Blood

The red color of blood is due to: (BPSC 66th Prelims)
a) Plasma
b) Hemoglobin
c) White blood cells
d) Platelets
Answer: b
Explanation: Hemoglobin is the iron-containing pigment in red blood cells that gives blood its red color.
Which among the following is a universal recipient blood group? (BPSC 65th Prelims)
a) O+
b) AB+
c) AB−
d) A+
Answer: b
Explanation: AB+ individuals can receive blood from all blood types because they have no antibodies against A, B, or Rh antigens.
Blood is: (UPPSC 2020)
a) Muscular tissue
b) Connective tissue
c) Epithelial tissue
d) Nervous tissue
Answer: b
Explanation: Blood is considered a connective tissue due to its origin in mesoderm and its role in connecting different body parts.
Which blood cells are responsible for clotting? (BPSC 63rd Prelims)
a) RBCs
b) WBCs
c) Platelets
d) Lymphocytes
Answer: c
Explanation: Platelets or thrombocytes help in the clotting of blood by releasing clotting factors.
What is the average life span of red blood cells (RBCs)? (UPSC Prelims 2021)
a) 60 days
b) 90 days
c) 120 days
d) 150 days
Answer: c
Explanation: RBCs live approximately 120 days in circulation before being destroyed in the spleen.
Which component of blood helps in immunity? (BPSC 64th Prelims)
a) RBCs
b) Platelets
c) WBCs
d) Plasma
Answer: c
Explanation: White Blood Cells (WBCs) are the primary cells involved in immune defense.
Which blood group is known as the universal donor? (BPSC 67th Prelims)
a) AB+
b) AB−
c) O−
d) O+
Answer: c
Explanation: O− blood lacks A, B, and Rh antigens, making it safe for all recipients in emergencies.
What is the normal pH of human blood? (BPSC 66th Prelims)
a) 6.8
b) 7.4
c) 8.2
d) 7.0
Answer: b
Explanation: Blood has a slightly alkaline pH of about 7.4 to maintain homeostasis.
In humans, the blood circulation is: (UPPSC 2021)
a) Open and single
b) Closed and single
c) Open and double
d) Closed and double
Answer: d
Explanation: Humans have closed double circulation—blood passes twice through the heart during one complete cycle.
Which part of blood carries hormones? (BPSC 65th Prelims)
a) RBC
b) Plasma
c) Platelets
d) WBC
Answer: b
Explanation: Plasma transports hormones, nutrients, waste, and other substances throughout the body.

NCERT-Based Questions (Q11–30)

Which cells in the blood are biconcave and without nuclei?
a) WBCs
b) Platelets
c) RBCs
d) Lymphocytes
Answer: c
Explanation: RBCs are biconcave in shape and lack nuclei to maximize oxygen-carrying capacity.
Which protein in blood helps in oxygen transport?
a) Albumin
b) Hemoglobin
c) Fibrinogen
d) Globulin
Answer: b
Explanation: Hemoglobin binds oxygen and transports it to tissues.
What is the function of plasma in blood?
a) Blood clotting
b) Fighting infection
c) Transporting substances
d) Carrying oxygen
Answer: c
Explanation: Plasma transports nutrients, hormones, and waste products.
What is the most abundant component of blood?
a) RBCs
b) WBCs
c) Plasma
d) Platelets
Answer: c
Explanation: Plasma makes up about 55% of total blood volume.
Which of the following is not found in plasma?
a) Water
b) Salts
c) Hormones
d) Hemoglobin
Answer: d
Explanation: Hemoglobin is inside RBCs, not found in plasma.
Platelets are formed in:
a) Liver
b) Spleen
c) Bone marrow
d) Kidney
Answer: c
Explanation: Platelets originate from megakaryocytes in red bone marrow.
Which vitamin is necessary for blood clotting?
a) Vitamin A
b) Vitamin B12
c) Vitamin K
d) Vitamin D
Answer: c
Explanation: Vitamin K is essential for the synthesis of clotting factors.
Which blood cell can change its shape and pass through capillary walls?
a) RBCs
b) WBCs
c) Platelets
d) All of the above
Answer: b
Explanation: WBCs are capable of amoeboid movement and can exit the bloodstream.
The liquid portion of blood without clotting factors is called:
a) Plasma
b) Serum
c) Lymph
d) Hemolymph
Answer: b
Explanation: Serum is plasma without clotting factors.
The iron in hemoglobin binds to:
a) Glucose
b) DNA
c) Oxygen
d) CO2
Answer: c
Explanation: Iron in hemoglobin binds to oxygen molecules for transport.
Which WBC type produces antibodies?
a) Monocytes
b) Neutrophils
c) Lymphocytes
d) Eosinophils
Answer: c
Explanation: B-lymphocytes produce antibodies to fight infections.
What is the total blood volume in an average adult human?
a) 2–3 liters
b) 4–5 liters
c) 6–7 liters
d) 8–9 liters
Answer: b
Explanation: The average adult has about 4.5–5.5 liters of blood.
Which organ destroys old RBCs?
a) Liver
b) Heart
c) Spleen
d) Kidney
Answer: c
Explanation: The spleen filters and removes old or damaged RBCs.
Which of the following is the largest WBC?
a) Monocyte
b) Lymphocyte
c) Neutrophil
d) Eosinophil
Answer: a
Explanation: Monocytes are the largest WBCs and can differentiate into macrophages.
Blood clotting is also called:
a) Hemolysis
b) Coagulation
c) Agglutination
d) Thrombosis
Answer: b
Explanation: Coagulation is the process of blood clotting to prevent bleeding.
The ABO blood group was discovered by:
a) Karl Landsteiner
b) Edward Jenner
c) Alexander Fleming
d) Watson and Crick
Answer: a
Explanation: Karl Landsteiner discovered the ABO blood group system in 1901.
In fetal life, RBCs are formed in:
a) Spleen
b) Liver
c) Bone marrow
d) Thymus
Answer: b
Explanation: The liver is a primary site of RBC production during fetal development.
Hemophilia is a disorder of:
a) RBC destruction
b) Lack of clotting
c) Excess WBCs
d) Dehydration
Answer: b
Explanation: Hemophilia is a genetic disorder causing failure of blood to clot properly.
The blood group which lacks antigens A and B is:
a) AB
b) A
c) B
d) O
Answer: d
Explanation: Blood group O lacks both A and B antigens.
Rh factor is a type of:
a) Enzyme
b) Vitamin
c) Antigen
d) Hormone
Answer: c
Explanation: Rh factor is an antigen present on the surface of RBCs.

