Year-wise Biology practice

NEET 2021 Biology PYQs

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100 questions in this collection · Page 7 of 10

Question 61 of 100
🟢 NEET 2021 📘 CLASS XI

Cell Cycle And Cell Division

Which stage of meiotic prophase shows terminalisation of chiasmata as its distinctive feature?
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Question 62 of 100
🟢 NEET 2021 📘 CLASS XI

Cell Cycle And Cell Division

The centriole undergoes duplication during:
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Question 63 of 100
🟢 NEET 2021 📘 CLASS XI

Digestion And Absorption

Succus entericus is referred to as:
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Question 64 of 100
🟢 NEET 2021 📘 CLASS XI

Digestion And Absorption

Sphincter of oddi is present at:
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Question 65 of 100
🟢 NEET 2021 📘 CLASS XI

Breathing And Exchange Of Gases

The partial pressures (in mm Hg) of oxygen (O2) and carbon dioxide (CO2) at alveoli (the site of diffusion) are :
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Question 66 of 100
🟢 NEET 2021 📘 CLASS XI

Breathing And Exchange Of Gases

Select the favourable conditions required for the formation of oxyhaemoglobin at the alveoli.
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Question 67 of 100
🟢 NEET 2021 📘 CLASS XI

Body Fluids And Circulation

Which enzyme is responsible for the conversion of inactive fibrinogens to fibrins?

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Explanation:

Thrombin is the enzyme that converts soluble fibrinogen into insoluble fibrin strands, forming a clot. In the coagulation cascade, prothrombin is activated to thrombin, which then acts on fibrinogen to produce fibrin. This process is described in NCERT under digestive–circulatory related chapters, explaining how clot formation involves thrombin as the key enzyme.

🧠 Did You Know?

Renin helps convert angiotensinogen to angiotensin, influencing blood pressure, not fibrin formation. Epinephrine can affect blood flow and clotting indirectly but does not convert fibrinogen to fibrin. Thrombokinase is an older term sometimes used for the prothrombin activator complex that leads to thrombin formation, not the direct conversion of fibrinogen to fibrin.

💡 NCERT Memory Line:

Thrombin converts fibrinogen into fibrin, forming the mesh of a blood clot as described in NCERT biology chapters on blood coagulation.

Question 68 of 100
🟢 NEET 2021 📘 CLASS XI

Body Fluids And Circulation

Persons with 'AB' blood group are called as "Universal recipients". This is due to:

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Explanation:

People with AB blood group have both A and B antigens on their RBCs and no antibodies against A or B in the plasma. Therefore, they can receive blood from any ABO type without agglutination, making them universal recipients. The correct reason is the absence of anti-A and anti-B antibodies in plasma.

🧠 Did You Know?

In contrast, individuals with type O blood have anti-A and anti-B antibodies in their plasma, so they can donate to anyone but can receive only from type O.

💡 NCERT Memory Line:

Universal recipient AB: has both A and B antigens on RBCs and no anti-A or anti-B antibodies in plasma.

Question 69 of 100
🟢 NEET 2021 📘 CLASS XI

Locomotion And Movement

Chronic auto immune disorder affecting neuro muscular junction leading to fatigue, weakening and paralysis of skeletal muscle is called as:
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Question 70 of 100
🟢 NEET 2021 📘 CLASS XI

Chemical Coordination And Integration

Erythropoietin hormone which stimulates R.B.C. formation is produced by:

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Explanation:

Erythropoietin, which stimulates red blood cell formation, is produced mainly by the juxtaglomerular cells of the kidney. It is released in response to low oxygen levels in the blood and promotes erythropoiesis in the bone marrow.

🧠 Did You Know?

Although the kidney is the primary source, small amounts of erythropoietin can be produced elsewhere, but the major site is the kidney.

💡 NCERT Memory Line:

Erythropoietin is produced by the juxtaglomerular cells of the kidney and stimulates red blood cell formation in the bone marrow.

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