Students can download Class 8 Science Chapter 18 Food and Its Constituents Important Questions, KSEEB Class 8 Science Important Questions and Answers helps you to revise the complete Karnataka State Board Syllabus and to clear all their doubts, score well in final exams.
Karnataka State Syllabus Class 8 Science Important Questions Chapter 18 Food and Its Constituents
Question 1.
What is food? Why do organisms need food?
Answer:
Anything that when consumed gets digested easily and provides the necessary materials and energy to our body is called food. All organisms need food to survive, to grow, to remain healthy and to carry out various activities.
Question 2.
What happens to the food we consume eventually?
Answer:
The foods we consume become our blood and bones, brain and muscles. Food becomes our strength, stamina and our energy. Food also contributes to the physique, effectiveness and emotional stability.
Question 3.
What are the functions of food?
Answer:
Food has many functions. It provides energy for all our activities. It promotes growth, provides the necessary nutrients, supplies energy and furnishes materials for the repair of the body parts. Food protects the body against diseases.
Question 4.
What are nutrients?
Answer:
The nourishing substances present in food are called nutrients.
Question 5.
Why should we have variety in our diet?
Answer:
Our body requires different materials which are supplied through food. Different food substances supply different nutrients. A single food item cannot supply all the materials and nutrients in required proportion. Further, there are many food items which contain the same nutrients. Therefore, it is necessary to have variety in our diet.
Question 6.
Which are the three major types of nutrients?
Answer:
The three major types of nutrients are
- energy-giving nutrients
- protective nutrients
- body-building nutrients.
Question 7.
Which are the major constituents of our food?
Answer:
The major constituents of our food are carbohydrates, lipids, proteins, minerals, vitamins, roughage and water.
Question 8.
What are carbohydrates?
Answer:
A group of organic compounds consisting of carbon, hydrogen and oxygen atoms and which form an important constituent of our food are called carbohydrates.
Question 9.
Why are carbohydrates called energy-giving foods?
Answer:
Carbohydrates on digestion form glucose which is broken down in our body cells to produce energy. Carbohydrates are the principal source of energy to us. This is why carbohydrates are called energy-giving foods.
Question 10.
Explain the importance of carbohydrates in our diet.
Answer:
Sugars and starch are perfect fuels for energy generation in the body. They help to carry out physical activities efficiently and effectively. Carbohydrates in our diet ensure adequate supply of glucose to every cell. Fibres containing carbohydrates such as cellulose keep bowel movements smooth! Carbohydrates such as sugars add to the taste.
Question 11.
List four major sources of carbohydrates.
Answer:
Major sources of carbohydrates are cereals, sugar, jaggery, potato, sweet potato and some kinds of fruits.
Question 12.
What are dietary lipids? What are the elements present in lipids?
Answer:
Oils and fats which when consumed give energy to our body are called dietary lipids. Lipids are made of carbon, hydrogen and oxygen atoms.
Question 13.
What food items used in your region give lipids to the people who consume them?
Answer:
Dietary lipids can be obtained from both plant and animal sources. Animal fat is found in milk, cheese, butter, eggs, meat and fish. Vegetable oils are present in nuts, almonds, groundnut, coconut, sunflower seeds, palm oil, mustard and sesame seeds.
Question 14.
Explain the functions of lipids in our body.
OR
Why are lipids essential in our diet?
Answer:
Lipids help in brain functioning, smooth movement of joints, clotting of blood and energy production. Lipids are concentrated source of energy. Lipids also help the body to absorb and move vitamins A, D, E and K through the blood stream. Lipids also act as messengers within our body.
They are needed to maintain healthy skin and hair. As a protective barrier they control the movement of materials. Therefore, lipids are most essential component of our diet.
Question 15.
What are the consequences of excessive consumption of lipids? How can it be avoided?
Answer:
Excess lipids in diet may cause weight gain and obesity. Animal fat easily changes to cholesterol which is known to constrict the blood vessels, cause high blood pressure and heart disorders. These problems can be avoided by consuming lipids in limited quantity, avoiding fats from animal sources, doing regular exercise and maintaining physical activity.
