Food and Nutrition In Living Organisms, All details and important MCQs

This section deals with food and nutrition. here we have discussed topics like ” food and its constituents”, “nutrition in plants” and nutrition in animals”. You will also get to solve various important MCQs on the topic at the end of this section.

What is food?

Food comprises of all such things that plants or animals eat to survive.

Food Provides energy and nutrition and it is enjoyable to humans. Food substance consist of proteins, carbohydrates, fats, and other nutrients used in the body of an organism to sustain growth and carry out vital processes.

Substances lik protein, fat, carbohydrates, vitamins, water and minerals are called constituents of food. The functions of these food components are listed below:

Food ComponentFunction
CarbohydrateThey are broken down into glucose which then provides energy.
FatProvides energy, protection and insulation to the body.
ProteinsAct as building blocks, assist in metablosim, act as enzymes and hormones
VitaminsHelp in boosting immune system, making bones stronger, healing wounds and also act as co-enzymes.
WaterHelp in absorption of nutrients and removal of waste products. Acts as a thermoregulator in the body.

What is nutrition?

Nutrition is the process of providing or obtaining the food necessary for health and growth. Nutritional process comprises of various stages, that are ingestion, digestion, absorption, transport, assimilation, and finally egestion/excretion.

Nutrition In Animals

Animals derive their nutrition from plants either by eating them directly (herbivores), or indirectly by eating animals which have consumed plants (carnivores). The animals which eat both plants and animals are known as omnivores.

The nutrition in animals consists of following steps:

  1. Ingestion: It refers to the intake of food.
  2. Digestion: It means breaking down food into simpler water soluble components. It involves both physical and chemical changes. For example, chewing of food is simply a physical change, while action of salivary amylase on starch to convert into Maltose and Dextrin is a chemical change.
  3. Absorption: In this step, the digested food is abosrbed into blood to carry it to different parts of the body.
  4. Assimilation: It refers to the actual use of the absorbed food for a variety of purposes like fulfilling energy requirements of each cell, and healing of wounds etc.
  5. Egestion/Excretion: This is the final step and involves the removal of waste products from the body.

Human Digestive System

The human digestive system consists of the alimentary canal and the associated glands.

The alimentary canal begins with an anterior opening – the mouth.

The oral cavity has a number of teeth and a muscular tongue. Each tooth is embedded in a socket of jaw bone. Human teeth are deciduous in nature. The milk teeth are 20 in number and the permanent teeth are 32 in number.

The dental formulla in a child is 2102/2102 and dental formulla of an adult is 2123/2123.

The digestive system is essentially a long, twisting tube that runs from the mouth to the anus, plus a few other organs (like the liver and pancreas) that produce or store digestive chemicals.

Food is partly broken down by the process of chewing and by the chemical action of salivary enzymes (these enzymes are produced by the salivary glands and break down starches into smaller molecules).

Once the food is broken down in the stomach and mixed with digestive juices, it is called chime.

The stomach, located in the upper left portion of the abdominal cavity, has four major parts – a cardiac portion into which the oesophagus opens, a fundic region, body (main central region) and a pyloric portion which opens into the first part of small intestine. The stomach stores the food for 4-5 hours.

The mucosa of stomach has gastric glands. Gastric glands have three major types of cells namely –

(i) mucus neck cells which secrete mucus;

(ii) peptic or chief cells which secrete the proenzyme pepsinogen; and

(iii) parietal or oxyntic cells which secrete HCl and intrinsic factor (factor essential for absorption of vitamin B12).

The opening of the stomach into the duodenum is guarded by the pyloric sphincter.

The innermost layer lining the lumen of the alimentary canal is the mucosa.

Pancreas – secretes digestive enzymes, produces the hormone insulin that regulates blood sugar levels.

In the small intestine, bile( produced in the liver and stored in the gall bladder), pancreatic enzymes, and other digestive enzymes produced by the inner wall of the small intestine help in breakdown of food.

Large Intestine: It removes water from the chyme and gets the waste ready for excretion. Many bacteria like microbes in the large intestine hel in the digestion process.

From the small intestine, food that has not been digested along with some water, travels to large intestine through a valve that prevents food from returning to the small intestine.


Autotrophic Organisms – They can prepare their food by themselves such as plants.

Heterotrophic Organisms – They depend upon other organisms for their food such as animals.

