[5 Mark Question Answer]

Question 15 Marks

Answer in detail.
You had eaten bread in the morning. Starting from the mouth, explain how it is digested?

Answer

Bread contains starch. The digestion of starch starts in the mouth. When we chew the bread, saliva gets mixed with it. It softens the food. Saliva is secreted by salivary glands. Saliva contains the enzyme salivary amylase (ptyalin) which acts on starch to convert it into maltose
starch$\xrightarrow[\text { amylase }]{\text { salivary }}$maltose.
After chewing, the food is swallowed into the pharynx. No further digestion takes place in the pharynx. From here the food moves in to the oesophagus, by peristaltic movements it is pushed in to the alimentary canal. In the small intestine (duodenum) rest of the starch is broken down into smaller units by pancreatic amylase. Further Maltose is changed into glucose by maltose in the small intestine (ileum).

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Question 25 Marks

Answer in detail.
What happens to the nutrients absorbed in the bloodstream from the small intestine?

Answer

The villi of the small intestine increase the inner surface area for the absorption of digested food. Villi contain blood capillaries, The digested food passes through these blood capillaries and enters the bloodstream. This process is called absorption. All the absorbed nutrients are not required immediately by the body. So they are changed into various forms that can be stored until they are needed. This process is called assimilation.
1. Glucose is converted into glycogen and is stored in the liver. When it is required by the liver glycogen is converted into glucose. Excess of glucose is also converted in to fat and stored in the adipose tissue. Fatty acids either provide energy or are used for the synthesis of fats which is stored under the skin.
2. Amino acids are used for the synthesis of protein. Excess amount of amino acids are converted into urea which is removed by the kidneys.
glucose$\xrightarrow{\text { liver }}$glycogen
Amino acids →Proteins
Amino acids → urea

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Question 35 Marks

Answer in detail.
What changes occur in food in the mouth?

Answer

The mouth is the first part of the digestive system. It receives food and starts mechanical digestion. The ingested food is first broken down in the mouth when it is chewed. Simultaneously it gets mixed with the saliva. This process is called mastication or mechanical digestion. It prepares the food for chemical digestion, that is, the digestion by action of enzyme. The teeth help in chewing down the food. There are 4 kinds of teeth. These are incisors, canines, premolars and molars, incisors are the cutting teeth. These help in biting and cutting the food. Canines are the tearing teeth that helps to tear and hold the food. Premolars and molars are the crushing and grinding teeth which help in grinding the food. When we chew the food it is mixed with saliva, secreted by salivary glands softens the food. Saliva contains an enzyme called salivary amylase also called ptyalin, acts on starch to convert it into maltose.
starch$\xrightarrow[\text { amylase }]{\text { salivary }}$maltose.

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Question 45 Marks

Answer in detail.
Name the four types of teeth and their functions

Answer

The four types of teeth are:
Incisors: These are situated at the front and are flat and straight with sharp edges. Which are used for biting and cutting the food.
Canines: These are situated one on either side of the incisors in each jaw. There are two canines in each jaw. These are sharp and pointed and are used for holding and tearing the food.
Premolars: There are 4 premolars in each jaw, situated next to the canines. Each premolar has one or two roots and two cusps. These are used for crushing and grinding the food.
Molars: These are 6 molars in each jaw. The molars have more than one root. These are used for crushing and grinding the food. The last molar of each side in each jaw is also called wisdom tooth because it appears last generally at the age of 17-20 years. The ingested food is first broken down in the mouth when we chew it with our teeth. This process is called mastication or mechanical digestion. It prepares the food for chemical digestion that is, digestion by the action of enzymes.

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Question 55 Marks

Answer in detail.
What is meant by digestion? How does it differ from nutrition?

Answer

The process of changing complex food into simple, absorbable form by the action of certain enzymes is called digestion. Many organs are associated with digestion. Digestion is of two types
1) Mechanical digestion
In mechanical digestion, food is broken down in the mouth when we chew it with our teeth.
2) Chemical digestion.
In chemical digestion, the food is digested by the actions of certain enzymes.
Digestion is necessary because the food which is obtained is in complex form and our body is not able to absorb nutrients from it. So it is converted into a simple absorbable form. Nutrition is the process of obtaining and using food by the organisms. It is different in different organisms. Ingestion, digestion, absorption, Assimilation, and egestion are the various steps involved in nutrition.

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BIOLOGY [5 Mark Question Answer]

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