Question 16.
Which are the two major constituents of our food that give energy to the body?
Answer:
Two major sources of energy-giving foods are carbohydrates and lipids.
Question 17.
Why do lipids give more energy than carbohydrates?
Answer:
Lipid molecules contain more atoms of carbon and hydrogen compared to carbohydrates. Hence, lipids on oxidation yield more energy than carbohydrates.
Question 18.
How are lipids digested in the body?
Answer:
Fats are insoluble in water and hence are not easily absorbed into our body. An enzyme called lipase produced by the pancreas helps to convert lipids into fatty acids and glycerol. These molecules on oxidation release energy.
Question 19.
What are proteins? What is a protein molecule made of?
Answer:
Proteins are the body-building foods in our diet. They provide materials for growth and maintenance of the body. Proteins are usually made of carbon, hydrogen, oxygen and nitrogen. Some proteins may also contain other elements like sulphur and phosphorus.
Question 20.
How do proteins get absorbed into our body?
Answer;
Proteins present in our food are broken down into simpler units called amino acids in the small intestine. Amino acids are water soluble molecules. They are absorbed into the blood in the small intestine
Question 21.
List some of the types of proteins in our body.
Answer:
Enzymes in our body are made of proteins. Haemoglobin which helps in oxygen transport is a protein. Various hormones that regulate the functions of the body are made of protein molecules. Some proteins in our body such as antibodies are protective in their function and help to fight infection.
Some proteins form parts of cells and tissues. The genetic material in the body such as DNA and RNA are also proteins. Insulin produced by the pancreas is also a protein.
Question 22.
Name the following:
- A protein involved in oxygen transport in our body.
- A protein that helps in the metabolism of carbohydrates.
- An enzyme that helps to break down proteins in our stomach.
- Proteins which lend support to tendons and ligaments.
Answer:
- A protein involved in oxygen transport is haemoglobin.
- A protein involved in the metabolism of carbohydrates is insulin.
- An enzyme that helps to break down proteins in our stomach is pepsin.
- Proteins that give support to ligaments and tendons are keratin and collagen.
Question 23.
Mention some of the enzymes present in our body and their functions.
Answer:
Enzymes increase the rate of biochemical reactions inside our body. An enzyme called pepsin plays an important role in digestion. Another enzyme called lactase breaks down the sugar present in the milk. Insulin helps in the metabolism of carbohydrates.
Haemoglobin present in our blood plays a crucial role in the transport of oxygen in our body. Some proteins like keratin and collagen provide support to tendons and ligaments.
Question 24.
What are amino acids made of?
Answer:
Most amino acid molecules are made of atoms of carbon, hydrogen, a carboxyl group (-COOH) and an amino group (-NH2).
Question 25.
How are amino acids classified?
Answer:
On the basis of the source from which get them, amino acids are classified as
- essential amino acids
- non-essential amino acids.
Question 26.
What are essential amino acids and non-essential amino acids?
Answer:
Our body needs a number of amino acids. Some are prepared in our body itself. Others are to be taken in through our food. Those amino acids that are prepared inside our body and hence need not be present in our food are called non-essential amino acids. Those amino acids which are not prepared inside our body and hence should be present in our food are called essential amino acids.
Question 27.
List the nutritional importance of proteins.
Answer:
Proteins are most essential for growth, repair and maintenance of our body. They are an essential part of enzymes, hormones, antibodies, haemoglobin, cells and tissues. They are the building blocks of our body.
Question 28.
What is the function of enzymes in our body?
Answer:
Enzymes increase the rate of biochemical reactions in our body.
Question 29.
Mention some of the major sources of dietary proteins.
Answer:
Pulses, milk, milk products, egg, meat, groundnut, fish, beans are some of the principal sources of dietary proteins.
Question 30.
What are vitamins? List the various types of vitamins required for our body.
Answer:
Organic components in food that are needed in very small amounts for growth of our body and for maintaining good health are called vitamins. Though they do not provide any energy to us, they are an essential component of our diet as they perform specific functions in our body. The various vitamins required for our body are vitamin A, vitamin B, vitamin C, vitamin D, vitamin E and vitamin K.
