Class 6 Science Notes Chapter 2 (Chapter 2) – Examplar Problem Book
Alright class, let's dive into Chapter 2, 'Components of Food', from your Science Exemplar book. This chapter is crucial for understanding nutrition and forms the basis for many questions in competitive exams. Pay close attention!
Chapter 2: Components of Food - Detailed Notes for Government Exams
(Based on NCERT Class 6 Science Exemplar)
1. Introduction: Why Do We Need Food?
Food provides energy for activities, materials for growth, and substances to maintain bodily functions and protect against diseases. The useful substances in food are called Nutrients.
2. Major Nutrients in Our Food:
Our food contains six main types of essential components:
* Carbohydrates
* Fats
* Proteins
* Vitamins
* Minerals
* Dietary Fibres (Roughage)
* Water
3. Carbohydrates:
* Function: Main energy-giving compounds. Provide quick energy to the body.
* Forms: Found as starch and sugars.
* Sources:
* Starch: Rice, wheat, maize (corn), potato, sweet potato, tapioca.
* Sugars: Sugarcane, jaggery (gur), honey, ripe fruits (like banana, mango), milk.
* Test for Starch:
* Take a small quantity of the food item (or its paste).
* Add 2-3 drops of dilute Iodine solution.
* Observation: A blue-black colour indicates the presence of starch.
4. Fats (Lipids):
* Function: Also provide energy – significantly more energy than the same amount of carbohydrates. Store energy for future use, insulate the body, and protect organs.
* Sources:
* Plant Sources: Groundnuts, nuts (almonds, cashews), til (sesame), vegetable oils (mustard oil, coconut oil, soybean oil, sunflower oil).
* Animal Sources: Meat, fish, eggs, milk, butter, ghee, cream.
* Test for Fats:
* Take a small quantity of the food item.
* Wrap it in a piece of paper and crush it (careful 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. (Note: Water might also wet the paper, but it dries up; the oily patch doesn't).
5. Proteins:
* Function: Needed for growth and repair of body tissues. Often called "Body-Building Foods". Essential for making enzymes, hormones, and other body chemicals.
* Sources:
* Plant Sources: Pulses (moong, tur/arhar, masoor, peas, beans, gram), soybeans (richest plant source).
* Animal Sources: Meat, fish, eggs, milk, paneer (cottage cheese).
* Test for Protein:
* Take a small quantity of the food item. If solid, make a paste or powder.
* Put it in a test tube, add 10 drops of water, and shake well.
* Add 2 drops of Copper Sulphate solution.
* Add 10 drops of Caustic Soda (Sodium Hydroxide) solution.
* Shake well and let it stand for a few minutes.
* Observation: A violet colour indicates the presence of proteins.
6. Vitamins:
* Function: Required in small quantities. Help in protecting our body against diseases. Essential for maintaining healthy eyes, bones, teeth, gums, and skin. They do not provide energy but help in utilizing other nutrients.
* Types, Sources, and Deficiency Diseases:
* Vitamin A: Keeps skin and eyes healthy. Deficiency causes Night Blindness (poor vision in dim light). Sources: Carrots, papaya, mango, pumpkin, spinach, milk, fish oil, egg yolk.
* Vitamin B Complex: Group of vitamins essential for energy production, nerve function, formation of red blood cells. Deficiency causes Beriberi (weak muscles, low energy). Sources: Whole grains, unpolished rice, milk, eggs, meat, fish, green leafy vegetables.
* Vitamin C: Helps fight diseases, heals wounds, maintains healthy gums and skin. Deficiency causes Scurvy (bleeding gums, swelling of joints, wounds take longer to heal). Sources: Citrus fruits (amla, orange, lemon), guava, tomato, green chillies. Note: Easily destroyed by heat during cooking.
* Vitamin D: Helps the body absorb and use calcium for strong bones and teeth. Deficiency causes Rickets (bones become soft and bent) in children. Sources: Sunlight exposure (body makes Vitamin D), milk, fish, eggs, butter, cod liver oil.
* Vitamin E: Acts as an antioxidant. Sources: Vegetable oils, nuts, seeds, green leafy vegetables.
* Vitamin K: Essential for blood clotting. Deficiency can lead to excessive bleeding. Sources: Green leafy vegetables (spinach, cabbage, broccoli), cauliflower.
7. Minerals:
* Function: Needed in small amounts for proper growth, development, and maintaining good health. Each mineral has specific functions.
* Important Minerals, Functions, Sources, and Deficiency Diseases:
* Calcium: For building strong bones and teeth, blood clotting, muscle function. Deficiency leads to weak bones, tooth decay. Sources: Milk, cheese, yoghurt, eggs, green leafy vegetables, ragi.
* Phosphorus: For formation of bones and teeth, energy metabolism. Sources: Milk, cereals, pulses, fish, meat, eggs.
* Iron: Essential component of haemoglobin in red blood cells, which carries oxygen. Deficiency causes Anaemia (weakness, fatigue, pale skin). Sources: Spinach, green leafy vegetables, jaggery, apples, liver, meat, dates.
