CBSE Class 4 Science – 5. Food and Digestion (Notes)

Food – Those things which we eat to get energy are called food.       

Ex-Bread, Rice, Pulses, Snacks etc

 

 

Food nutrient –The components of food are called nutrients.

Nutrients provide nourishment essential for the maintenance of life and for growth.

 

There are five major nutrients except water & roughage.

 

 

Nutrients	Function	Source
Carbohydrate (Energy giving)	To do work	Cereals, Sugar, Potato, fruits, bread
Fats Quick energy giving nutrients (twice then carbohydrate)	Do work and keep body warm	Milk, Cream, Ghee, Butter, Cheese, Meat, Oil, Nut
Protein Body building nutrients	Growth and repair of cells	Meat, Egg, Milk, Cheese, Pulses, Soya beans, Fish
Vitamins- Protective nutrients	Protective & Resistance from diseases	Green leafy vegetables, Fruits, Fish, Milk, Eggs, Carrot
Minerals– Protective & building nutrients Iron, Calcium, Iodine	Growth & development of body, boon, teeth	Fruit, Vegetables, Milk, Cheese, Egg

Note: – No single food contains all the nutrients in the desired quantities so we need to eat balance diet for proper functioning of body.

 

Carbohydrates -The Nutrient which provides energy for the body is called Carbohydrates.

It is called energy giving food.

We get carbohydrate in two form like sugar and starch.

 

Proteins – The Nutrient which helps us to growth, building of muscles, maintenance and repairs the damage parts of our body is called Proteins.

Notes: Proteins are known as body building food.

 

How are proteins and carbohydrates useful?

Proteins and carbohydrates are useful for us due to following reasons-

Proteins and carbohydrates give more energy to do work.

Proteins are important for the maintenance and repair of the body.

Children require more protein for their growth.

 

Fat – The energy product which provides more energy than carbohydrates is called fats.  

Fats are also energy producing food.

Fats keep our body warm and protect the delicate organs inside the body.

They act as reserve of energy when carbohydrates are not available.

It helps to keep body warm.

Note:

Excess of fat in our diet gets stored in the body and become fat.

Too much of fats is not good for our health.

         

Vitamins – Those Nutrients which help of our body to fight against diseases are called Vitamins.

 

Minerals – Essential nutrients that are needed in small amounts to keep you healthy are called minerals. Ex- calcium, iron, sodium, potassium etc

The body needs many minerals such as calcium, iron, sodium, potassium and many others.

We need all minerals in to stay healthy in desired quantity.

Our body needs calcium to maintain healthy bones and teeth.

Calcium we get from milk, milk products etc.

Iron is also a mineral which helps in the formation of blood.

Iron rich food includes red meats, dried fruits and green leafy vegetables.

Milk is called a completer food as it provides all types of nutrients.

Note:

Vitamins and minerals are called protective food.

Lack of vitamins and minerals lead to deficiency diseases.

 

Roughage -The fibre present in some food items like fruits and vegetables are called roughage.

Source- fruits, vegetables and the outer covering of cereals and pulses.

Roughage helps in moving the food along the digestive tract as it adds bulk to the food.

Roughage is the indigestible portion of food derived from plants.

It clears our stomach.

 

Water –

Our body needs enough water to stay healthy.

Water forms nearly 70% of our body weight.

It is necessary for the proper functioning of the body.

It helps in digestion and removal of wastes from the body.

We lose water through sweating and through urine.

Water helps to regulate the body temperature.

It is an important constituent of blood, skin, digestive juices etc. in our body.

We should drink at least 6 – 8 glasses water every day.

 

Balanced diet – The diet which contains all nutrients in right amount is called balance diet.

Balance diet depends according to the age, gender and occupation of a person.

 

Benefits of Balance Diet

Helps in weight control

Keeps us energized

Supports heart health.

Prevents illnesses

Boosts immune system

Provides all important nutrients

 

Cooking the Food –

Cooking makes the food tasty, soft and easy to digest.

It also kills germs present in raw food.

 

Some tips while Cooking

We should wash the vegetable or fruits before cutting or peeling.

Don’t cooked or deep fry food. It destroys the nutrients.

Don’t wash the vegetables in excess water because its water-soluble nutrients get dissolved in water.

We should not boil or cook vegetable in enough water.

 

Food Preservation:

Preservation – The process by which food is prevented from getting spoilt is called Preservation.

 

Food Preservation:

Food item kept uncovered are exposed to dust and flies.

Flies carry germs on their body and cause diseases like diarrhoea, typhoid etc.

We should avoid eating uncovered and cut food sold in streets.

Foods also get spoiled when they are left for long time as germs grow quickly when there is moisture (water) and warmth.

We can see black, green or grey patches on chapatti or bread kept outside the fridge for many days.

These patches are germs.

 

We can preserve food for long time by using following methods:

Salting: 

It is one of the oldest methods of preserving food.

