Intestinal bacteria are main source of which one of the following vitamins?
- A.Vitamin E
- B.Vitamin C
- C.Vitamin B12
- D.Vitamin A
Correct answer
Explanation
The correct answer is C, Vitamin B12. Among the options it is the only vitamin made by bacteria; no plant or animal cell can make it, so bacteria, including those in the gut, are its source.
Vitamin B12, or cobalamin, contains the metal cobalt and is needed to form red blood cells and to keep nerves healthy; its lack causes pernicious anaemia. It is synthesised only by microorganisms. Bacteria living in the intestines of animals make it, which is why it reaches us through meat, eggs, milk and fish, and why strict vegetarians often need supplements. Intestinal bacteria also produce vitamin K, which helps blood to clot, and some other B vitamins such as biotin.
A is wrong because vitamin E, an antioxidant, comes from vegetable oils, nuts and green leaves. B is wrong because vitamin C comes from citrus fruits, amla and fresh vegetables and is not made by gut bacteria. D is wrong because vitamin A comes from milk, liver and the carotene in carrots and green vegetables.
Exam tip: Gut bacteria make vitamins K and B12; B12 contains cobalt and its lack causes pernicious anaemia.
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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