Question 31.
How are vitamins classified? Give examples for each.
Answer:
On the basis of solubility, vitamins are classified as
- water-soluble vitamins
- fat-soluble vitamins.
Vitamin B and vitamin C are water-soluble vitamins. Vitamin A, vitamin D, vitamin E and vitamin K are fat-soluble vitamins.
Question 32.
What are pro-vitamins? Give two examples.
Answer:
Certain substances that get converted into regular vitamins in an organism through metabolic processes are called pro-vitamins. eg: Beta-carotene is a pro-vitamin which gets converted into vitamin A in our body.
Question 33.
What is vitamin B complex?
Answer:
Vitamin B is not a single vitamin. It actually comprises of several vitamins which play an important role in cell metabolism. The entire group of B vitamins are together called vitamin B complex.
Question 34.
Name two vitamins synthesized inside our body.
Answer:
Vitamin D and vitamin K are synthesized inside our body.
Question 35.
Name the vitamin responsible for
- night vision
- preventing anaemia
- strengthening heart muscles
- clotting of blood
- regulating menstrual rhythm
- preventing rickets.
Answer:
- Vitamin responsible for night vision is vitamin A.
- Vitamin that helps to prevent anaemia is vitamin B12.
- Vitamin that strengthens heart muscles is vitamin B1
- Vitamin that helps in clotting of blood is vitamin K.
- Vitamin that regulates menstrual rhythm is vitamin E.
- Vitamin that prevents rickets is vitamin D.
Question 36.
Which vitamin is known as sunshine vitamin? Why? What are its functions?
Answer:
Vitamin D is called sunshine vitamin. This is because vitamin D is synthesized in our body when the body is exposed to sunshine. Vitamin D promotes the development of bones and teeth. It also helps in the utilization of phosphorus and calcium. It helps to maintain the health of the nervous system and functioning of heart. It prevents rickets.
Question 37.
What is night blindness? Name the vitamin whose deficiency in our body causes night blindness.
Answer:
Inability of a person to see clearly in dim light is known as night blindness. It is caused by the deficiency of vitamin A.
Question 38.
List some natural sources of vitamin A.
Answer:
Vitamin A is present in fish liver oil, liver, milk, carrots, greens, papaya, yellow vegetables and dairy products.
Question 39.
What are the functions of vitamin C in our body? Suggest some natural sources of vitamin C.
Answer:
Vitamin C helps in the absorption of iron, some proteins and folic acid. It prevents oxidation of other vitamins. It plays an important role in preventing internal bleeding. It strengthens blood vessels, maintains the strength of bones and teeth. It also prevents infections, cold, fatigue and stress. It also helps to heal wounds.
Question 40.
What are dietary minerals? Give examples.
Answer:
Chemical elements, other than carbon, oxygen, hydrogen and nitrogen, that should be present in our food are called dietary minerals. Dietary minerals include sodium, potassium, calcium, phosphorus, iron, iodine, zinc, etc.
Question 41.
Why are dietary minerals essential to our body?
Answer:
Minerals have no energy value. However, they perform some very important functions in our body. Therefore, dietary minerals are essential to our body.
Question 42.
List some of the dietary sources of calcium.
Answer:
Dairy products, soyabeans, tapioca, ragi, fish, sunflower seeds and legumes are some of the principal sources of dietary calcium.
Question 43.
Write any three functions of calcium in our body.
Answer:
Calcium helps to build bones and teeth. It helps in the proper functioning of muscles, heart and nerves. It relieves pain and cramps. It helps in clotting of blood.
Question 44.
Mention the functions of sodium in our body.
Answer:
Sodium helps to control blood pressure, regulates the function of muscles and nerves.
Question 45.
List the functions of phosphorus in our body.
Answer:
Phosphorus is required for the formation of bones and teeth. It is involved in metabolism of carbohydrates, fats and proteins. Phosphorus is abundant in milk, milk products, whole grains, etc.
