The protein casein is present in milk.

Autotrophs synthesise their own food by the process of photosynthesis.

Proteins help in the formation of hair and nails in humans.

Vitamin A is important for good vision.

Glucose is a monosaccharide sugar, while the rest of the options are disachharide sugars. 

Fats act as an insulator and prevent the loss of heat from the animal body.

Amla, orange and lemon are citrus fruits. They are a rich source of vitamin C. 

Vitamins are major components of our food. They strengthen our body to fight against diseases.

Calcium is a major component of our bones and teeth. Iron is present as haemoglobin in blood and iodine is required for the regular body metabolism. Mercury is poisonous for our health and can lead to death even if taken in small amount. 

Our teeth and bones are basically formed from the compounds of calcium, the deficiency of which leads to their decay.

Deficiency of proteins in the diet for a long time results in swelling of face and neck, undergrowth of the body, etc. This is because proteins are the building blocks of the body and should be taken in sufficient amounts. 

Goitre is a disease in which the thyroid gland in the body does not work properly. This happens due to low intake of iodine in diet. 

Anaemia refers to low haemoglobin/blood level in the body which occurs when we do not take enough iron in our diet. This is because iron forms haemoglobin, which is a major component of our blood. 

The presence of any nutrient can be tested and confirmed by particular tests, e.g. presence of proteins can be tested by using copper sulphate and caustic soda. Oily patch on paper, when a food product is kept over it, confirms the presence of fats. The addition of iodine turns the starchy food to blue-black. 

Fruits and vegetables are a major source of vitamins and minerals. Washing and peeling more than required result in the loss of these two nutrients from them.