The protein-digesting enzyme secreted by the stomach wall in case of mammals is called
- A.chitinase
- B.amylase
- C.pepsin
- D.trypsin
Correct answer
Explanation
The correct answer is C, pepsin. The gastric glands in the stomach wall secrete pepsin, which begins the digestion of proteins into smaller peptides.
The chief cells of the gastric glands release pepsin in an inactive form, pepsinogen. Hydrochloric acid, secreted by other cells of the stomach lining, converts it into active pepsin and keeps the stomach strongly acidic, at a pH of about 1.5 to 2, which pepsin needs. Mucus lines the stomach wall and protects it from being digested by its own acid and enzyme.
A is wrong because chitinase breaks down chitin, found in insect shells and fungal walls; it is not the stomach's protein enzyme in mammals. B is wrong because amylase digests starch, and it comes from the salivary glands and the pancreas. D is wrong because trypsin also digests protein, but it is secreted by the pancreas and works in the small intestine, not the stomach.
Exam tip: pepsin in the stomach (acidic), trypsin from the pancreas in the small intestine (alkaline).
Practice Questions
View allWhich one of the following features is an indication for modification of stem of a plant?
- A.Presence of 'eye' on potato
- B.'Scale' found in onion
- C.'Tendril' found in pea
- D.'Hair' present in carrot
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The eyes of a potato are nodes with buds, and only a stem bears nodes and buds, so they prove that the potato is a modified stem.
Read the full explanation →Which one of the following metals is used in the filaments of photo-electric cells that convert light energy into electric energy ?
- A.Tungsten
- B.Copper
- C.Rubidium
- D.Aluminium
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Rubidium, an alkali metal like caesium, gives off electrons easily when light falls on it, so it is used in photoelectric cells.
Read the full explanation →Tooth enamel is made up of which one of the following calcium compounds ?
- A.Calcium carbonate
- B.Calcium sulphate
- C.Calcium hydroxide
- D.Calcium phosphate
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Tooth enamel is made mainly of calcium phosphate in the form of a hard crystal called hydroxyapatite. Enamel is the hardest substance in the human body, harder even than bone.
Read the full explanation →Which one of the following viruses used to be responsible for highly infectious disease Smallpox ?
- A.Adenovirus
- B.Variola virus
- C.Aichi virus
- D.Coxsackie virus
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Smallpox was caused by the variola virus, a large DNA virus of the pox family that spread from person to person through the air.
Read the full explanation →After fertilization, the fruit and the seed are produced by
- A.ovule and ovary, respectively
- B.ovary and ovule, respectively
- C.ovary, no ovule required
- D.ovule, no ovary required
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After fertilisation the ovary of the flower grows into the fruit, and each ovule inside it develops into a seed.
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