Question 46.
State one dietary importance of iron. List some of the natural sources of iron to our body.
Answer:
Iron is essential for the formation of haemoglobin in the red blood cells. Dietary sources of iron are liver,oat meal,oysters, egg, meat, nuts, beans, wheat germ,apple, banana and other green vegetables.
Question 47.
Name the mineral required for proper functioning of thyroid gland. What are its other functions?
Answer:
Iodine is the mineral required for proper functioning of thyroid gland. Iodine helps to prevent goitre, burn body fat, convert beta-carotene into vitamin A, regulate energy production in the body and maintain the health of hair, nail, skin and teeth.
Question 48.
List some of the sources of iodine in our diet.
Answer:
Dietary iodine can be obtained from sea foods, iodized salt and green vegetables.
Question 49.
What is the function of iodine in our body?
Answer:
Iodine helps in the secretion of thyroxine from thyroid gland. It prevents goitre. It helps to burn fat; converts beta-carotene into vitamin A; regulates energy production in our body and maintains hair, nails, skin and teeth.
Question 50.
What is the function of zinc in our body?
Answer:
Zinc in our diet helps to reduce cholesterol deposits. It promotes synthesis of enzymes and insulin. It supports the metabolism of carbohydrates. It also facilitates the proper functioning of prostate glands.
Question 51.
List some dietary sources of zinc mineral.
Answer:
Zinc is present in eggs, cheese, beef, pork, wheat germ, brewer’s yeast and pumpkin seeds.
Question 52.
What is the importance of potassium in our body? List some sources of potassium in our diet.
Answer:
Potassium helps to regulate fluid balance in our body. It is also needed for the proper functioning of nerves and muscles. Peanuts, bananas, green beans, mushrooms and oranges are a few good sources of potassium.
Question 53.
Name two ingredients that must be present in our food although they have no nutritional significance.
Answer:
Roughage and water must form an integral part of our food although they have no nutritional value.
Question 54.
What is roughage? How does eating plenty of roughage help to prevent constipation?
Answer:
The fibrous material present in our food is called roughage. Roughage provides bulk to the food and helps in the movement of food through alimentary canal. This prevents constipation.
Question 55.
List some sources of roughages in our diet.
OR
Make a list of food items that are rich in dietary fibres.
Answer:
Whole grains, fruits, vegetables, greens are some excellent sources of roughage.
Question 56.
What is constipation? How can it be prevented?
Answer:
A condition in which there is difficulty in emptying the bowels, usually associated with hardened faeces, is known as constipation. Constipation can be prevented by drinking plenty of water and by consuming lot of dietary fibre.
Question 57.
Explain the importance of water in our diet.
OR
Why is water essential to our body?
Answer:
Water constitutes about 55-75 percent of our body mass. The prominent constituent of blood, digestive juices, urine and perspiration is water. We need fresh supplies of water to make up for losses from lungs, skin, urine and faeces. Water helps to maintain the health of every cell in the body. It keeps the blood thin enough to flow through blood vessels.
It helps to eliminate the wastes and excess materials. Water regulates body temperature through sweating. It keeps mucous membranes, lungs and mouth in moist condition. Water helps digestion and prevents constipation.
It improves the texture of the skin and its appearance. It helps to earn nutrients and oxygen to the cells. It serves as a shock absorber inside the eyes, spinal cord and in the amniotic sac surrounding the foetus in pregnancy.
Question 58.
What is dehydration? What are its common causes?
Answer:
The condition resulting from excessive loss of water and salts essential for the normal functioning of the body is called dehydration. The common causes of dehydration are diarrhoea, vomiting or both.
Question 59.
List the symptoms of dehydration.
Answer:
Symptoms of dehydration include headaches, lethargy, dry or cracked lips, dark coloured urine and physical weakness.
Question 60.
What are the risks involved in not taking adequate quantity of water regularly?
Answer:
Lack of adequate quantity of water in the body increases the risk of tiredness, stress, dehydration, kidney stones, urinary tract infections and even kidney failure.
Question 61.