* Iodine: Needed for the production of thyroid hormones (regulate growth and metabolism). Deficiency causes Goitre (swelling of the thyroid gland in the neck). Sources: Iodised salt, seafood, ginger, spinach.
* Sodium & Potassium: Maintain fluid balance, nerve function. Sources: Common salt, fruits, vegetables.
8. Dietary Fibre (Roughage):
* Function: Does not provide nutrients but adds bulk to the food. Helps in the movement of food through the digestive tract and prevents constipation by aiding the removal of undigested waste.
* Sources: Whole grains (atta, oats, daliya), pulses, potatoes, fresh fruits (especially with skin), vegetables (like carrots, cabbage, beans).
9. Water:
* Function: Essential for life. Helps absorb nutrients from food, transports substances within the body, regulates body temperature (through sweating), and helps remove waste products (urine, sweat). Makes up about 70% of our body weight.
* Sources: Drinking water, beverages (milk, juice, tea), fruits (watermelon), vegetables (cucumber, tomato).
10. Balanced Diet:
* Definition: A diet that provides all the essential nutrients (carbohydrates, fats, proteins, vitamins, minerals) in the right quantities, along with adequate amounts of roughage and water, necessary for maintaining good health, growth, and energy levels.
* Importance: Prevents deficiency diseases and promotes overall well-being.
* Factors Affecting Requirement: Needs vary based on age (children need more protein), gender, physical activity level (labourers need more energy), and health status (e.g., pregnancy).
* Note: A balanced diet is not the same for everyone.
11. Deficiency Diseases:
* Definition: Diseases caused by the lack of specific nutrients in the diet over a prolonged period.
* Examples: (Refer to Vitamins and Minerals sections for details on Night Blindness, Beriberi, Scurvy, Rickets, Anaemia, Goitre).
* Protein Deficiency: Can cause stunted growth, swelling of the face, skin diseases, diarrhoea, discolouration of hair. Severe protein deficiency leads to Kwashiorkor.
* Protein and Carbohydrate (Energy) Deficiency: If the diet is deficient in both proteins and carbohydrates for a long time, growth may stop completely. The person becomes very lean, thin, and weak. This condition is known as Marasmus.
12. Cooking and Nutrient Preservation:
* Cooking improves taste and digestibility but can lead to nutrient loss.
* Vitamin C is easily destroyed by heat.
* Washing vegetables after cutting/peeling removes water-soluble vitamins (B, C) and minerals.
* Repeated washing of rice and pulses removes some vitamins and minerals.
* Using excess water for cooking and discarding it leads to loss of nutrients.
* Recommendations: Avoid overcooking, steam or pressure cook, cook in minimal water, wash vegetables before cutting.
13. Obesity:
* Cause: Consuming excessive amounts of fat-rich foods (and overall calories) than required by the body, leading to the deposition of excess fat.
* Health Risk: Obesity increases the risk of heart disease, diabetes, and other health problems.
Multiple Choice Questions (MCQs):
-
Which nutrient test involves using Copper Sulphate and Caustic Soda solutions?
(a) Test for Starch
(b) Test for Protein
(c) Test for Fats
(d) Test for Vitamin C -
Rickets, a condition where bones become soft and bent, is caused by the deficiency of:
(a) Vitamin A
(b) Iron
(c) Vitamin C
(d) Vitamin D -
Which of the following provides the most energy per gram?
(a) Carbohydrates
(b) Proteins
(c) Fats
(d) Vitamins -
Dietary fibres (Roughage) are important because they:
(a) Provide energy
(b) Help in body growth
(c) Help get rid of undigested food
(d) Protect against diseases -
Anaemia is caused due to the deficiency of which mineral essential for haemoglobin formation?
(a) Calcium
(b) Iodine
(c) Iron
(d) Phosphorus -
Which of these food items is a rich source of both Vitamin A and Vitamin C?
(a) Rice
(b) Milk
(c) Mango
(d) Pulses -
A balanced diet must contain adequate amounts of:
(a) Only carbohydrates and fats
(b) Only proteins and vitamins
(c) All essential nutrients, roughage, and water
(d) Only minerals and water -
The disease Scurvy, characterized by bleeding gums, is caused by the deficiency of:
(a) Vitamin B
(b) Vitamin C
(c) Vitamin K
(d) Calcium -
Goitre is primarily associated with the deficiency of:
(a) Iron
(b) Iodine
(c) Vitamin A
(d) Calcium -
Which cooking practice can lead to the loss of Vitamin C?
(a) Steaming vegetables
(b) Eating raw fruits
(c) Boiling vegetables for a long time in excess water
(d) Washing vegetables before cutting
Answer Key for MCQs:
- (b) Test for Protein
- (d) Vitamin D
- (c) Fats
- (c) Help get rid of undigested food
- (c) Iron
- (c) Mango (Good source of Vit A, also contains Vit C)
- (c) All essential nutrients, roughage, and water
- (b) Vitamin C
- (b) Iodine
- (c) Boiling vegetables for a long time in excess water
Remember to link the nutrients to their functions, sources, tests, and deficiency diseases. Understanding the concept of a balanced diet is also key. Keep revising!