Class 10 Science Chapter 6 MCQ

Heterotrophs are those organisms which cannot make their own food from inorganic substances like CO2 and water as they do not have chlorophyll to trap solar energy, e.g., all animals, most bacteria and fungi. They depend on other organisms for their food. Autotrophs synthesize their own food through photosynthesis by utilising solar energy. e.g., green plants.

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.

Food comes first in Mouth and then moves through Oesophagus and stomach → small intestine → large intestine.

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

The solution turned blue-black in colour just because of starch.

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.

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].

Valves allow the flow of blood in one direction only.

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.

Oxygen liberated during photosynthesis comes from water. The following events occur during 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, which is used as food for plants

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 mucus is secreted in the gastric juice by the glands present in the stomach wall. It helps to protect the wall of stomach from its own secretions of hydrochloric acid. If mucus is not secreted, HCI will cause the erosion of inner lining of stomach leading to ulcer formation. Pepsin acts on proteins in the stomach. Salivary amylase is present in saliva, it acts on starch in the mouth. Bile helps in emulsification of fat in small intestine.

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

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.

Arteries are the vessels which carry blood away from the heart to various organs of the body. Since the blood emerges from the heart under high pressure, the arteries have thick, elastic walls. Veins collect the blood from different organs and bring it back to the heart. They do not thick walls because the blood is no longer under pressure, instead they have valves that ensure that the blood flows in only one direction.

Non-living things which are not alive cannot move by themselves. For example, a stone is a non-living thing which cannot move by itself from one place to another or show any other type of movement. We will have to move it by applying force from outside.

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.

Nitrogen is an essential element used in the synthesis of proteins and other compounds. This is taken up in the form of inorganic nitrates or nitrites.

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.

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.

Generally, the normal blood pressure values are: Systolic pressure: 120 mm Hg Diastolic pressure: 80 mm Hg This is usually written as 120 by 80.

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.