Consider the following physiological features of mature human erythrocytes (RBCs):
(i) They are completely devoid of any cell organelles, including the nucleus, in the majority of mammals. (ii) Their biconcave shape provides a high surface-area-to-volume ratio, facilitating rapid gas exchange. (iii) They carry an iron-containing complex protein called hemocyanin which binds to oxygen. (iv) On average, their destruction takes place in the spleen after a functional span of 120 days.
Explanation: Statement (iii) is incorrect because RBCs contain haemoglobin, an iron-containing respiratory pigment, not hemocyanin. Statements (i), (ii), and (iv) are correct.
Question 52 of 100
📘 CLASS XI
Examine these statements about the chemical composition of blood plasma:
(i) Glucose, amino acids, and lipids are absent in healthy plasma as they are completely consumed by tissues. (ii) Minerals like Na+, Ca++, Mg++, and Cl- are found in plasma in small, regulated quantities. (iii) The inactive factors necessary for blood coagulation are suspended in plasma. (iv) Liquid matrix without the active proteins of defense is known as serum.
Explanation: Statement (i) is incorrect because plasma normally contains nutrients such as glucose, amino acids, and lipids. Statement (iv) is incorrect because serum is plasma without clotting factors, not without defense proteins. Statements (ii) and (iii) are correct.
Question 53 of 100
📘 CLASS XI
Study these statements regarding the functional characteristics of various leucocytes:
(i) Lymphocytes make up 20–25% of all WBCs and exist as B and T forms, managing acquired immunity. (ii) Monocytes and neutrophils move through capillary walls to engulf and digest foreign microbes. (iii) Eosinophils secrete histamine and serotonin to promote acute inflammation. (iv) Basophils comprise the largest percentage of granulocytes in healthy blood.
Explanation: Statement (iii) is incorrect because basophils secrete histamine, serotonin, and heparin, whereas eosinophils are associated with allergic reactions and resistance to infections. Statement (iv) is incorrect because basophils are the least abundant granulocytes. Statements (i) and (ii) are correct.
Question 54 of 100
📘 CLASS XI
Read the following claims regarding blood group antigens and antibodies:
(i) ABO blood grouping relies on surface glycoproteins located on the membrane of leucocytes. (ii) A person with blood group AB is a universal recipient because their plasma lacks anti-A and anti-B antibodies. (iii) A person with blood group O has both A and B antigens on their RBC surface, making them universal donors. (iv) Incompatible blood transfusions lead to severe clumping and destruction of RBCs in the recipient.
Explanation: Statement (i) is incorrect because ABO antigens are present on erythrocytes, not leucocytes. Statement (iii) is incorrect because blood group O lacks both A and B antigens. Statements (ii) and (iv) are correct.
Question 55 of 100
📘 CLASS XI
Analyze the following statements about Rh incompatibility and its clinical consequences:
(i) Rh antigen is present on the surface of erythrocytes in roughly 80% of human beings. (ii) During subsequent pregnancies of an Rh-negative mother carrying an Rh-positive foetus, maternal anti-Rh antibodies cross the placenta. (iii) Erythroblastosis fetalis causes severe anaemia and jaundice in the newborn. (iv) This condition is prevented by injecting anti-Rh antibodies into the newborn infant immediately after birth.
Explanation: Statement (iv) is incorrect because anti-Rh antibodies are administered to the Rh-negative mother immediately after the first delivery, not to the newborn. Statements (i), (ii), and (iii) are correct.
Question 56 of 100
📘 CLASS XI
Consider these statements about blood clotting mechanisms:
(i) Platelets and damaged tissues at the injury site release specific factors to trigger the clotting cascade. (ii) Prothrombin is converted to active thrombin in the presence of calcium ions and the enzyme complex thrombokinase. (iii) Fibrin threads are generated by the action of thrombokinase on soluble fibrinogen. (iv) Serum contains all clotting factors except fibrinogen.
Explanation: Statement (iii) is incorrect because thrombin converts fibrinogen into fibrin. Statement (iv) is incorrect because serum lacks all clotting factors. Statements (i) and (ii) are correct.
Question 57 of 100
📘 CLASS XI
Read the following statements regarding interstitial fluid and lymph:
(i) Interstitial fluid has a mineral distribution that is highly different from blood plasma. (ii) Lymph is a colour-rich fluid containing red blood cells and platelets. (iii) Specialized lymphocytes present in the lymph are responsible for the body's immune responses. (iv) Lacteals in the intestinal villi absorb dietary fats and transport them through the lymphatic system.
Explanation: Statement (i) is incorrect because interstitial fluid has essentially the same mineral distribution as plasma. Statement (ii) is incorrect because lymph is a colourless fluid lacking RBCs and platelets. Statements (iii) and (iv) are correct.
Question 58 of 100
📘 CLASS XI
Examine these statements about the evolutionary pattern of vertebrate hearts:
(i) Fishes have a single circulation pattern where the heart pumps out only oxygenated blood. (ii) Amphibians and reptiles (except crocodiles) have incomplete double circulation due to a single mixed ventricle. (iii) In birds and mammals, there are two separate circulatory pathways, resulting in complete double circulation. (iv) Crocodiles are an exception among reptiles, possessing a four-chambered heart with complete double circulation.
Explanation: Statement (i) is incorrect because the fish heart pumps deoxygenated blood to the gills for oxygenation. Statements (ii), (iii), and (iv) are correct.
Question 59 of 100
📘 CLASS XI
Study these anatomical details of the human heart:
(i) The heart is a mesodermally derived organ situated in the thoracic cavity slightly tilted to the left. (ii) The pericardium is a single-layered membrane that lacks any fluid. (iii) The inter-atrial septum is a thin, muscular wall separating the right and left atria. (iv) The inter-ventricular septum is a thick-walled muscular partition separating the left and right ventricles.
Explanation: Statement (ii) is incorrect because the pericardium is a double-walled membranous sac enclosing pericardial fluid. Statements (i), (iii), and (iv) are correct.
Question 60 of 100
📘 CLASS XI
Consider these statements regarding human cardiac valves:
(i) The bicuspid valve consists of two muscular flaps and guards the right atrio-ventricular opening. (ii) The tricuspid valve has three muscular cusps and guards the left atrio-ventricular opening. (iii) Semilunar valves guard the openings of ventricles into major outflow tracts. (iv) All cardiac valves strictly enforce unidirectional blood flow and prevent backflow.
Explanation: Statements (i) and (ii) are incorrect because they are interchanged. The tricuspid valve guards the right atrio-ventricular opening, whereas the bicuspid (mitral) valve guards the left atrio-ventricular opening. Statements (iii) and (iv) are correct.
