Science 2 Marks Questions

Glucose is a simple sugar. Carbohydrates, when consumed, have to be digested into glucose. As glucose can be easily absorbed in blood, it provides energy to the body. Hence, when glucose is directly taken, it does not have to be digested and thus acts as an instant source of energy.

Cellulose is a type of carbohydrate that can be digested by ruminants and not by humans. Ruminants have a large sac-like structure between small and large intestine where the food containing cellulose is digested by the action of certain bacteria. On the other hand, humans cannot digest cellulose, as the cellulose digesting enzymes are absent in them.

No.Humans cannot survive only on raw, leafy vegetables, or grass. It is because the grass is rich in cellulose, which is a type of carbohydrate that humans are not able to digest due to the absence of cellulose-digesting enzymes

Gastric juice is secreted by the walls of stomach which contains HCl and Pepsin. HCl helps to kill the germs present in food. After mixing with the food it provides an acidic medium to the food which is essential for the activation of pepsin enzyme. Pepsin digests protein into peptides.

Mucus protects the inner lining of stomach form the action of hydrochloric acid and enzyme pepsin. If mucus is not released, it will lead to erosion of inner lining of stomach leading to acidity and ulcers.

The process by which nutrients from the digested food are absorbed by the body is called absorption whereas the process by which the absorbed nutrients are utilised by the body for providing energy is called assimilation.

Absorbed digested food materials are transported via the blood vessels to different organs of the body where they are used to build complex substances such as the proteins required by the body. This process is called assimilation but the process of removal of waste faecal matter through the anus from time-to-time is called egestion.

The villi increase the surface area for absorption of the digested food. The surface of the villi absorbs the digested food materials and passes them into blood. The absorbed substances are transported via the blood vessels to different organs of the body.

Alimentary canal is a long, muscular coiled tube. It is also known as digestive tract. The alimentary canal with its associated glands constitute the digestive system. These glands are salivary glands, liver and pancreas.

Cellulose is the carbohydrate that can be digested by ruminants. Ruminants have large sac like structure between the small intestine and large intestine which is responsible for digestion of cellulose in them. The cellulose of the food is digested by the action of certain bacteria which are not present in human beings.

Cellulose rich food substances are good source of roughage in human beings. It is because the cellulose digesting bacteria are not present in the body of human beings due to which human beings cannot digest cellulose (present in plant foods).

Glucose is the simplest form of sugar. It can directky be absorbed by intenstine and can easily be transported by blood to various cells of the body. Cells directly act on glucose along with oxygen to given energy.
While carbohydrates are complex forms of sugars and they need to be further broken down into simpler substances like glucose before absorption. Hence it requires extra time as compared to glucose which provides instant energy.

There are different types of enzymes which are used for the digestion of different food materials like carbohydrates, fats, protein etc. The process of digestion involves the association of several catalytic organic compounds such as amylase, pepsin, lipase, trypsin etc. These organic compounds are known as digestive enzymes.

Glucose is the simplest form of carbohydrate that can be easily broken down to give energy. Hence, we get instant energy from glucose. Also, glucose mixes directly into the blood stream making it readily available to the body.

Digestive system of human beings consists of an alimentary canal and associated glands while alimentary canal has mouth, oesophagus, stomach, small intestine, large intestine and Anus.

The inner lining of the stomach secretes mucous, hydrochloric acid and Digestive juices. The mucous protects the lining of the stomach. The hydrochloric acid kills many bacteria that enter along with the food and makes the medium in the stomach acidic. The digestive juices break down the proteins into simpler substances.

Inspite of being blindfolded, one could identify tastes of different drinks with the help of different types of taste buds present in the tongue. Taste buds are sensory taste receptors that help to or perception of taste. There are four kinds of taste buds which detect sweet, salty, sour and bitter taste. These are located in different part of the tongue. Structure of tongue showing position of taste buds.

