Which one of the following vitamins has a role in blood clotting ?
- A.Vitamin A
- B.Vitamin D
- C.Vitamin E
- D.Vitamin K
Correct answer
Explanation
The correct answer is D, Vitamin K. Vitamin K is needed by the liver to make prothrombin and other clotting factors, without which blood does not clot properly.
The "K" comes from the German word Koagulation. Vitamin K is fat-soluble; green leafy vegetables such as spinach, cabbage and broccoli supply vitamin K1, and bacteria in the large intestine make vitamin K2. Its deficiency causes prolonged bleeding and easy bruising. Newborn babies have little vitamin K, so they are given an injection at birth to prevent bleeding. Medicines such as warfarin thin the blood by working against vitamin K.
A is wrong because vitamin A (retinol) is needed for vision and healthy skin; its lack causes night blindness. B is wrong because vitamin D helps absorb calcium for strong bones; its lack causes rickets in children. C is wrong because vitamin E is an antioxidant that protects cell membranes and is linked to fertility, not clotting.
Exam tip: fat-soluble vitamins A, D, E, K; K = coagulation (clotting), made partly by gut bacteria.
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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