Class 7 Science Chapter 2 MCQ

Human beings do not have cellulose digesting enzymes called “cellulase” but cellulose is still a very important part of human diet. It forms a major part of roughage that is essential for proper digestion.

The liver is a reddish-brown gland situated in the upper part of the abdomen on the right side. It is the largest gland in the body. It secretes bile juice that is stored in a sac called the gall bladder.

Animals that obtain their food by killing other animals, called carnivorous and animals which feed on the remains of dead animals preyed by predators, called scavengers.

The lower part of the small intestine where the intestinal juice completes the digestion of all components of the food. The digested food can now pass into the blood vessels in the wall of the intestine. This process is called “Absorption”.

Stomach is the odd one. It is a digestive organ. All the others are gland.

Digestion of carbohydrate like starch begins in the buccal cavity and the digestion of protein starts in the stomach.

The canines are situated at the ‘corners’ of the dental arches. They have a sharp, pointed biting surface. Their function is to grip and tear food. There are four canine teeth.

Pancreatic juice is a liquid secreted by the pancreas, which contains a variety of enzymes. The pancreatic juice which helps the digestion of starch, called pancreatic amylase. Lipase, helps the digestion of fats and “trypsin” helps the digestion of proteins. The pancreas is located in the visceral region, and is a major part of the digestive system required for proper digestion. Hence, pancreatic juice act on carbohydrates, proteins and fats. Thus, your answer will be option [D].

The “primitive” arrangement of mouthparts is seen in the cockroach (Arthropoda). They are used for biting. There are five different structures which are used for the initial collection and processing of food: Labrum – a cover which may be loosely referred to as the upper lip. Mandibles – hard, powerful cutting jaws. Maxillae – “Pincers” which are less powerful than the mandibles. They are used to steady and manipulate the food. They have a five segmented palp which is sensory and often concerned with taste. Labium – the lower cover, often referred to as the lower lip. It actually represents the fused pair of ancestral second maxillae. They have a three segmented palp which is also sensory. Hypopharynx – a tongue-like structure in the floor of the mouth. The salivary glands discharge saliva through it.

The inner lining of stomach secretes mucus, hydrochloric acid and digestive juices. Out of these HCL kills any bacteria that may enter the stomach with food and makes the medium acidic. Mucus protects the stomach lining from HCL and digestive juices break down proteins in food into simpler substances.

Villi are the finger-like outgrowths of inner surface of human intestine. Their role is to increase the surface area for rapid absorption of digested food. However, in “Amoeba” the finger like projections are called “pseudopodia” that helps it to catch food particles and to move.

All statements are correct about “Amoeba”. Hence, your answer will be option [D].

The food enters into the buccal cavity through mouth. It is chewed by the teeth and mixed with saliva. Saliva contains and enzyme called ptyalin (salivary amylase) which converts complex carbohydrates like starch into sugars. That is why the bread taste become sweet after chewing. This type of digestion is called salivary digestion.

As soon as the food enters the food pipe, the muscles in its wall start alternate contraction and relaxation producing a wave like movement called “Peristalsis”. These movements are essential for pushing the food downwards in the alimentary canal.

The pancreas is a large cream coloured gland located just below the stomach. It is connected to small intestine. Pancreatic enzymes break down food in the small intestine. When food enters the duodenum, it is deluged with pancreatic juice, which is defined as an alkaline secretion of the pancreas containing enzymes that aid in the digestion of proteins, carbohydrates and fats. As: Pancreatic proteases (such as trypsin and chymotrypsin), which help to digest proteins. Pancreatic amylase, which helps to digest sugars (carbohydrates). Pancreatic lipase, which helps to digest fat.

Small intestine is the odd one. It releases intestinal juices and is involved in digestion. All others do not take part in the digestion process.

Molars and premolars perform similar function of chewing and grinding the food. The molars are broader and have different ridge structure than molars. The other types of teeth are: a )Incisors, chisel-shaped for biting and cutting food. b)Canines, large and pointed for piercing and tearing food.

There are four kinds of taste buds which detect sweet, salty and bitter taste. These are located in different parts of the tongue.

The mosquito’s mouth, also called a “proboscis”, isn’t just one tiny spear. It’s a sophisticated system of six thin, needlelike mouthparts that scientists call “stylets”. Each of which pierces the skin, finds blood vessels and makes it easy for mosquitoes to suck blood. (Note: Only female mosquitoes drink blood is so that they can nourish their child-bearing bodies. Blood is full of proteins and amino acids, which makes it the perfect prenatal supplement for growing mosquito eggs, which is why only female mosquitoes drink blood)

The food containing starch (carbohydrate) on reaction with iodine gives blue-black colour, e.g. boiled and mashed potato, a slice of bread. Glucose solution and mustard oil would not give blue-black colour as they are not starch. Mustard oil is fat and glucose is simple unit of carbohydrate.

Here, all the statements are correct. Hence, your answer will be option [D].

Cows, buffaloes and other grass-eating animals (cattle) chewing continuously. Actually, they quickly swallow the grass and store it, in a part of the stomach, called “rumen”. But later the partially digested food (cud) returns to the mouth in small lumps and the animal chews it. This process is called rumination and these animals are called ruminants.

Starch is the odd one. It is a type of carbohydrate. All the others are parts of digestive system of human beings.

Assimilation means utilisation of absorbed food for the purpose of generating energy or obtaining energy through the cells. After you eat, your body breaks down food during digestion, absorbs the nutrients, and distributes them to cells during assimilation. Absorption refers the flow of digested food from the digestive system into the blood system for movement around the body. And assimilation gets the nutrients from your food to your cells where they are used for growth and repair of the all parts of the body. This occurs in the small intestine, in particular the jejunum and ileum.

The saliva breaks down the “Starch” into sugars. The digestive juices (present in the stomach) breaks down the “Protein” into simpler substances. And the bile juice plays an important role in the digestion of “Fats”.