Chapter 1: NUTRITION

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Components of food necessary for the body are called Nutrients. Organisms that prepare food themselves from simple substances are called Autotrophs and animals take in ready-made food made by plants are called Heterotrophs.

  • Herbivores: Animals that eat only Plants.
  • Carnivores: Animals that eat other animals.
  • Omnivores: Animals that eat both plant and animals.

Types of nutrients:

  • Carbohydrates
  •  Fats
  •  Proteins
  •  Vitamins
  •  Minerals
  •  Dietary Fibers and Water

Carbohydrates and Fats

    Carbohydrate and fats are the energy giving food. Carbohydrate give less energy than fats. Animal fats are saturated fatty acids, which are harmful for health. We should choose unsaturated fatty acids for cooking. Trans fats are unsaturated fats that damage the heart.


Proteins are body building foods. Proteins are polypeptides i.e. linear chains of amino acids linked by peptide bonds. Enzymes are proteins which perform role of biological catalysts.
Receptors are proteins which perform function related to communication systems in the body.
Collagen is the most abundant protein in animal world and
Ribulose bisphosphate Carboxylase-Oxygenase (RuBisCO) is the most abundant protein in the whole of the biosphere. Protein deficiency causeskwashiorkor and Maerasmus.

Vitamin and Minerals

Vitamin A,E,C are anti-oxidants that absorb free radicals. The vitamins and  minerals  deficiency can cause the diseases mentioned in the  table.

Table:Deficiency diseases

Vitamins or minirals Disease
Vitamin A Night blindness / Xeropthalmia
Vitamin B1 Beri beri
Vitamin C Scurvy
Vitamin D Rickets
Vitamin E Anemia / Loss of fertility
Vitamin K Bleeding
Calcium Bone and tooth decay
Iron Anemia
Iodine Goiter

Note: Mercury poisoning causes mina mata disease and cadmium poisoning causes itai-itai.

Test to Detect Iodine, Proteins and  Fats 

  1. Test for starch: IODINE TEST
    • Take small food quantity and add dilute iodine solution if it turns blue black then it has starch
    • Take small food quantity and add copper sulphate and caustic soda solution if it turns violet then it has proteins
  3. Test for fats: PAPER TEST

    • Take small food quantity and wrap it in paper and crush it. Observe oil patch in light

Dietary Fibers and Water

    Roughage or dietary fibers are present in plant products like whole grains, pulses, potatoes, fresh fruits, vegetables. Don’t have nutrients but helps to get rid of undigested food.

Human body and nutrients

Digestion is a process in which complex components of food are broken into simpler substances.
Saliva breaks down starch into sugars. Stomach secretes mucous, hydrochloric acid and digestive juices. The mucous protects the lining of the stomach, acid kills the bacteria and digestive juices break proteins into simpler substances.
Liver is the largest gland in the body. It secretes bile stored in the gall bladder, bile is important in digestion of fats. It produces cholesterol [lipoprotein].
Low density cholesterol is bad and high density cholesterol is good.

Humans can’t digest cellulose. The temperature of a human body is 35-42° Celsius.


    Starfish feeds on animals that are covered by a calcium carbonate shell. The shell is popped open and then the starfish puts its stomach out of its mouth to eat the soft animal inside. The stomach then goes back inside and then the food is slowly digested.

    Small intestine is lined with villi which help in absorption of food. Small intestine is 7.5m and large intestine is 1.5m.     In herbivores, small intestine is longer to digest cellulose. In carnivores, small intestine is smaller as meat is easily digested.


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