In the human respiratory system, the 'Surfactant' is a lipoprotein complex secreted by which cells to reduce surface tension in the alveoli? MCQ with Answer and Explanation

Question

In the human respiratory system, the 'Surfactant' is a lipoprotein complex secreted by which cells to reduce surface tension in the alveoli?

A. Type II alveolar cells

B. Goblet cells

C. Type I alveolar cells

D. Alveolar macrophages

Answer: Option A

Solution (By JKExamLibrary)

Pulmonary surfactant is a complex mixture of lipids (primarily dipalmitoylphosphatidylcholine) and proteins secreted by Type II alveolar cells (septal cells) in the lungs. Its primary function is to reduce the surface tension of the fluid lining the alveoli. Without surfactant, the alveoli would collapse at the end of expiration (atelectasis) due to high surface tension, making it extremely difficult to re-inflate the lungs during inspiration.

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Identify the correct statement about blood groups:

A. Group A has anti-B antibodies.

B. Group O has both A and B antigens.

C. Group AB is the universal donor.

D. Rh factor is unrelated to pregnancy complications.

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Correct Answer: Option A

Explanation:
Blood group A has A antigens and anti-B antibodies. Group O has no antigens, AB is universal recipient, Rh incompatibility can cause erythroblastosis fetalis.

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In photosynthesis, oxygen is released from:

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C. Water

D. Carbon dioxide

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Correct Answer: Option C

Explanation:
During the light reactions of photosynthesis, photolysis of water occurs at photosystem II, splitting water into protons, electrons, and molecular oxygen. The oxygen comes from water, not CO₂. This was demonstrated by using isotopically labeled oxygen (H₂O¹⁸). Glucose is formed in the Calvin cycle. Chlorophyll absorbs light but does not provide oxygen. The overall equation: 6CO₂ + 12H₂O → C₆H₁₂O₆ + 6O₂ + 6H₂O.

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Question #3

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Consider statements about ecology: 1. A food web consists of interconnected food chains. 2. Decomposers recycle nutrients. 3. Biomass decreases at higher trophic levels. Which are correct?

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Correct Answer: Option A

Explanation:
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