There are a large variety of over-the-counter pregnancy tests, although all of them share a set of common principles. These home pregnancy tests are immunoassays which detect the presence of the peptide hormone human chorionic gonadotropin (hCG). hCG is produced by the fertilised ovum and released into the mother's bloodstream, preventing the degradation of the corpus luteum and thereby preventing menstruation. By the time of the mother's first missed period, hCG levels in the urine are high enough to detect.The home pregnancy test generally involves dipping a stick containing immobilised hCG monoclonal antibodies into a urine sample. If hCG is present in the urine, it will bind to the monoclonal antibodies on the dipstick. The dipstick is then placed in a solution containing a second monoclonal antibody which recognizes the bound hCG antibody complex on the surface of the dipstick. This second antibody is conjugated to colloidal gold particles which change colour when they are immobilised, indicating a positive test result (i.e., pregnancy).The mechanism by which hCG acts on its target cells is most similar to that of _.
Correct answer: C. Glucagon
- A. Progesterone
- B. Testosterone
- C. Glucagon
- D. Estradiol
Explanation
From the passage we learn that hCG is a peptide hormone. Peptide hormones act by binding to receptors on the plasma membranes of their target cells. This binding then triggers a signalling cascade which results in the transcription of specific genes. Peptide hormones can't cross the plasma membrane directly because they are not lipid soluble. Glucagon is a peptide hormone secreted by the alpha cells of the pancreas; it therefore uses a similar mechanism to that of hCG.The other answer choices can be eliminated because they are steroid hormones. These act by directly crossing the plasma membrane and binding to receptors either in the cytoplasm or in the nucleus.
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About Chemical Coordination and Hormones
Chemical coordination uses hormones released by endocrine glands and carried in blood to specific target cells. Coverage includes the pituitary, thyroid, pancreas, adrenal glands, ovaries and testes, feedback control, and the contrast between slower, longer-lasting hormonal responses and rapid nervous coordination.
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