The composition of blood and lymph is tested almost every year in NEET — and the trap is rarely about not knowing what blood contains. It is about confusing which protein dominates plasma versus which cell type dominates the formed elements, or mixing up lymph's composition with plasma's.
Blood is a connective tissue consisting of a fluid matrix — plasma (~55% of blood volume) — and formed elements (~45%). Plasma is ~90% water and ~7% proteins. The three major plasma proteins are albumins (most abundant, maintain osmotic balance), globulins (immune defence and transport), and fibrinogen (clotting). Plasma without clotting factors is serum — a high-frequency NEET distinction.
The formed elements are erythrocytes (RBCs), leucocytes (WBCs), and thrombocytes (platelets). RBCs are the most numerous (~5–5.5 million/mm³ in males). They are biconcave, enucleate (in mammals), and packed with haemoglobin for O₂ transport. WBCs are far fewer (~6,000–8,000/mm³) and subdivide into granulocytes (neutrophils, eosinophils, basophils) and agranulocytes (lymphocytes, monocytes). Neutrophils are the most abundant WBC type. Platelets (~1.5–3.5 lakh/mm³) are cell fragments involved in clotting.
Lymph (tissue fluid that enters lymphatic capillaries) resembles plasma but with key differences: lymph has fewer proteins and no RBCs. It carries WBCs — predominantly lymphocytes. Lymph drains into the venous system via the thoracic duct and the right lymphatic duct.
Watch-out: NEET distractors frequently swap albumin with globulin as the most abundant plasma protein, or claim lymph contains RBCs. Serum versus plasma is another recurrent one-mark question — remember, serum = plasma minus fibrinogen and clotting factors.
(Reference: NCERT Class 11 Biology Chapter 15, page 194)
Select an option to see the explanation. Wrong answers show why your choice was tempting — and name the exact trap it exploits.
Which of the following is the most abundant protein in human blood plasma?
Answer: B. Albumin is the most abundant plasma protein (~60% of total plasma proteins), responsible for maintaining colloid osmotic pressure. (NCERT Class 11 Biology Chapter 15, page 194)
Why A is wrong: A is wrong because globulins are the second-most abundant plasma protein group (~35%), involved in immune function and transport — not the most abundant.
Why C is wrong: C is wrong because fibrinogen constitutes only ~4% of plasma proteins and functions primarily in blood clotting.
Why D is wrong: D is wrong because prothrombin is a clotting factor present in trace amounts, converted to thrombin during coagulation — far less abundant than albumin.
Serum differs from plasma in that serum lacks:
Answer: D. Serum is plasma from which fibrinogen and clotting factors have been removed (consumed during clot formation). All other proteins — albumins, globulins — remain. (NCERT Class 11 Biology Chapter 15)
Why A is wrong: A is wrong because serum retains albumins; only clotting factors are removed during clot formation.
Why B is wrong: B is wrong because globulins remain in serum; they are not consumed during clotting.
Why C is wrong: C is wrong because serum still contains albumins and globulins — it is not protein-free.
Which type of white blood cell is most abundant in human blood under normal conditions?
Answer: C. Neutrophils are the most abundant WBCs, constituting 60–70% of total leucocytes. They are phagocytic granulocytes and the first responders to bacterial infection. (NCERT Class 11 Biology Chapter 15)
Why A is wrong: A is wrong because eosinophils constitute only 2–3% of WBCs; they are associated with allergic responses and parasitic infections, not the dominant cell type.
Why B is wrong: B is wrong because lymphocytes are the second-most abundant WBCs (~20–25%), not the most abundant. A common confusion since lymphocytes dominate in lymph, not in blood.
Why D is wrong: D is wrong because monocytes constitute only 6–8% of WBCs; they differentiate into macrophages in tissues.
A student observes a blood smear and finds cells that are biconcave, enucleate, and contain haemoglobin. These cells are:
Answer: A. Erythrocytes (RBCs) in mammals are biconcave and enucleate (they lose their nucleus during maturation), and are packed with haemoglobin for oxygen transport. (NCERT Class 11 Biology Chapter 15, page 194)
Why B is wrong: B is wrong because thrombocytes (platelets) are cell fragments involved in clotting; they are not biconcave discs filled with haemoglobin.
Why C is wrong: C is wrong because leucocytes (WBCs) are nucleated and do not contain haemoglobin — they function in immune defence, not gas transport.
Why D is wrong: D is wrong because lymphocytes are a type of WBC (agranulocyte) with a large nucleus; they do not carry haemoglobin.
Lymph differs from blood in which of the following ways?
Answer: A. Lymph is derived from tissue fluid that enters lymphatic capillaries. It resembles plasma but contains fewer proteins (since large proteins are not easily filtered out of capillaries) and lacks RBCs. It carries WBCs, predominantly lymphocytes. (NCERT Class 11 Biology Chapter 15)
Why B is wrong: B is wrong because the relationship is reversed: lymph lacks RBCs but does carry WBCs (especially lymphocytes).
