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.

Starch breaking down into sugars and later on in Stomach it further break down in glucose.

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

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.

Cells generally does not share the transaction of the particles or molecules.

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.

Organisms which can make their own food from carbon dioxide and water are called autotrophs. Carbon dioxide and water are inorganic substance. So, we can say that, those organisms which can make their own food from the inorganic substances present in the environment are called autotrophs. All the green plants are autotrophs.

Carbon dioxide is used in photosynthesis for the products on of food. The oxidation of carbon compounds occurs in respiration.

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

Alveoli of lungs. The walls of the alveoli contain an extensive network of blood-vessels. When we breathe in, we lift our ribs and flatten our diaphragm, and the chest cavity becomes larger as a result. Because of this, air is sucked into the lungs and fills 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.

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.

The oesophagus carries food to the stomach. When the slightly digested food enters the food pipe, the walls of food pipe start contraction and expansion movements. The contraction and expansion movement of the walls of food pipe is called peristaltic movement. This peristaltic movement of food pipe pushes the slightly digested food into the stomach.

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.

Hippocampus, Exocoetus, Anabas. Because the rate of energy required for the body activities is very low.

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.

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.

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.

Fermentation is a form of anaerobic respiration in which Pyruvate can be converted into ethanol and carbon dioxide by yeast.

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.

Aerobic respiration uses oxygen for respiration. It takes place in the mitochondria. After glycolysis, pyruvate (from cytoplasm) enters the mitochondria and is oxidised in a series of reactions, to form considerable amount of energy (ATP), CO2 and H2O.

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.