Class 6 Notes

Class 6 Science Notes Chapter 2 (Components of Food) – Science Book

Philoid

Philoid

— 6 min read

Science
Detailed Notes with MCQs of Chapter 2, 'Components of Food'. This is a fundamental chapter, not just for your class but also forms the basis for many questions in competitive government exams. Understanding what our food contains and why it's important is crucial.

Chapter 2: Components of Food - Detailed Notes for Exam Preparation

1. Introduction: Why Do We Need Food?

  • Food provides energy to carry out daily activities (walking, studying, playing).
  • Food helps in the growth and repair of our body tissues.
  • Food protects our body from various diseases and keeps us healthy.

2. What Do Different Food Items Contain? - Nutrients

  • The substances present in our food that provide nourishment essential for the growth and maintenance of our body are called Nutrients.
  • Our food contains six essential components:
    1. Carbohydrates
    2. Fats (Lipids)
    3. Proteins
    4. Vitamins
    5. Minerals
    6. Dietary Fibre (Roughage)
    7. Water (Often considered alongside nutrients due to its essential role)

3. Major Nutrients: Functions, Sources, and Tests

  • a) Carbohydrates:

    • Function: Primarily provide energy to our body. They are the main source of energy.
    • Types found in food: Mainly starch and sugars.
    • Sources:
      • Starch: Rice, Wheat, Maize (Corn), Bajra, Potato, Sweet Potato, Tapioca.
      • Sugars: Sugarcane, Jaggery (Gur), Honey, Ripe Fruits (like Mango, Banana, Papaya), Milk.
    • Test for Starch:
      • Take a small quantity of the food item (raw or boiled).
      • Add 2-3 drops of dilute Iodine solution.
      • Observation: A blue-black colour indicates the presence of starch.

  • b) Fats (Lipids):

    • Function: Also provide energy. In fact, fats provide more energy compared to the same amount of carbohydrates. They also help keep the body warm and protect organs.
    • Sources:
      • Plant Sources: Groundnut oil, Mustard oil, Coconut oil, Sunflower oil, Soyabean oil, Nuts (Almonds, Cashews), Til (Sesame).
      • Animal Sources: Ghee, Butter, Milk, Cream, Cheese, Eggs, Meat, Fish.
    • Test for Fats:
      • Take a small quantity of the food item.
      • Wrap it in a piece of paper and crush it (take care not to tear the paper).
      • Straighten the paper and observe.
      • Observation: An oily patch on the paper that becomes translucent (allows light to pass through partially) indicates the presence of fats.

  • c) Proteins:

    • Function: Essential for the growth and repair of body tissues. Often called "Body-Building Foods". Required for making enzymes, hormones, and other body chemicals.
    • Sources:
      • Plant Sources: Pulses (Moong, Tur dal, Gram, Beans, Peas), Soyabeans, Groundnuts.
      • Animal Sources: Milk, Paneer (Cottage cheese), Cheese, Eggs, Fish, Meat.
    • Test for Proteins:
      • Take a small quantity of the food item (if solid, make a paste or powder).
      • Put it in a clean test tube, add 10 drops of water, and shake well.
      • Using a dropper, add 2 drops of Copper Sulphate solution.
      • Add 10 drops of Caustic Soda solution (Sodium Hydroxide).
      • Shake well and let it stand for a few minutes.
      • Observation: A violet colour indicates the presence of proteins.

  • d) Vitamins:

    • Function: Required in small quantities to protect our body against diseases. They also help in keeping our eyes, bones, teeth, and gums healthy.
    • Types, Sources, Functions, and Deficiency Diseases (Important for Exams):
      • Vitamin A:
        • Function: Keeps skin and eyes healthy.
        • Sources: Carrot, Papaya, Mango, Milk, Fish oil, Spinach, Pumpkin.
        • Deficiency Disease: Night Blindness (Loss of vision in dim light/darkness).
      • Vitamin B Complex (Group of vitamins):
        • Function: Essential for energy production, nerve function, formation of red blood cells.
        • Sources: Whole grains (Rice, Wheat), Liver, Meat, Eggs, Milk, Green leafy vegetables.
        • Deficiency Disease: Beriberi (Weak muscles, very little energy to work).
      • Vitamin C:
        • Function: Helps fight against many diseases, important for healthy gums and wound healing. Easily destroyed by heat during cooking.
        • Sources: Citrus fruits (Orange, Lemon, Amla), Guava, Tomato, Green chillies.
        • Deficiency Disease: Scurvy (Bleeding gums, wounds take longer to heal).
      • Vitamin D:
        • Function: Helps our body use calcium for strong bones and teeth. Our body prepares Vitamin D in the presence of sunlight.
        • Sources: Sunlight, Milk, Butter, Fish, Eggs, Liver.
        • Deficiency Disease: Rickets (Bones become soft and bent, especially in children).
      • Vitamin E: Important for skin health, acts as an antioxidant. (Sources: Nuts, seeds, vegetable oils).
      • Vitamin K: Important for blood clotting. (Sources: Green leafy vegetables like spinach, cabbage).

