Vitamins

Transcript

0:00Introduction

Hello everyone! Let us begin with a puzzle from your own kitchen. When vegetables are boiled for a long time, they lose much of their vitamin C and their B vitamins. But their vitamin A does not go down. Same pot, same heat, same time. So why does one vitamin leave and the other one stay? Keep that puzzle in mind, because in a few minutes you will solve it yourself. Today's topic is vitamins: what they are, their two classes, and the deficiency disease of each one. Questions on them do appear in JEE chemistry, so let's begin.

0:36What is a vitamin?

So, what exactly is a vitamin? Vitamins are organic compounds that we need in our diet, but only in small amounts. Okay? We need them for specific biological functions, for normal growth and good health. Now let me ask you this. If the body needs them so much, can it not simply make them itself? For most of them the answer is no. Most vitamins cannot be made in the body, and that is exactly why they must come from our food. Right? But there are exceptions, and they are worth remembering. Vitamin D is made in the skin when sunlight falls on it, and some other vitamins are made by bacteria living in the gut. Clear? And what happens when a vitamin is missing from the diet? Its lack causes a specific deficiency disease, a particular disease for each vitamin, and we will meet every one of them today. With me?

1:28Two classes: fat-soluble and water-soluble

Now, vitamins are sorted into two classes, by what they dissolve in. The first class is the fat-soluble vitamins, and there are just four of them: A, D, E and K, nothing more. Say the four letters together once, and they will stay in your memory. Okay? Just as the name says, they are soluble in fats and oils, and insoluble in water. Right? So where does the body keep them? They are stored in the liver and in adipose tissue, and the brackets tell you that adipose simply means fat-storing. Got it? The second class is water-soluble: the whole B group, and vitamin C as well. Now think. These dissolve in water. So if you take in more than the body needs, where does the extra go? Yes, exactly, it goes out in the urine. Water-soluble vitamins are readily excreted in urine and are not stored, so they must be supplied regularly in the diet. And now you can solve our kitchen puzzle. Why did the vitamin A stay in the boiled vegetables? That is correct, because vitamin A is fat-soluble, so it is insoluble in water. On long boiling, the B group and vitamin C dissolve in the cooking water, and vitamin C is also destroyed by heat and air, but vitamin A does not dissolve, so it stays in the vegetables. And that is our kitchen puzzle solved. With me?

2:50Fat-soluble vitamins: names, sources, diseases

Now let us meet each vitamin, with its chemical name, its sources, and an arrow pointing to the disease its lack causes. First comes vitamin A, called retinol. It comes from fish liver oil, carrots, butter and milk. Its lack causes xerophthalmia and night blindness. Okay? Next is vitamin D, calciferol. Its sources are sunlight, which acts on the skin as we saw, fish and egg yolk. Its lack causes rickets in children and osteomalacia in adults, as the brackets tell you. Right? Then vitamin E, tocopherol, which we get from vegetable oils. Its lack gives fragile red blood cells and muscular weakness. Clear? And finally vitamin K, phylloquinone, from green leafy vegetables. Its lack increases the blood-clotting time, so blood takes longer to clot. So link the letter K with clotting. Got it?

3:46Water-soluble vitamins: the B group and C

Now the water-soluble ones, starting with the B group. The small number written below each B is a subscript, so this first one is read as vitamin B one. Vitamin B one is thiamine, from yeast, milk, green vegetables and cereals, and its lack causes beriberi. Okay? Vitamin B two is riboflavin, from milk, egg white, liver and kidney. Its lack causes cheilosis and digestive disorders. Right? Vitamin B six is pyridoxine, from yeast, milk, egg yolk, cereals and grams, and its lack causes convulsions. With me? Then comes vitamin B twelve, cyanocobalamin, and the brackets tell you something special: it contains cobalt, a metal. It comes from meat, fish, egg and curd, and its lack causes pernicious anaemia. Clear? And vitamin C is ascorbic acid, from citrus fruits, amla and green leafy vegetables. Its lack causes scurvy, and the brackets give its sign, bleeding gums. Now, a quick check. We said water-soluble vitamins are excreted and not stored. Is that true for every single one of them? No, it is not, and this is a classic trap. Vitamin B twelve is water-soluble, yet it is stored in the body, in the liver. So when a question asks for the water-soluble vitamin that is stored, the answer is B twelve. Got it?

5:14Example 1: diseases from lack of vitamins C, D, B1 and A

Time for the first example, an easy one. Name the deficiency disease caused by the lack of vitamin C, vitamin D, vitamin B one, and vitamin A, in that order. The letters in brackets just number the four parts. Pause the video and try it first. Done? Okay, let's check. Lack of vitamin C causes scurvy. Lack of vitamin D causes rickets, and in adults, as the brackets say, osteomalacia. Right? Lack of vitamin B one causes beriberi, and lack of vitamin A causes xerophthalmia and night blindness. Four parts, four diseases, and that's it!

5:57Example 2: count conditions from fat-soluble vitamin lack

Now a harder one, which mixes both ideas. How many of these conditions are caused by lack of a fat-soluble vitamin? Xerophthalmia, rickets, scurvy, beriberi, and delayed clotting of blood. Here is a hint: first find the vitamin behind each condition, then its class. Pause the video and try it first. Done? Okay, let's check. Xerophthalmia comes from lack of vitamin A, and rickets from lack of vitamin D, and both of them are fat-soluble. Okay? Scurvy comes from lack of vitamin C, and beriberi from lack of vitamin B one, and both of them are water-soluble, so they do not count. That gives two conditions so far. So the answer is two, right? No, no, wait, that is the trap, because we have not checked the last one. Delayed clotting of blood means an increased blood-clotting time, and that comes from lack of vitamin K, okay? And vitamin K is fat-soluble! Clear? So the fat-soluble vitamins here are A, D and K, and the answer is three. Students who forget the link between vitamin K and clotting write two and lose the marks. See how knowing the two classes answers the whole question?

7:15Quick revision: A, D, E, K vs B group and C, key diseases

So, quick revision. The fat-soluble vitamins, A, D, E and K, are stored in the liver and in adipose tissue. The water-soluble vitamins, the B group and C, are excreted, so they must be supplied regularly, and B twelve is the one that is stored. And the diseases: lack of vitamin A gives night blindness, D gives rickets, K gives delayed clotting, C gives scurvy, and B one gives beriberi. Now go and try the practice problems on this page. All the best!