Predicted/Reference Book-Based Questions (Q31–50)

What percentage of blood is made up of cells?
a) 25%
b) 35%
c) 45%
d) 55%
Answer: c
Explanation: About 45% of blood volume is cellular elements, mainly RBCs.
Which blood component is mainly responsible for viscosity?
a) WBCs
b) Platelets
c) RBCs
d) Plasma
Answer: c
Explanation: The presence and number of RBCs largely determine the viscosity of blood.
Leukemia affects:
a) RBCs
b) Platelets
c) WBCs
d) Plasma
Answer: c
Explanation: Leukemia is cancer of WBCs, leading to their uncontrolled production.
Which plasma protein maintains osmotic pressure?
a) Fibrinogen
b) Globulin
c) Albumin
d) Hemoglobin
Answer: c
Explanation: Albumin helps maintain osmotic pressure in blood vessels.
Which component of blood helps in defense against parasites?
a) Basophils
b) Neutrophils
c) Eosinophils
d) Monocytes
Answer: c
Explanation: Eosinophils fight parasites and play a role in allergic reactions.
Normal platelet count in blood is:
a) 1–2 lakh/mm³
b) 2–3 lakh/mm³
c) 3–4 lakh/mm³
d) 4–5 lakh/mm³
Answer: b
Explanation: Normal platelet count ranges from 1.5 to 4 lakh/mm³, with ~2.5 lakh/mm³ being average.
Which hormone regulates RBC production?
a) Renin
b) Erythropoietin
c) Oxytocin
d) Insulin
Answer: b
Explanation: Erythropoietin, secreted by kidneys, stimulates RBC production in bone marrow.
What is the function of basophils?
a) Antibody production
b) Histamine release
c) Oxygen transport
d) Coagulation
Answer: b
Explanation: Basophils release histamine during allergic reactions and inflammation.
Antigens are present on:
a) Plasma
b) Antibodies
c) RBC membrane
d) WBCs
Answer: c
Explanation: Antigens of blood groups are found on the surface of RBCs.
What is the result of mismatched blood transfusion?
a) Infection
b) Fever
c) Agglutination
d) Hemorrhage
Answer: c
Explanation: Mismatched transfusion causes agglutination or clumping of RBCs due to antigen-antibody reactions.
Hematocrit refers to:
a) Clotting time
b) WBC percentage
c) Volume percentage of RBCs
d) Platelet count
Answer: c
Explanation: Hematocrit is the percentage of blood volume occupied by RBCs.
Which blood cell is phagocytic in nature?
a) Lymphocyte
b) Neutrophil
c) Basophil
d) Eosinophil
Answer: b
Explanation: Neutrophils engulf and digest pathogens by phagocytosis.
Thalassemia affects:
a) Hemoglobin synthesis
b) Platelet function
c) Plasma proteins
d) White blood cells
Answer: a
Explanation: Thalassemia is a genetic disorder affecting hemoglobin chain formation.
Blood group AB has which antibodies?
a) Anti-A
b) Anti-B
c) Both
d) None
Answer: d
Explanation: AB blood group has no antibodies, making it a universal recipient.
Excess RBC production is known as:
a) Anemia
b) Leukemia
c) Polycythemia
d) Hemophilia
Answer: c
Explanation: Polycythemia is a condition where the RBC count is abnormally high.
Which part of blood helps in repair of damaged tissues?
a) Plasma
b) WBCs
c) RBCs
d) Platelets
Answer: d
Explanation: Platelets release growth factors that help in tissue repair.
Which gas has highest affinity for hemoglobin?
a) CO₂
b) CO
c) O₂
d) N₂
Answer: b
Explanation: Carbon monoxide (CO) binds hemoglobin more strongly than oxygen, leading to poisoning.
Blood is prevented from clotting in vessels due to:
a) Lack of platelets
b) High RBCs
c) Presence of heparin
d) Plasma antibodies
Answer: c
Explanation: Heparin is an anticoagulant that prevents clotting inside blood vessels.
Which cell is the first to arrive at an infection site?
a) Basophil
b) Neutrophil
c) Monocyte
d) Lymphocyte
Answer: b
Explanation: Neutrophils are the first responders to infection and inflammation.
Atherosclerosis is related to:
a) Liver
b) Brain
c) Blood vessels
d) Kidney
Answer: c
Explanation: Atherosclerosis involves plaque buildup inside arteries, restricting blood flow.