Sometimes, when we eat hurriedly or talk or laugh while eating, the flap-like valve (called epiglottis) which closes the passage of windpipe remains open. Therefore, the food may enter into the windpipe and it leads to coughing. Coughing helps to clear the passage.

This is done for complete digestion of the food. When the food is swallowed by ruminants, it is only partially digested. It is then again chewed for its completedigestion.

Raw leafy vegetables and grass are rich in cellulose, a type of carbohydrate. Many animals, including humans, cannot digest cellulose, because they do not have enzymes and certain type of bacteria which can digest cellulose. We cannot survive by taking vegetables in raw form. That's why we boil or cook vegetables which breaks down cellulose into simple carbohydrates. We can only survive by taking in vegetables in boiled/ cooked form.

Yes, carnivores animals cannot digest cellulose, hence they have a shorter small intestine. In herbivores, digestion of cellulose takes a longer time.
Hence, herbivores need a longer small intestine to allow complete digestion of cellulose.

The food that remains undigested and unabsorbed enters into the large intestine from small intestine. It is about 1.5 metre in length. Its function is to absorb water and some salts from the undigested food material.

After surgical removal of gall bladder, ‘A’ would face problems in digestion of fatty substances when consumed in bulk. This is because the bile juice stored in the gall bladder helps in digestion of fats. Removal of gall bladder, thus leads to difficulty in digestion of fatty substances.

Food is pushed into the stomach by the peristaltic movement of the walls of oesophagus (food pipe). Sometimes, the food is not accepted by stomach, then the movement of walls of food pipe moves the food in opposite direction and food comes out as vomiting.

Animals like cow cannot chew their food properly due to the presence of cellulose in their diet. At the time they take in food, the food is moistend and is sent for cellulose digestion and softening in rumen.

The swallowed food moves downwards in the alimentary canal because of the atternate relaxation contraction movement of muscles in the wall of foodpipe called peristalsis.

The food items would be fat because bile juice of the gall bladder helps in the digestion of fat. Removal of gall bladder leads to difficulty in digestion of fatty substances.

The first set of teeth grows during infancy and they fall off at the age between six to eight years. These are termed as milk teeth. The second set that replaces them are the permanent teeth. The permanent teeth may last throughout our life or fall off during old age.

The inner walls of the small intestine have thousands of finger-like outgrowths. These are called villi. The villi increase the surface area for absorption of the digested food. Each villus has a network of thin and small blood vessels close to its surface. The surface of the villi absorbs the digested food materials. The absorbed food is then transported to various organs via blood vessels.

Bile is produced in liver and is stored in a sac like structure called the gall bladder. The bile plays an important role in the digestion of fats, it acts on fat and convert them into simpler form.

The mode of feeding of:Ant: scraping and the mode of feeding of.
Mosquitoes: sucking.

The intense pressure is formed in the stomach when the food is not accepted by the stomach. The content in the stomach is then pushed back. This returned content is expelled out from the mouth in the form of vomiting.

The three digestive glands are:

1. Liver.
2. Pancreas.
3. Salivary glands.

The main organs of digestive system are liver, Gall bladder Stomach, Pancreas, Small intestine, Large intestine, Rectum, Anus. The digestive tract and the associated glands together constitute the digestive system.

The finger-like projections called villi are present in the inner walls of the small intestine. The villi increase the surface area. The large surface area of small intestine helps in the rapid absorption of the digested food.

Similarity: Both amoeba and human beings use digestive juices for digestion of food.
Difference: Humans need to chew food whereas in amoeba, there is no chewing of food.

Ruminants quickly swallow the grass and store it in a separate part of the stomach called rumen. Here the food gets partially digested and is called cud. Later the cud returns to the mouth in small lumps and the animal chews it. This process is called rumination. The cellulose present in grass is digested here by the action of certain bacteria which are not present in humans.

Cellulose, a type of carbohydrate present in grass and it can be digested by ruminants but not by humans. Ruminants have a large sac-like structure between the small intestine and large intestine called caecum. The cellulose of the food is digested here by the action of certain bacteria which are not present in humans.