Class 10 Science Chapter 6 MCQ

The various organs in sequence of mouth, oesophagus, stomach, small intestine and large intestine and anus. The nutrition in human beings take place through the digestive system, that consists of alimentary canal and associated glands.

Chloroplast are the organelles in the cells of green plants which contain chlorophyll and where photosynthesis take place. Thus, photosynthesis occurs in the organelles called the chloroplast present in the photosynthetic cell or mesophyll cell of green plants. In the other words, the site of photosynthesis in cell of the leaf are chloroplast. Chloroplast can be seen easily by using a light microscope.

It is incorrect as; autotrophs can convert carbon dioxide and water into carbohydrates only in the presence of sunlight. The autotrophs contain the green pigment called chlorophyll which is capable of trapping sun energy. This trapped energy is utilised by them to make food by combining inorganic materials like CO2 and H2O by the process of photosynthesis. The food that is not used immediately, is stored in the form of starch. These autotrophs constitute the first trophic level in food chains.

Pyruvic acid is converted into lactic acid in the cytoplasm of muscles cells during deficiency of oxygen in human beings.

Energy is required by an organism even during sleep because when we are asleep a number of biological processes keep on occurring in the body which require energy. Our heart beats non-stop even when we are asleep to pump blood throughout the body. And this beating of heart requires energy. Thus, the working of heart requires are continuous supply of energy.

The digestion of food completed in Small intestine. In large intestine only absorption of water take place. In mouth cavity the digestion starts only. In stomach, the digestion of proteins start in acidic medium with the help of pepsin.

Digestion process starts from the mouth where salivary glands are present. Salivary glands produce amyloses. So, amylase is the first enzyme to mix with food. The saliva secreted by the salivary glands in mouth contains this enzyme that breaks down starch. Pepsin is a protein digesting enzyme secreted by the gastric glands present in the stomach wall. The pancreas secretes pancreatic juice in the small intestine. It contains enzymes like trypsin for digesting proteins. Cellulase is an enzyme complex which breaks down cellulose. Most animals, including humans (except ruminants) do not produce cellulase and are therefore unable to use most energy contained in plant material.

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

The summary equation of photosynthesis is: 6CO2 + 12H20+ Chlorophyll +Sunlight → C6H12O6 +6CO2 + 6H2O by using. Photosynthesis is a process by which green plants make their own food, e.g., glucose, CO2 and H2O in the presence of sunlight energy and chlorophyll in the presence of. Oxygen gas is released during the process of photosynthesis.

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

Oxygen-rich blood from the lungs comes to the thin-walled upper chamber of the heart on the left, the left atrium. The left atrium relaxes when it is collecting this blood. It then contracts, while the next chamber, the left ventricle, relaxes, so that the blood is transferred to it. When the muscular left ventricle contracts in its turn, the blood is pumped out to the body. De-oxygenated blood comes from the body to the upper chamber on the right, the right atrium, as it relaxes. As the right atrium contracts, the corresponding lower chamber, the right ventricle, dilates. This transfers blood to the right ventricle, which in turn pumps it to the lungs for oxygenation. Since ventricles have to pump blood into various organs, they have thicker muscular walls than the atria do. Valves ensure that blood does not flow backwards when the atria or ventricles contract.

A cell is the basic structural and functional unit of a living being. Each cell is made up of molecules. The molecules exhibit movement during cellular reactions that lead to life activities but their movements of molecules do not take place in the cells. The growth of a living organism starts with the division of its cells. All living things have an organised structure, which if breaks down leads to various diseases, disorders and even death. Therefore, the living things have to repair and maintain their structures through various processes. These life processes require energy which is obtained from food.

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

Small intestine receives bile from the liver which is normally stored in the gall bladder. It performs two functions i.e. makes the food alkaline and break the fats present in food into small globules by the process of emulsification.

The human saliva contains an enzyme called salivary amylase, which breaks down the starch present in food into sugar. The digestion of starch (carbohydrates) begins in the mouth. In case, saliva is lacking, it will affect the break-down of starch. The protein digestion begins in the stomach by the enzyme pepsin and completes in small intestine by enzyme trypsin, chymotrypsin, carboxypeptidases, aminopeptidases and dipeptidases. The fats are broken down into small particles by bile in small intestine and then broken-down fatty acids and glycerol by lipases present in pancreatic juice. Absorption of vitamins takes place in the small intestine.

Pisces have only two chambers to their hearts, and the blood is pumped to the gills, is oxygenated there, and passes directly to the rest of the body. Thus, blood goes only once through the heart in the fish during one cycle of passage through the body.

The following events occur in photosynthesis (i) Absorption of light energy by chlorophyll. (ii) Conversion of light energy to chemical energy and splitting of water molecules into hydrogen and oxygen. (iii) Reduction of carbon dioxide to carbohydrates.

In Pisces (fishes), the heart is 2 chambered oral pumps deoxygenated blood to the gills, where oxygenation takes place by diffusion. The oxygenated blood from the gills is supplied to the body parts where oxygen is utilised and CO2 enters it making the blood deoxygenated. This deoxygenated blood returns to the heart. Thus, it has single circulation, i.e., blood passes through the heart only once during one complete cycle.

Single circulation is found in fishes. Hippocampus, Exoceotus, Anabas exhibit single circulation of blood because these animals belong to Pisces.

Left ventricle pumps oxygenated blood to different body parts while right ventricle pumps deoxygenated blood to lungs. Whereas right atrium receives deoxygenated blood from different parts of the body while left ventricle pumps oxygenated blood to different parts of the body. Hence, Deoxygenated blood flows through the right side of the heart. Oxygenated blood flows through the left side of the heart.

The opening and closing of the pore is a function of the guard cells. The guard cells swell when water flows into them, causing the stomatal pore to open. Similarly the pore closes if the guard cells shrink.

When we breathe in, we lift our ribs and flatten our diaphragm, the chest cavity becomes larger. Alveoli is balloon like structure which provides a surface where the exchange of gases occurs the walls of alveoli consist of network of blood-vessels. The air is sucked into the lungs to fill the expanded alveoli. The blood brings carbon dioxide from the rest of the body for release into the alveoli. And the oxygen in the alveolar air is taken up by blood in the alveolar blood vessels to be transported to all the cells in the body. In human beings, the respiratory pigment is haemoglobin which has a very high affinity for oxygen. This pigment is present in the red blood corpuscles. The human lungs have millions of air sacs called alveoli whose surface area is many that of the body. These are involved in exchange of gases.

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

Carbon dioxide gas turns limewater milky. When air is blown from mouth into test, the lime water turns milky because the air we breathe out has more CO2.

The small intestine in human beings is the site of complete digestion of food. It is also the main region for absorption of digested food. However, digestion begins in the mouth cavity, food is further digested in the stomach to form a semi-solid paste. The undigested food from small intestine passes into large intestine that absorb most of the water.