Plants are the only organisms that can prepare food for themselves by using water, carbon dioxide and minerals.

Water and minerals present in the soil are absorbed by the roots and transported to the leaves.

Water and minerals are transported to the leaves by the vessels which run like pipes throughout the root, the stem, the branches and the leaves.

These organisms are called fungi. They have a different mode of nutrition. They absorb the nutrients from the bread. This mode of nutrition in which organisms take in nutrients from dead and decaying matter is called saprotrophic nutrition.

Some organisms live together and share both shelter and nutrients. This relationship is called symbiosis.

The process by which plants prepare their food by using these raw materials is called Photosynthesis.

In organisms called lichens, a chlorophyll-containing partner, which is an alga, and a fungus live together.

Transportation of water and Minerals in plants – The roots of the plants absorbs the water and minerals of the soil and then transports them to the leaves via stems and branches.

TRANSLOCATION: The bulk movement of substances through the conducting or vascular tissues of plants is called translocation.

In a flowering plant the substances that would need to be transported are water, mineral nutrients, organic nutrients and plant growth regulators.

There are tiny holes or pores present on the surface of the leaves called Stomata that take in the carbon dioxide present in the atmosphere.

DIFFUSION: Movement by diffusion is passive, and may be from one part of the cell to the other, or from cell to cell, or over short distances, say, from the inter cellular spaces of the leaf to the outside.

ACTIVE TRANSPORT: Active transport is that mode of transportation that uses energy to move and pump molecules against a concentration gradient.

Active transport is carried out by specific membrane-proteins.

TRANSPIRATION: Terrestrial plants take up huge amount water daily but most of it is lost to the air through evaporation from the leaves, i.e., transpiration.

Water is essential for all physiological activities of the plant and plays a very important role in all living organisms. It provides the medium in which most substances are dissolved.

MCQs On Food And Nutrition

This section contains many important MCQs on food and nutrition in animals and plants. Solve these MCQs on food and nutrition to check and enhance your level of preparation for competitive exams.

The autotrophic mode of nutrition requires:

  1. Carbon dioxide and water
  2. Sunlight
  3. Chlorophyll
  4. All of the above

All of the above

What is the dental formula of an adult human?

  1. 2123
  2. 2213
  3. 2132
  4. 2231


The acid contained in the stomach juice is:

  1. Citric acid
  2. Nitric acid
  3. Hydrochloric acid
  4. Sulphuric acid

Hydrochloric acid

The enzyme contained in salivary juice is known as:

  1. Ptyalin
  2. Lipase
  3. Protease
  4. Trypsin

Ptyalin. It is also known as salivary amylase

Which of the following acts as a food factory for a plant?

  1. Stem
  2. Leaves
  3. Flower
  4. Seeds

Leaves. As they are the photosynthetic organs

Bile juice is produced by:

  1. Salivary glands
  2. Gall Bladder
  3. Liver
  4. Stomach


Which of the following is the correct arrangement of the food constituents as far as their gross calorific values are concerned.

  1. Proteins>Fats>Carbohydrates
  2. Carbohydrates>Fats>Proteins
  3. Fats>Carbohydrates>Proteins
  4. Fats>proteins>carbohydrates

Fats>proteins>carbohydrates. The heat released by combustion of one gram of food is usually known as its gross calorific value. The gross calorific value in Kcal/g of carbohydrate, protein and fats is 4.1, 5.65 and 9.45 respectively.

Fungi are:

  1. Autotrophic in nature
  2. Hetereotrophic in nature
  3. Saprotrophic in nature
  4. none

Saprotrophic. saprotroph, also called saprophyte or saprobe, is an organism that feeds on nonliving dead decaying organic matter known as detritus at a microscopic level.

Which of the following is a necessary evil?

  1. Absorption
  2. Photosynthesis
  3. Transpiration
  4. All of the above

Transpiration. Transpiration and friction are considered as necessary evils, as they are important but have intrinsic disadvantages.

After photosynthesis, carbohydrates are converted ultimately into:

  1. Glucose
  2. Maltose
  3. Sucrose
  4. Starch


Animals store food in the form of:

  1. Carbohydrate
  2. Protein
  3. Glycogen
  4. Starch


These were some important MCQs on food and nutrition in living organisms. We are sure that you will find these MCQs on food and nutrition in living organisms very useful and hope that you will share them with your friends.

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