Nutrition, Vitamins and Deficiency Diseases: Exam Notes

The correct answer is C, because the enzyme in saliva that acts on starch is salivary amylase, also called ptyalin, and not a lipase. Amylase breaks starch into the sugar maltose; a lipase works on fat, and saliva carries no significant lipase, so the statement pairs the right action with the wrong enzyme. Option A is a correct statement, since partly digested food leaves the stomach as chyme and enters the small intestine through the pyloric opening. Option B is correct too, because the digestion of all three major nutrients is completed in the small intestine with bile from the liver and the trypsin, amylase and lipase of pancreatic juice, and absorption follows through the villi. Option D is correct, as the oesophagus carries swallowed food from the pharynx to the stomach by peristalsis.

The correct answer is C, vitamin C. Vitamin C, chemically ascorbic acid, is needed to make collagen, the protein that holds tissues together; without it the gums swell and bleed, wounds refuse to heal and the joints ache, and the disease is called scurvy. Amla, guava, citrus fruit and tomato are rich sources, and the vitamin is destroyed by heat. Option A is wrong because a shortage of vitamin A gives night blindness and xerophthalmia, disorders of the eye. Option B is wrong because a shortage of vitamin B12 gives pernicious anaemia, a disorder of the blood. Option D is wrong because a shortage of vitamin K delays the clotting of blood, since prothrombin cannot be made in the liver without it. Scurvy was the classic disease of long sea voyages before fresh fruit was carried.

The correct answer is A, thiamine. Thiamine is vitamin B1, and its shortage causes beriberi, in which the nerves and the heart are affected, giving weakness, loss of sensation in the legs and in the wet form swelling and heart failure; the disease was common where polished rice was the staple, since polishing removes the thiamine-rich outer layer. Option B is wrong because a shortage of riboflavin, vitamin B2, gives cracks at the corners of the mouth and inflammation of the tongue. Option C is wrong because a shortage of niacin, vitamin B3, gives pellagra. Option D is wrong because ascorbic acid is vitamin C, whose deficiency gives scurvy, a disease of the gums and connective tissue. Whole grain, pulses, nuts and yeast are the usual dietary sources of thiamine.

The correct answer is D, vitamin K. Vitamin K, chemically phylloquinone, is needed by the liver to make prothrombin and other clotting factors, so a shortage of it makes bleeding last longer and can cause haemorrhage in a newborn; green leafy vegetables supply it and the bacteria of the large intestine make part of our requirement. Option A is wrong because vitamin A is concerned with vision and with the health of skin and mucous membrane. Option B is wrong because vitamin C builds collagen, and although bleeding gums occur in scurvy that is a weakness of blood vessels, not a failure of clotting. Option C is wrong because vitamin E is an antioxidant that protects cell membranes and red blood cells. Newborn babies are often given a dose of vitamin K because their gut bacteria are not yet established.

The correct answer is B, vitamin B3. Vitamin B3 is niacin, also called nicotinic acid, and its shortage gives pellagra, remembered by the three Ds of dermatitis, diarrhoea and dementia, with death as a fourth if it is untreated; the disease appeared where maize was the staple, because the niacin in maize is bound and poorly absorbed. Option A is wrong because a shortage of vitamin B1, thiamine, gives beriberi. Option C is wrong because a shortage of vitamin B6, pyridoxine, gives anaemia and in severe cases convulsions. Option D is wrong because a shortage of vitamin B9, folic acid, gives megaloblastic anaemia and, in pregnancy, defects of the neural tube in the child. Niacin can also be made in the body from the amino acid tryptophan, so a diet rich in milk protects against pellagra even when niacin itself is scarce.

The correct answer is C, cobalt. Vitamin B12 is chemically cyanocobalamin, and the cobalt atom at the centre of its ring is what the name points to; it is the only vitamin that contains a metal, it is absorbed only with the help of intrinsic factor secreted by the stomach, and its shortage gives pernicious anaemia. Option A is wrong because iron sits at the centre of haem in haemoglobin and in the cytochromes, not in a vitamin. Option B is wrong because magnesium is the metal at the centre of chlorophyll in green plants. Option D is wrong because zinc is a component of many enzymes, among them carbonic anhydrase, but not of any vitamin. B12 comes only from animal foods and microbial sources.

