Consider statements about human immunity: 1. Colostrum provides passive immunity to infants. 2. Allergies are exaggerated immune responses. 3. Autoimmune diseases occur when the immune system attacks self-cells. Which are correct? MCQ with Answer and Explanation
Consider statements about human immunity: 1. Colostrum provides passive immunity to infants. 2. Allergies are exaggerated immune responses. 3. Autoimmune diseases occur when the immune system attacks self-cells. Which are correct?
A. 1 and 2 only
B. 2 and 3 only
C. 1 and 3 only
D. 1, 2 and 3
Answer: Option D
Solution (By JKExamLibrary)
Colostrum, the first milk produced by the mother, is rich in IgA antibodies, providing natural passive immunity to the newborn. Allergies (hypersensitivities) occur when the immune system overreacts to harmless environmental antigens (allergens). Autoimmune diseases arise when the immune system loses tolerance and mistakenly attacks the body's own healthy cells and tissues. All statements are correct.
Explanation:
Mature mammalian red blood cells (erythrocytes) lose their nucleus and other organelles during development to maximize space for hemoglobin. Thus they are anucleate. They cannot divide or repair themselves and have a lifespan of about 120 days. Neurons, leukocytes, and hepatocytes are nucleated. RBCs obtain energy through anaerobic glycolysis.
Explanation:
Scurvy is characterized by bleeding gums, impaired wound healing, and anemia due to defective collagen synthesis from lack of vitamin C (ascorbic acid). Beriberi is B₁ deficiency, pellagra B₃, night blindness vitamin A.
Explanation:
A food web is a network of food chains, showing multiple feeding relationships. Energy flow is unidirectional, and decomposers are integral.
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