What is ORS? How is it prepared?
Answer:
ORS is the abbreviation for Oral Rehydration Solution. It is prepared by dissolving one teaspoonful table salt and six teaspoonfuls of common sugar to 1 litre of potable water.
Question 62.
Why do some people suffer from nutritional deficiencies despite having enough food to eat?
Answer:
Some people may consume stomach full of food but still suffer from nutritional deficiencies. This is because they may not be providing all the essential nutrients in right proportion to their body through food.
Question 63.
What is balanced diet? List all the major classes of ingredients that should be present in balanced diet.
Answer:
A diet that contains all the essential nutrients in correct proportions is called balanced diet. Balanced diet should contain carbohydrates, lipids, proteins, minerals, vitamins, water and fibres in proper proportion.
Question 64.
Why should we take balanced diet?
Answer:
Our body needs various nutrients in varying proportions. Taking balanced diet will prevent many nutritional disorders, keep away diseases and keep our body healthy and active. Therefore, w’e must consume balanced diet.
Question 65.
Describe a simple test for starch.
Answer:
Take a small quantity of the material to be tested. Crush it well and put it into a test tube containing water. Add a few drops of iodine solution to the test tube and observe the colour. The appearance of blue-black colour indicates the presence of starch.
Question 66.
What is Benedict’s reagent? What is it used for?
Answer:
Benedict’s reagent is a mixture of sodium hydroxide, tartaric acid and copper sulphate. Benedict’s reagent is used to test the presence of simple sugars.
Question 67.
Describe Benedict’s test for sugar (glucose).
Answer:
Take about 5 ml of the solution to be tested in a test tube. Add about 5-6 drops of Benedict’s reagent and heat for about two minutes. Benedict’s reagent is a blue-coloured solution. If the colour of the solution remains blue, we can conclude that the solution does not contain glucose.
A change in colour of the solution indicates the presence of glucose in it. If glucose is present, we see a progressive change in colour from blue, green, yellow, orange, red and then brick red.
Question 68.
What is Biuret solution? What is it used for?
Answer:
A bluish solution containing sodium hydroxide and a small amount of copper sulphate is called Biuret solution. It is used to lest the presence of proteins.
Question 69.
Describe Biuret test for proteins.
Answer:
Take about 5 ml of the solution to be tested in a test tube. Add 5-6 drops of Biuret solution. Wait for a while. Do not heat. A change in colour from blue to pink indicates the presence of protein matter in the solution.
Question 70.
What is emulsion? Give an example.
Answer:
A mixture of two or more liquids which do not mix with one another is called emulsion. Oil and water do not mix with each other and hence their mixture forms an emulsion.
Question 71.
Describe emulsion test for fats and oils.
OR
A beaker contains a thick liquid. How do you test whether it is a lipid?
Answer:
Take a small quantity of tap water in a test tube. Pour a given sample of the liquid to be tested into it. If one of the two liquids settles down in the test tube in two distinct layers, then, we may say that the liquid is a fat or oil.
Question 72.
How do you test whether groundnuts contain oil or not?
Answer:
Crush a few groundnuts. Put it in a test tube. Add a small amount of ethyl alcohol to it. Shake well. Heat the test tube carefully on a water bath. Avoid direct heating. When the substance dissolves in alcohol, filter or dilute until a clear liquid is obtained. Add this solution to water taken in another test tube. A whitish suspension indicates the presence of fat or oil.
Question 73.
Name the following
- A protein which functions as a hormone.
- A carbohydrate found in dietary fibres.
- A protein that carries oxygen to the tissue cells.
- A vitamin which is important for normal vision.
- A mineral necessary for functioning of the thyroid glands.
- A vitamin required for clotting of blood.
- A vitamin necessary for the formation of bones and teeth.
- A vitamin required for the formation of RBC.
Answer:
- Insulin.
- Cellulose.
- Haemoglobin.
- Vitamin A.
- Iodine.
- Vitamin K.
- Vitamin D.
- Vitamin B12.
Multiple Choice Question
Question 1.