The correct answer is A, vitamin D. Vitamin D, chemically calciferol, is needed for the absorption of calcium and phosphorus from the intestine, so a child short of it cannot mineralise growing bone; the legs bow, the wrists thicken and the chest deforms, and the disease is rickets, while the same shortage in an adult softens formed bone as osteomalacia. It is called the sunshine vitamin because the skin makes it under ultraviolet light. Option B is wrong because a shortage of vitamin E causes the breakdown of red blood cells and, in animals, sterility. Option C is wrong because a shortage of vitamin B2 gives cheilosis and glossitis. Option D is wrong because a shortage of vitamin A affects the eye. Milk, egg yolk, fish liver oil and fortified foods supply vitamin D in the diet.

The correct answer is A, retinol. Retinol is vitamin A, and it is the raw material of rhodopsin, the pigment in the rod cells of the retina that lets us see in dim light; when it is short the eye cannot adjust to darkness, which is night blindness, and a longer shortage dries the conjunctiva as xerophthalmia and can destroy the cornea. Liver, milk and egg supply it ready made, and carrot and green leafy vegetables supply beta-carotene, which the body converts. Option B is wrong because calciferol is vitamin D, whose shortage gives rickets. Option C is wrong because tocopherol is vitamin E, an antioxidant. Option D is wrong because thiamine is vitamin B1, whose shortage gives beriberi. Night blindness is among the earliest signs of a vitamin A shortage and is reversible if treated in time.

The correct answer is B, A, D, E and K. These four dissolve in fat and not in water, so they travel with dietary fat, are stored in the liver and in body fat, show their deficiency only after a long shortage, and can be toxic in excess. The B complex vitamins and vitamin C are water soluble; the body cannot store them, the surplus is passed out in urine and they are easily lost in cooking water. Options A, C and D are wrong because each of them includes B or C, or both, among the fat soluble group. A simple way to remember the four is the word DAKE, or to note that they are the vitamins a person deficient in bile or fat absorption is likely to lack.

The correct answer is B, protein. Kwashiorkor appears when a child gets enough calories but far too little protein, typically after being weaned onto a starchy gruel; the signs are swelling of the feet and face, a distended belly, thin and discoloured hair and an apathetic look, while the muscles are not severely wasted. Option A is wrong because a shortage of calories along with protein gives marasmus instead, in which the child is extremely wasted and looks old. Option C is wrong because an iron shortage gives anaemia, with pallor and tiredness. Option D is wrong because an iodine shortage gives goitre and, in a young child, cretinism. Kwashiorkor and marasmus together are called protein energy malnutrition. Pulses, milk, egg and soya are the cheap protein sources used to treat and prevent it.

The correct answer is C, iodine. Iodine is needed to make thyroxine, the hormone of the thyroid gland; when the supply is short the gland works harder and enlarges into the swelling at the front of the neck called goitre, and in an infant the same shortage stunts growth and mental development as cretinism. This is why the law requires common salt to be iodised. Option A is wrong because an iron shortage gives anaemia. Option B is wrong because a calcium shortage weakens bone and teeth and disturbs clotting and muscle action. Option D is wrong because fluorine is the mineral whose shortage gives dental caries, while its excess in drinking water gives fluorosis, mottling teeth and deforming bone. Iodine deficiency disorders are the commonest preventable cause of mental impairment in the world.

The correct answer is C, fat. A gram of fat yields about nine kilocalories, more than twice the yield of carbohydrate or protein, because its carbon chains are far less oxidised to begin with; this is also why fat is the body’s store of energy and why fatty food is called energy dense. Options A and B are wrong because carbohydrate and protein each yield about four kilocalories per gram, and protein is in any case used mainly for building and repair rather than for fuel. Option D is wrong because vitamins yield no energy at all; they are needed in milligram quantities as coenzymes and regulators, and a vitamin tablet cannot replace a meal. Water and dietary fibre likewise yield no calories, though both are necessary in the diet.