretion bring about a specific and adaptive physiological response.


Centromere is required for

  • transcription

  • crossing over

  • cytoplasmic cleavage

  • movement of chromosomes towards poles


movement of chromosomes towards poles

Chromosomes are responsible for the transmission of the hereditary information from one generation to the next. Arms of the chromosome is known as chromatid. They are joined together in the centre known as centromere or primary constriction. During cell division, spindle fibres attach to centromere and help in the movement towards the poles.


G-6-P dehydrogenase deficiency is associated with haemolysis of

  • lymphocytes

  • RBCs

  • platelets

  • leucocytes



G-6-P dehydrogenase deficiency is associated with haemolysis of RBCs.


The net pressure gradient that causes the fluid to filter out of the glomeruli into the capsule is

  • 20 mm Hg

  • 75 mm Hg

  • 30 mm Hg

  • 50 mm Hg


20 mm Hg

Kidneys help in the formation of urine, from the blood flowing through glomerular capillaries. About 20% of plasma fluid filters out into the Bowman's capsule through a thin glomeular- capsular membrane due to a net or effective filtration of about 10 to 15 mm Hg.


Nucleotide are building blocks of nucleic acids, nucleotide is a composite molecule formed by

  • (base-sugar-phosphate)n

  • base-sugar-OH

  • base-sugar-phosphate

  • sugar-phosphate



Nucleotides are the building blocks of nucleic acids (DNA/ RNA). A single nucleotide comprises of-

(i) phosphate molecule

(ii) a five carbon sugar (either ribose or deoxyribose) 

(iii) a purine (adenine or guanine) or a pyrimidine (thymine or cytosine or uracil) nitrogenous base.

Nucleoside = Base + Sugar

Nucleotide = Base + Sugar + Phosphate


Which of the following substances, if introduce in the blood stream, would cause coagulation, at the site of its introduction?

  • Fibrinogen

  • Prothrombin

  • Heparin

  • Thromboplastin



Lipoproteinaceous, thromboplastin is released by the injured tissue. It reacts with Ca2+ ions present in blood and forms prothrombinase enzyme. Later, in the presence of Ca2+ ions, it inactivates heparin (anticoagulant) and catalyses prothrombin (inactive plasma protein) into an active thrombin protein. 

Thrombin acts as an enzyme and catalyses fibrinogen (soluble plasma protein) into an insoluble  fibre like polymer, fibrin. These form a dense network upon the wound and trap blood corpuscles and thus form a clot. This further seals the wound and stops bleeding

In blood vessels, thromboplastin does not release due to which blood does not clot. However, external thromboplastin causes blood clotting at the site of its introduction due to formation of prothrombinase enzyme.


A student wishes to study the cell structure under a light microscope having 10X eyepiece and 45X objective. He should illuminate the object by which one of the following colours of light so as to get the best possible resolution?

  • Yellow

  • Green

  • Blue

  • Red



Resolving Power or resolution is the ability of the lens to distinguish fine details and structure. It is the ability of a lens to differentiate between two points at a specified distance apart. 

Resolving Power =Wavelength of light2 × NA

It depends upon 2 factors:

(i) Wavelength of light used for illumination

(ii) Power of objective lenses

Among Yellow, green, red and blue light; Blue colour has the shortest wavelength so, it will give best resolution.


In a man, abducens nerve is injured. Which one ofthe following functions will be affected?

  • Movement of the eye ball

  • Swallowing

  • Movement of the tongue

  • Movement of the neck


Movement of the eye ball

Abducens (abducent) nerve is a cranial nerve which originates from the ventral surface of medulla oblongota. It innervates the lateral rectus muscle of eye ball. It is a motor nerve and controls the movements of the eye ball. Hence, if this nerve is injured in a human, movement of eye ball will be affected.