The major metal present in the bones is made up of sodium
(a) Sodium
(b) iron
(c) calcium
(d) phosphorus
Answer:
(c) calcium
Question 2.
Sunlight is the major source of
(a) Vitamin A
(b) Vitamin B
(c) Vitamin C
(d) Vitamin D
Answer:
(d) Vitamin D
Question 3.
Children are fond of eating too much of bakery products and chocolates. Elders advise them to eat vegetables and not to keep aside curry leaves while eating food items. This shows the importance of
(a) carbohydrates
(b) factor
(c) proteins
(d) lipids
Answer:
(b) factor
Question 4.
Foods that are rich in fats and carbohydrates are
(a) Energy-giving foods
(b) Body-building foods
(e) Protective foods
(d) Toxic foods
Answer:
(a) Energy-giving foods
Question 5.
You should limit all of the following in your diet, except
(a) Alcohol
(b) Sugar and Salts
(c) Saturated fats
(d) Fibres
Answer:
(d) Fibres
Question 6.
Night-Blindness is caused due to deficiency of
(a) Vitamin A
(b) Vitamin B
(c) Vitamin C
(d) Vitamin K
Answer:
(a) Vitamin A
Question 7.
Carbohydrates, lipids, and proteins all contain carbon, hydrogen, and oxygen. Which one also contains nitrogen?
(a) Carbohydrates
(b) Lipids
(c) Proteins
(d) none of the above
Answer:
(c) Proteins
Question 8.
Lipids are supplied in large quantities in the diet by
(a) cereals, fruits, vegetables, and breads.
(b) fats, oils, meats, and nuts.
(c) deep green and orange vegetables.
(d) green pepper, broccoli, cantaloupe, and citrus fruits.
Answer:
(b) fats, oils, meats, and nuts.
Question 9.
The building blocks of proteins are
(a) amino acids.
(b) fatty acids.
(c) glucose units
(d) saliva
Answer:
(a) amino acids.
Question 10.
A green leaf that has fallen down from a plant is taken and kept in water for sometime and then taken out. It is then dipped in spirit and iodine-solution. The leaf turns bluish indicating the presence of
(a) proteins
(b) oil
(c) starch
(d) fibre
Answer:
(c) starch
Question 11.
Green and leafy vegetables are a rich source of
(a) fats
(b) vitamin C
(c) vitamin B12
(d) carbohydrates
Answer:
(b) vitamin C
Question 12.
Which of the following constituents of food serve as instant sources of energy?
(a) fats
(b) carbohydrates
(c) proteins
(d) dietary fibres
Answer:
(b) carbohydrates
Question 13.
Which of the following is a messenger protein in our body?
(a) insulin
(b) haemoglobin
(c) keratin
(d) collagen
Answer:
(a) insulin
Question 14.
Amino acids are the building blocks of
(a) carbohydrates
(b) fats
(c) oils
(d) proteins
Answer:
(d) proteins
Question 15.
Which of the following is a function of Vitamin K?
Answer:
(a) formation of bones and teeth
(b) formation of RBC
(c) clotting of blood
(d) normal vision
Answer:
(c) clotting of blood
Fill In The Blanks
- Emulsion test is conducted to detect oils/fats
- Fat soluble vitamins are A, D, E and K
- Amino acids contain the elements carbon, hydrogen, oxygen and nitrogen
- The haemoglobin responsible for transportation of oxygen to the different parts of the body is iron
- Biuret solution contains sodium hydroxide and copper sulphate
- An amino acid molecule contains a -COOH group and -NH2 group
- The dietary fibre is also called roughage
- The vitamin whose deficiency causes rickets is vitamin D
Match The Following
| A | B |
| 1. Haemoglobin | (a) Prevents night blindness |
| 2. Vitamin C | (b) Clotting of blood |
| 3. Vitamin A | (c) Heals wounds |
| 4. Vitamin K | (d) Oxygen carrier |
| (e) Helps in digestion | |
| (f) Improves immunity system | |
| (g) Develops muscles |
Answer:
1 – d, 2 – c, 3 – a, 4 – b.