If by an unknown accident the acid secreting cells of the stomach wall of an individual are damaged, digestion of which one of the following biomolecule will be affected to a greater extent?
- A.Protein only
- B.Lipid
- C.Carbohydrate only
- D.Protein and Carbohydrate
Correct answer
Explanation
The correct answer is A, Protein only. The acid-secreting cells of the stomach, called oxyntic or parietal cells, release hydrochloric acid, which protein digestion in the stomach depends on. Pepsin, the main protein-digesting enzyme of the stomach, is secreted in an inactive form, pepsinogen, by the chief cells. Hydrochloric acid converts pepsinogen into active pepsin and keeps the stomach at a pH of about 1.5 to 2, at which pepsin works best. Without the acid, pepsin stays inactive, so the breakdown of proteins into peptides in the stomach suffers most. The acid also kills germs that come in with food. Option B is wrong because lipids are digested mainly in the small intestine by pancreatic lipase after bile emulsifies them; stomach acid plays little part. Option C is wrong because carbohydrates are digested by salivary amylase in the mouth and by pancreatic amylase in the small intestine, neither of which needs stomach acid. Option D is wrong because carbohydrate digestion does not depend on the acid-secreting cells, so only protein digestion is badly affected. Exam tip: HCl activates pepsinogen to pepsin; oxyntic cells make HCl, chief cells make pepsinogen.
Practice Questions
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- B.5 cm
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- D.10 cm
Show answer
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- D.soya bean and milk.
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- A.AgF
- B.AgBr
- C.AgCl
- D.Ag2SO4
Show answer
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Read the full explanation →Which one of the following statements about speed and velocity is correct?
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- B.Speed and velocity both are scalar quantities.
- C.Speed is vector quantity and velocity is scalar quantity.
- D.Speed is scalar quantity and velocity is vector quantity.
Show answer
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