Fish and pickles preserved in this manner.

Salting preserves food by drawing water out of the food, preventing bacteria growing and spoiling the food.

 

Boiling: 

Boiling controls the growth of germs in food.

That is why we boil milk to prevent it from getting spoilt.

Boiling prevent the food from spoilage for short period of time.

 

Refrigeration: 

Refrigeration is an easy method of preserving food for few days.

It preserves taste, texture, and the nutritional value of foods.

We can keep fruit, vegetables and cooked food in a refrigerator.

 

Dehydration: 

Drying food items under sun rays away water and prevents germs growth.

We can use this method to preserve food items such as raw mango, cauliflower, fish, and potato chips.

 

Sweetening: 

Adding excess sugar to food items also stop germs growth.

We prepare jams, jellies, and murabbas by adding sugar and can preserve them for long time.

 

Drying:

It is a method of removing water from the food to be preserved.

Ex – grapes are dried to form raisins.

 

Canning and bottling:

Canning and bottling of food help to preserve food for a long time.

Examples: sauces and fruit juices

 

Digestion of Food

Digestion – The process in which food nutrients are broken into simpler substances and absorbed by the blood is called digestion.

 

Digestive organs of our body-

Mouth, Food pipe, Stomach, Small intestine, Large intestine, Pancreas, Gall bladder and anus.

 

Process of digestion of food

Explain the Process of digestion of food.

The process of digestion of food starts from mouth and ends at anus.

 

This process occurs in the following steps –

Step-1

Mouth- The food breaks into small peace by teeth and mixed with saliva in the mouth. Saliva digests the starch into sugar in the mouth.

 

Step-2

Food Pipe- The small piece of food than passes through food pipe and goes into stomach.

 

Step-3

Stomach- The small piece of food mixes with gastric juice and breaks the nutrients into simpler form and becomes as thick soup. Proteins digested into stomach.

 

Step-4

Small Intestine- After stomach the thick soup of food comes into small intestine and mixed with juice of liver and pancreas and complete digest the nutrients.

The digested nutrients mix with blood and moves in other parts by the blood vessels.

Liver secretes bile juice that digest the fat.

 

Step-5

Large Intestine- Undigested food comes into largest intestine. Here extra water absorbs by blood vessel in the wall of large intestine. This absorbs water sent to kidneys.

 

Step-6

Anus – Semi solid waste is thrown out from the anus.

 

Digestive system – A system by which food is broken into smaller form and absorbed by the body is called a digestive system. The food that we eat cannot be directly used by our body. It has to be broken down into smaller pieces. Digestion – The process by which food is broken into smaller form and absorbed by the body is called digestion. This process by carried by the digestive system that digestive system consists of the mouth, food pipe, liver, stomach, pancreas, small intestine, large intestine rectum and anus.

 

Here are the major stages of the digestive system: 
Mouth –

The process of digestion begins from the mouth.

The food is softened with help of watery liquid called saliva.

Digestion of carbohydrates begins in the mouth.

The teeth and tongue break the softened food into small parts.

This food is made into a ball called bolus which moves down the food pipe.

 

Chewing –

When you chew your food, it breaks up big pieces into little pieces that are easier to digest and swallow.

 

Swallowing –

Swallowing may seem like a simple process to us. It just sort of happens.

But food doesn’t just fall down our throats into our stomach.

First, our tongue helps to push food into the back of our throat.

 

Food pipe –

It connects mouth to the stomach.

The food in the mouth passes through the food pipe.

The food reaches into the stomach due to the alternate contraction and relaxation of its muscular walls.

 

Stomach –

The stomach is a ‘J’ shaped bag-like organ.

Food hangs out in the stomach for around four hours.

In stomach the food mixes with the digestive juices(enzymes) and acids to breaking down further. Then it goes into small intestine.

The stomach kills a lot of bad bacteria as well, so we don’t get sick. 

 

Small Intestine –

The small intestine is a long, coiled tube.

The food is a completely digested into small intestine.

The digested juices from the liver and the pancreas help in digestion.

All the useful nutrients from the digested food are absorbed by the walls of the small intestine and into the blood.

The blood takes these nutrients to all parts of the body.
 

The Liver and Pancreas –

These are glands which secrete juice to help in digesting food.

Bile is the secretion of the liver and pancreas secretes the pancreatic juice.

Both these glands help in digestion, inside the small intestine.

 

Large Intestine –

Finally, the undigested food enters in the large intestine.

The large intestine absorbs water and minerals from the undigested food and the remaining solid waste called faeces is sent to the rectum.

 

Anus –

The faeces are removed from the body through the anus.

 

Healthy eating habits:

We must wash our hands properly before eating anything.

We must eat small portions of food at regular intervals and not over- eat.

We must eat fresh well-cooked food.

We must chew the food well.

We must eat a balanced diet with fibre rich food.

We must drink a lot of water.