NEET 2019 · Class 11

Chemical Coordination and Integration

[DIAGRAM: A protein hormone outside the cell binds to a membrane receptor on the plasma membrane, producing Response I inside the cell through a second messenger pathway that leads to a physiological response.] Identify A, B and C in the diagrammatic representation of the mechanism of hormone action.

  1. (A)A = Protein hormone; B = Cyclic AMP; C = Hormone-receptor complex
  2. (B)A = Steroid hormone; B = Hormone-receptor complex; C = Protein
  3. (C)A = Protein hormone; B = Receptor; C = Cyclic AMP
  4. (D)A = Steroid hormone; B = Receptor; C = Second messenger

The NCERT line that answers it

Verbatim line

Hormones which interact with membrane-bound receptors normally do not enter the target cell, but generate second messengers (e.g., cyclic AMP, $IP_3$ , $Ca^{++}$ etc) which in turn regulate cellular metabolism (Figure 19.5a).

Chapter
Chemical Coordination and Integration
Section
19.4 MECHANISM OF HORMONE ACTION

The answer appears as a continuous sentence in NCERT. This is that sentence.

How this line gives the answer

0, emb=1.0, combined=1.0). Verified: high — The span explicitly states that protein hormones interacting with membrane-bound receptors generate second messengers like cyclic AMP, which directly matches the diagram labels A=Protein hormone, B=Receptor, C=Cyclic AMP.

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