Class 10 Science Chapter 5 MCQ

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.

The first step is the break-down of glucose, a six-carbon molecule, into a three-carbon molecule called pyruvate. This process takes place in the cytoplasm.

Fermentation is a form of anaerobic respiration. Pyruvate can be converted into ethanol and CO, in yeast during fermentation. Since this process takes place in the absence of air (oxygen), it is called anaerobic respiration. It takes place in cytoplasm. Break down of pyruvate using oxygen, i.e., aerobic respiration takes place in the mitochondria.

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

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.

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

Large number of tiny pores called stomata are present on the surface of the leaves of plants. The gaseous exchange as well as transpiration takes place through these pores. 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 pores to open. Similarly, the pore closes if the guard cells shrink or losses water in them.

Green plants are autotrophic and synthesize their own food by the process of photosynthesis. The process of photosynthesis can be represented as: 6CO2 + 6 H2O + Sunlight + Chlorophyll → C6H12O6 + 6O2 (releases)

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

In autotrophs, the cellular energy reserve is starch. However, carbohydrates serve as a major fuel in the cells to provide energy for life processes. The sugar (glucose) produced that is not used immediately gets stored in the form of starch in plants. In animals, food is stored in the form of glycogen. These food reserves provide energy as and when required by the organisms.

The blood leaving the tissues becomes richer in CO2. The main artery (aorta) carries oxygenated blood to all the organs of the body from the heart. When the oxygenated blood passes through the capillaries of the body organs/tissues, it gives oxygen to the body cells. At the same time, carbon dioxide produced during respiration enters into blood. Thus, deoxygenated blood (carrying CO2) leaves the tissues and enters the vena cava, from where they are again passed to the lungs for oxygenation.

Amoeba has no fixed place for removing the undigested part of food. When a considerable amount of undigested food collects inside Amoeba, then its cell membrane suddenly ruptures at any place and the undigested food is thrown out the body of Amoeba.

Nephrons are the filtration units of kidneys. It is the structural and functional unit of a kidney and has three functions – filtration, reabsorption and secretion. Urine from the kidney passes through a tube called ureter, that carry urine into the urinary bladder. The urethra is a canal that carries urine from bladder and expels it out of body. Neurons nerve cells and are functional units of nervous system.

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.

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.

Since the blood emerges from the heart under high pressure, the arteries have thick, elastic walls.

During the photosynthesis, the following steps take place: (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.

It is in the alveoli in the lungs where gaseous exchange takes place. The walls of the alveoli are very thin and surrounded by network of very thin blood capillaries. The presence of millions of alveoli in the lungs provides a large area for the exchange of gases.

The whole process of an aerobic respiration take place in the cytoplasm of cells.

When there is a lack of oxygen in our muscle cells, another pathway for the break-down of pyruvate is taken. Here the pyruvate is converted into lactic acid which is also a three-carbon molecule. This build-up of lactic acid in our muscles during sudden activity causes cramps.

Mitochondria are the sites of aerobic respiration in the cells. The breakdown of pyruvate to give carbon dioxide, water and energy takes place in mitochondria.

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.

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.

The blue black colour of rice water confirms the presence of starch. No colour change will be seen in case of proteins fats in iodine solution colour, when iodine is added with them. Note: A starch solution on addition of iodine turns blue black in colour.