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Question 1

Fill in the blanks:
(a) The main steps of nutrition in humans are __________, __________, __________, _________ and __________.
(b) The largest gland in the human body is __________.
(c) The stomach releases hydrochloric acid and ___________ juices which act on food.
(d) The inner wall of the small intestine has many finger-like outgrowths called _________.
(e) Amoeba digests its food in the ____________ .


a) ingestion, digestion, absorption, assimilation, egestion

These are the basic steps of holozoic nutrition.

1. Ingestion: Ingestion involves the consumption of food by an organism. Animals are variously adapted for ingestion of food of specific types, that intakes through the mouth into the gastrointestinal tract (GI); by eating or drinking processes. In single-celled organisms ingestion takes place by absorbing a substance through the cell membrane or through the surface of the skin.

2. Digestion: Digestion involves the breakdown of large complex organic food molecules (carbohydrates, proteins, lipids, nucleic acid etc.) into the simpler, smaller or soluble molecules so that they can be absorbed into the watery blood plasma. In certain organisms, these smaller substance are absorbed by the small intestine into the blood stream.

3. Absorption: Absorption involves passing of digested food components through the wall of small intestine into the blood of lymph. These absorbed food molecules circulated to different cells of the body where they are being absorbed.  

4. Assimilation: Assimilation involves the movement of digested food molecules into the different cells of the body where they are used. For example: glucose is used in respiration to provide energy to do the processes; and amino acids are used to build new proteins.

5. Egestion: Egestion involves the removal or elimination of undigested food materials from the alimentary canal as faeces.

On reaching the end of the small intestine the digested food products with the minerals and vitamins that are useful to the body, this should have been removed from the watery contents. These materials are then passed on to the large intestine for the forward processes.

(b) liver

Liver is the largest gland which is located in the upper right side of the abdominal cavity. The liver consists of two lobes: the right and the left lobe. The liver is an essential organ weighing body 1.6 kg that has many functions in the body, including making proteins and blood clotting, making of triglycerides and cholesterol, synthesis of glycogen and bile production.

(c) pepsinogen, prorennin etc.

Contraction and the expansion of muscles of the wall of the stomach brings about churning movement which helps in the mixing of food with the gastric juices which is a mixture of HCL, pepsinogen, prorennin, lipase and mucus etc.

(d) villi

Villi are small finger-like numerous microscopic projections found inside the inner walls of the small intestine. Villi absorb nutrients from the food we eat and then shuttle those nutrients into your bloodstream so that they can travel where they’re needed.

(e) food vacuole

A vacuole is a membrane-bound organelle and are kind of vesicle. Vacuoles are closed sacs, made of membranes with inorganic or organic molecules inside such as enzymes. They have irregular shape or size like the cell can change them as needed. They are present in eukaryotic cells and do many things.

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