Why C is wrong: C is wrong because lymph has fewer proteins than plasma, not more — large plasma proteins like albumin are only partially filtered into interstitial fluid.
Why D is wrong: D is wrong because lymph differs from plasma in protein concentration and cellular composition — it is not identical.
The normal count of erythrocytes per mm³ of blood in an adult human male is approximately:
Answer: D. The normal RBC count in adult males is approximately 5–5.5 million per mm³ of blood. In females it is slightly lower at 4.5–5.0 million/mm³. (NCERT Class 11 Biology Chapter 15)
Why A is wrong: A is wrong because 6,000–8,000 per mm³ is the normal range for leucocytes (WBCs), not erythrocytes. A common confusion between cell-type counts.
Why B is wrong: B is wrong because 1.5–3.5 lakh per mm³ is the normal range for thrombocytes (platelets), not RBCs.
Why C is wrong: C is wrong because 20–25 million/mm³ far exceeds the normal RBC count; no formed element reaches this concentration.
A patient's blood sample is allowed to clot in a test tube. The clear fluid obtained after removing the clot is called:
Answer: B. When blood clots, fibrinogen and clotting factors are consumed in the clot. The remaining clear fluid is serum — essentially plasma minus clotting factors. This is a standard NEET distinction. (NCERT Class 11 Biology Chapter 15)
Why A is wrong: A is wrong because plasma is the fluid portion of unclotted blood — it still contains fibrinogen. Once clotting occurs, the remaining fluid is serum, not plasma.
Why C is wrong: C is wrong because lymph is tissue fluid that has entered lymphatic vessels — it is not obtained from clotted blood in a test tube.
Why D is wrong: D is wrong because tissue fluid (interstitial fluid) is the filtrate from blood capillaries found between cells — it is not the supernatant from a clotted blood sample.
Which of the following statements about formed elements of blood is correct?
Answer: C. Platelets (thrombocytes) are cell fragments, not complete cells — they are derived from megakaryocytes in the bone marrow and lack a nucleus. They play a key role in clotting. (NCERT Class 11 Biology Chapter 15)
Why A is wrong: A is wrong because thrombocytes (platelets) are NOT nucleated cells — they are cell fragments. Calling them 'nucleated cells' is a frequent NEET distractor exploiting the term confusion between complete cells and fragments.
Why B is wrong: B is wrong because eosinophils are granulocytes, not agranulocytes. They have bilobed nuclei and granular cytoplasm. The agranulocytes are lymphocytes and monocytes.
Why D is wrong: D is wrong because monocytes are the largest WBCs (not smallest), and they are agranulocytes, not granulocytes. They differentiate into macrophages in tissues.
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Given
A question states: "Blood plasma contains three major types of proteins. Arrange them in decreasing order of their abundance."
Required
Identify the three major plasma proteins and rank them by relative abundance.
Concept
Blood plasma is ~7% protein by weight. The three principal protein fractions are albumins, globulins, and fibrinogen. Their relative proportions are well-established in NCERT (Class 11 Biology, Chapter 15).
Formula / Rule
No mathematical formula — this is a factual recall question. The key fact:• Albumins ≈ 60% of total plasma protein• Globulins ≈ 35%• Fibrinogen ≈ 4%
Substitution
Ranking: Albumin > Globulin > Fibrinogen.
Calculation
Not applicable (pure recall).
Final answer
The decreasing order of abundance is: Albumin > Globulin > Fibrinogen.
Common trap
NEET distractors often swap albumin and globulin in the ranking, or present fibrinogen as more abundant than globulins. The mnemonic "AGF — Albumin Greatest First" may help, but the underlying logic is simpler: albumin is small and abundant because it maintains osmotic pressure (a continuous, high-demand function), while fibrinogen is needed only during clotting events.
Similar NEET-style question
"Which plasma protein is responsible for maintaining colloid osmotic pressure of blood?" — Answer: Albumin. The reasoning is the same: albumin's abundance and relatively small size make it the principal contributor to oncotic pressure.
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Blood: 55% plasma + 45% formed elements (RBC: 5M/μL, no nucleus in mammals; WBC: 6-8K/μL — granulocytes + agranulocytes; platelets: 1.5-4 lakh). Plasma: 90-92% water, 6-8% proteins (albumin, globulin, fibrinogen). Lymph: tissue fluid.
-- NCERT Class 11 Biology, Chapter 15, p. 193More in Human Physiology: 33 exam traps and mistakes · 2 formulas · 1 question pattern from its other lessons.
1 question from NEET 2023. Answers verified against NTA official keys.
Page numbers are the ones printed in the current NCERT textbook (2023 rationalised edition), unless marked pre-2023. The books are free at ncert.nic.in.
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