Which of the following mineral acids is found in human stomach ?
- A.Hydrochloric acid
- B.Lactic acid
- C.Uric acid
- D.Methanoic acid
Correct answer
Explanation
The correct answer is A, Hydrochloric acid. The gastric glands in the stomach wall secrete hydrochloric acid, the only mineral (inorganic) acid among the options.
Hydrochloric acid (HCl) makes the stomach strongly acidic, with a pH of about 1.5 to 3.5. This acidity kills most germs that enter with food and converts the inactive enzyme pepsinogen into pepsin, which begins the digestion of proteins. A layer of mucus protects the stomach lining from the acid; too much acid causes acidity, which antacids such as magnesium hydroxide neutralise.
B is wrong: lactic acid is an organic acid; it builds up in muscles during hard exercise and is found in curd.
C is wrong: uric acid is an organic waste product of protein metabolism, excreted in urine; its excess causes gout.
D is wrong: methanoic (formic) acid is an organic acid found in ant stings and nettle leaves.
Exam tip: stomach = HCl (pH about 2) + pepsin; mineral acids are HCl, H₂SO₄ and HNO₃, while lactic, uric, formic and citric acids are organic.
Practice Questions
View allThe fact that the planets move around the Sun, not in circles but in ellipses, was first demonstrated by
- A.Galileo
- B.Martin Luther
- C.Johannes Kepler
- D.Copernicus
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In 1609 Kepler showed that the planets move around the Sun in elliptical orbits, with the Sun at one focus of the ellipse.
Read the full explanation →Which one of the following statements is correct?
- A.Urea is produced in liver.
- B.Urea is produced in blood.
- C.Urea is produced from digestion of starch.
- D.Urea is produced in lung and kidney.
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Liver cells turn the toxic ammonia released from the breakdown of amino acids into urea through the ornithine cycle, also called the urea cycle.
Read the full explanation →Which one of the following is the correct sequence of passage of light in a compound microscope?
- A.Condenser-Objective lens-Eyepiece-Body tube
- B.Objective lens-Condenser-Body tube-Eyepiece
- C.Condenser-Objective lens-Body tube-Eyepiece
- D.Eyepiece-Objective lens-Body tube-Mirror
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Light passes through the condenser to the specimen, is picked up by the objective lens, travels up the body tube and reaches the eye through the eyepiece.
Read the full explanation →Which one of the following statements regarding haemoglobin is correct?
- A.Haemoglobin present in RBC can carry only oxygen but not carbon dioxide.
- B.Haemoglobin of RBC can carry both oxygen and carbon dioxide.
- C.Haemoglobin of RBC can carry only carbon dioxide.
- D.Haemoglobin is only used for blood clotting and not for carrying gases.
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It binds oxygen at its iron-containing haem groups and carries some carbon dioxide on its protein chains. Each haemoglobin molecule has four polypeptide chains and four haem groups, and each haem iron can hold one oxygen molecule, forming oxyhaemoglobin in the lungs.
Read the full explanation →Which one of the following statements regarding histone proteins is correct?
- A.Histones are proteins that are present in mitochondrial membrane.
- B.Histones are proteins that are present in nucleus in association with DNA.
- C.Histones are proteins associated with lipids in the cytosol.
- D.Histones are proteins associated with carbohydrates in the cytosol.
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They are the proteins around which DNA winds to form chromatin in the nucleus of eukaryotic cells. Histones are small basic proteins, rich in the positively charged amino acids lysine and arginine, which attract the negatively charged phosphate groups of DNA.
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