FOOD AND ITS CONSTITUESNTS

SCIENCE FOR GRADE 7 CHAPTER 1

OBJECTIVES

Recognize constituents of foodAppreciate importance of balanced dietExplain the meaning and importance of carbohydrates,

proteins and lipidsCultivate healthy food habits

What is a balanced diet?

Healthy food includes carbohydrates, proteins, minerals, lipids, vitamins and roughage. When these are present in required quantity to provide all the essential nutrients, it is termed as balanced diet.

NOTE: Besides food, water is also very essential as it helps our body to absorb nutrients from food. It also helps in discharging wastes from body as urine and sweat.

What are carbohydrates?

Carbohydrates are commonly called sugar or saccharides. They are made up of carbon, oxygen and hydrogen. Hydrogen and oxygen and present in the ratio 2:1.Example: Bread, Pasta, Sugar.

Foods with high carbohydrate are often highly processed or refined foods made from plants, including sweets, cookies and candy, table sugar, honey, soft drinks, breads and crackers, jams and fruit products, pastas and breakfast cereals.

MonosaccharidesGlucose is simple suger unit(molecule) Fruits contains fructoseThey contain 6 carbons, hence hexoseRibose and Deoxyribose contain 5 carbon, hence pentosesThey are sweet to taste and soluble in water

DisaccharidesMilk contains lactose Sugar added to milk is sucroseMade of two units of monosaccharides

Oligosaccharides Two to ten units of monosaccharides Linkage of two monosaccharides is called glysodic bond Plants have cell membrane and cell wall made of cellulose Cellulose made of more than 10 units of monosaccharides,hence called

polysaccharide

Glucose is simple sugar unitWhat do fruits contain? They contain fructoseGlucose and fructose are monosaccharidesAll theses contain 6 carbon, hence hexose

sugarMonosaccharides are water soluble and sweet

to taste

NOTE:

Importance of carbohydrates

Carbohydrates are the body’s main source of fuel. Carbohydrates are easily used by the body for energy. All of the tissues and cells in our body can use glucose for energy. Carbohydrates are needed for the central nervous system, the kidneys, the

brain, the muscles (including the heart) to function properly. Carbohydrates can be stored in the muscles and liver and later used for

energy. Carbohydrates are important in intestinal health and waste elimination. Carbohydrates are mainly found in starchy foods (like grain and potatoes),

fruits, milk, and yogurt. Other foods like vegetables, beans, nuts, seeds and cottage cheese contain carbohydrates, but in lesser amounts.

https://www.youtube.com/watch?v=lMxFLANGbKM

What are protiens?

Proteins are made of amino acids. Amino acids contain carbon, hydrogen, oxygen and nitrogen. There are 20 different types of amino acids. These amino acids are linked by peptide bonds.

Amino acids can be placed in the category of either essential or non-essential. Essential amino acids are those that are "essential" in the diet. In other words, we cannot create them through our own metabolism. Therefore, we need to obtain them through foods containing them.(e.g., muscle tissue, etc.)Non-essential amino acids are those which can be produced from other amino acids and substances in the diet and metabolism. During times of need, the metabolism can shift into producing the amino acids that it requires for synthesizing proteins essential to our survival.

Importance of protiens

Enable growth of muscle, organs and blood volume Repair body tissue Aid development of the immune system Affect digestion and metabolism Provide energy Transport molecules around the body, for example in haemoglobin in the

blood

https://www.youtube.com/watch?v=3-kljMSQ0rM

What are lipids?

Lipids are a group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E, and K), monoglycerides, diglycerides, triglycerides, phospholipids, and others. The main biological functions of lipids include storing energy, signaling, and acting as structural components of cell membranes. Lipids have applications in the cosmetic and food industries as well as in nanotechnology.

Importance of lipids?

Lipids (in the form of fats) form an important component of our diet. Also, food is stored in our body in the form of fats (which are lipids). Fats provide slow and long lasting energy. Lipids as phospho-lipids are found in plasma membranes and other organelle membranes of all the cells. Lipids as lipoproteins and lipopolysaccharides are found in the plasma membranes of Bacteria. Wax which is a Lipid. It is of various types: Cerumen (Ear wax): It is found in the human ear to protect the entry of bacteria and insects and also to amplify sound. Lanolin (Wool Wax): It is found in the wool of animals to protect them gainst the ravages of climate and the environment. Beewax is produced by bees and it us used for making candles. 

Points to remember

We need food for energy and growth Food is obtained from plants and animals A balanced diet needs right amount of carbohydrates, proteins and minerals Balanced diet is necessary for a healthy mind and a healthy body Avoid junk food. Select your food wisely Drink at least 2 ltrs of water everyday

Solved Exercise:

Q.1 Four alternatives are given under each question. Choose the correct option.

1. One of the following is not the energy source for our body.(i) Carbohydrates (ii) Proteins (iii) Fats (iv) Roughage2. The number of molecules of simple sugars in oligosaccharide is(i) 3 (ii) 2-10 (iii) more then 10 (iv) 23. In our body the principle energy source is(i) Glucose (ii) maltose (iii) starch (iv) glycogen

Answers: 1.(iii) 2.(ii) 3.(iv)

Answer the following question1.Name any three constituents of our food?(i)Proteins(ii)Carbohydrates(iii)Lipids

2.Which of the two constituents provide energy to our body?(i)Carbohydrates(ii)Roughage

3.What are carbohydrates? Give two examplesCarbohydrates are commonly called sugar or saccharides. They are made up of carbon, oxygen and hydrogen. Hydrogen and oxygen and present in the ratio 2:1.Example: Bread, Pasta, Sugar.

4.Write two differences between monosaccharides and oligosaccharides?Refer slide 7

5. Mention importance of(a)Carbohydrtaes(b)Protiens (c)Lipids Please refer the slides

6.Difference between amino acids and proteins?Proteins are made of amino acids.

7.What are proteins? Give two example.Proteins are an important constituent of balanced diet of a human being. Protein is made of amino acids. Example milk, green vegetables