  • e) Minerals:

    • Function: Needed by our body in small amounts for proper growth, good health, and various bodily functions.
    • Important Minerals, Sources, and Deficiency Diseases:
      • Calcium:
        • Function: Building strong bones and teeth, blood clotting.
        • Sources: Milk, Eggs, Cheese, Green leafy vegetables.
        • Deficiency: Bone and tooth decay, weak bones.
      • Iron:
        • Function: Essential for the formation of haemoglobin in red blood cells, which carries oxygen.
        • Sources: Spinach, Apple, Liver, Jaggery, Green leafy vegetables.
        • Deficiency Disease: Anaemia (Weakness, fatigue, pale appearance).
      • Iodine:
        • Function: Essential for the production of thyroid hormones, which control metabolism.
        • Sources: Iodized salt, Seafood (Fish, Prawns), Ginger.
        • Deficiency Disease: Goitre (Swelling of the thyroid gland in the neck).
      • Phosphorus:
        • Function: Formation of bones and teeth (works with Calcium).
        • Sources: Milk, Banana, Cereals, Pulses.

4. Dietary Fibre (Roughage):

  • Function: Does not provide any nutrients to our body but is an essential component. It adds bulk to the food, helps our body get rid of undigested food, and prevents constipation.
  • Sources: Whole grains, Pulses, Potatoes, Fresh fruits, Vegetables (especially their skins and fibres).

5. Water:

  • Function: Essential for life.
    • Helps our body absorb nutrients from food.
    • Helps in throwing out wastes from the body as urine and sweat.
    • Regulates body temperature.
  • Sources: Drinking water, Milk, Tea, Juices, Water content in fruits and vegetables.

6. Balanced Diet:

  • Definition: A diet that contains all the essential nutrients (carbohydrates, fats, proteins, vitamins, minerals), along with roughage and water, in the right proportions required for the healthy functioning of the body.
  • Importance: Necessary for growth, energy, and maintenance of good health. Prevents deficiency diseases.
  • Note: The requirement for a balanced diet depends on age, gender, and the amount of physical work done. A growing child or a labourer needs more protein and energy.
  • Key Point: Eating the 'right' kind of food is not enough; it should also be cooked properly so that its nutrients are not lost.
    • Repeated washing of rice and pulses removes some vitamins and minerals.
    • Washing fruits and vegetables after cutting/peeling can wash away water-soluble vitamins (like Vitamin C and B-complex).
    • Overcooking, especially using too much water which is then thrown away, leads to loss of nutrients. Vitamin C gets easily destroyed by heat during cooking.

7. Deficiency Diseases:

  • Definition: Diseases that occur due to the lack of one or more essential nutrients in our diet over a long period.
  • Examples (already covered under Vitamins and Minerals): Night Blindness (Vit A), Beriberi (Vit B1), Scurvy (Vit C), Rickets (Vit D), Goitre (Iodine), Anaemia (Iron), Bone/Tooth decay (Calcium).
  • Protein Deficiency: Can lead to stunted growth, swelling of the face, discolouration of hair, skin diseases, and diarrhoea.
  • Protein and Carbohydrate Deficiency (Severe): If the diet is deficient in both for a long time, growth may stop completely. The person becomes very lean, thin, and weak (often referred to as Marasmus in higher studies).

8. Obesity:

  • Definition: A condition where excess fat gets accumulated in the body.
  • Cause: Eating too much fat-rich food (like fried items, sweets) and lack of physical activity.
  • Health Risks: Can lead to heart diseases, diabetes, high blood pressure, etc.

Multiple Choice Questions (MCQs)

  1. Which nutrient is primarily known as 'energy-giving food'?
    a) Proteins
    b) Vitamins
    c) Carbohydrates
    d) Minerals

  2. A blue-black colour appears when Iodine solution is added to a food item. This indicates the presence of:
    a) Fats
    b) Proteins
    c) Starch
    d) Vitamins

  3. Which Vitamin helps our body use Calcium for bones and teeth and is synthesized in the presence of sunlight?
    a) Vitamin A
    b) Vitamin B
    c) Vitamin C
    d) Vitamin D

  4. Which of the following food sources is rich in Proteins?
    a) Potato
    b) Pulses (Dal)
    c) Orange
    d) Ghee

  5. The deficiency disease 'Scurvy', characterized by bleeding gums, is caused by the lack of which vitamin?
    a) Vitamin A
    b) Vitamin B
    c) Vitamin C
    d) Vitamin K

  6. Dietary fibres, or roughage, are important because they:
    a) Provide energy
    b) Help in body growth
    c) Help get rid of undigested food
    d) Protect from diseases

  7. Anaemia, a condition causing weakness and fatigue, results from the deficiency of which mineral?
    a) Calcium
    b) Iodine
    c) Iron
    d) Phosphorus

  8. A diet containing all essential nutrients, roughage, and water in correct proportions is called:
    a) Nutrient-rich diet
    b) Balanced Diet
    c) Energy diet
    d) Protective diet

  9. Which component of food can be tested using Copper Sulphate and Caustic Soda solutions, giving a violet colour?
    a) Starch
    b) Fat
    c) Protein
    d) Sugar

  10. Goitre, the swelling of a gland in the neck region, is caused by the deficiency of:
    a) Iron
    b) Calcium
    c) Iodine
    d) Vitamin D

Answer Key for MCQs:

  1. c) Carbohydrates (Fats also give energy, but carbs are the primary source mentioned this way)
  2. c) Starch
  3. d) Vitamin D
  4. b) Pulses (Dal)
  5. c) Vitamin C
  6. c) Help get rid of undigested food
  7. c) Iron
  8. b) Balanced Diet
  9. c) Protein
  10. c) Iodine

Make sure you revise these points thoroughly. Pay special attention to the sources of nutrients, the tests used to identify them, and the deficiency diseases associated with vitamins and minerals. Good luck with your preparation!

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