Please refer to Chapter 6 Life Processes Class 10 Science Important Questions with solutions provided below. These questions and answers have been provided for Class 10 Science based on the latest syllabus and examination guidelines issued by CBSE, NCERT, and KVS. Students should learn these problem solutions as it will help them to gain more marks in examinations. We have provided Important Questions for Class 10 Science for all chapters in your book. These Board exam questions have been designed by expert teachers of Standard 10.
Class 10 Science Important Questions Life Processes Chapter 6
Very short Answer:
Question: Name the intermediate and the end products of glucose breakdown in aerobic respiration.
Answer: The intermediate product of glucose breakdown in aerobic respiration is pyruvate whereas the end products are carbon dioxide and water.
Question: Name the green dot like structures in some cells observed by a student when a leaf peel was viewed under a microscope. What is this green colour due to?
Answer: The green colour of the leaves of the plant is due to the presence of tiny green coloured organelles called chloroplasts which contain green pigment chlorophyll.
Question: State the basic difierence between the processof respiration and photosynthesis.
Answer: Respiration involves breakdown of food (like glucose) by using oxygen and releasing carbon dioxide, water and energy whereas photosynthesis is synthesis of food (like glucose) by using carbon dioxide, water and sunlight and releasing oxygen. Therefore, respiration is just reverse of photosynthesis.
Question: How do autotrophs obtain CO2 and N2 to make their food?
Answer: Green plants take carbon dioxide (forcarbohydrates) required for photosynthesis directly from atmospheric air and nitrogen (for proteins) in the form of soluble nitrogen compounds present in the soil.
Short Answer:
Question: Name the tissue which transports soluble products of photosynthesis in a plant.
Answer: The phloem is a vascular tissue that transports soluble products of photosynthesis (food or sugar) to all the parts of plants.
Question: Write any three difierences between aerobic and anaerobic respiration.
Answer: Differences between aerobic and anaerobic respiration are as follows:
Long Answer:
Question: (a) List the three events that occur during the process of photosynthesis. Explain the role of stomata in this process. (b) Describe an experiment to show that “sunlight is essential for photosynthesis.”
Answer: (a) The three events that occur during the process of photosynthesis are :
(i) Absorption of light energy by chlorophyll : It takes place in grana region of chloroplast. During light reaction, radiant energy of sun is trapped by photosynthetic pigments like chlorophyll and accessory pigments. When exposed to light, chlorophyll molecule is excited and emits electrons.
(ii) Conversion of light energy to chemical energy and splitting of water molecule into hydrogen and oxygen : Emitted electrons from chlorophyll are channeled through electron transport chain in chloroplast. The energy absorbed by chlorophyll is responsible for carrying out three functions:
(i) formation of ATP, (ii) photolysis of water and (iii) synthesis of NADPH (Reduced nicotinamide adenine dinucleotide phosphate).
(iii) Reduction of carbon dioxide to carbohydrate: Carbon dioxide is reduced to glucose (carbohydrate) by the hydrogen in NADPH and by utilising the chemical energy stored in ATP. Stomata play an important role in photosynthesis, as gaseous exchange in plants take place through the stomata. Stomata are tiny pores present on the surface of the leaves (also on other green parts like stem). Carbon dioxide required for photosynthesis enters the leaves of the plant through stomata. A large amount of water is also lost through stomatal pores and oxygen released as by product of photosynthesis goes out through stomatal pores of leaves.
(b) Experiment to show that sunlight is necessary for photosynthesis.
(i) Take a potted plant having green leaves and place it in a completely dark place for about three days to destarch its leaves.
(ii) Take a thin strip of aluminium foil (or black paper) and wrap it in the centre of one leaf on both the sides (while the leaf is still attached to the plant). The aluminium foil should be fixed tightly to the leaf by using paper clips so that sunlight may not enter it from the sides. The aluminium foil should cover only a small part of the leaf so that
the remaining part of the leaf remains uncovered and exposed to sunlight.
(iii) Keep this potted plant (with partially covered leaf) in bright sunshine for three to four days.
(iv) Pluck the partially covered leaf from the plant and remove its aluminium foil. Immerse this leaf in boiling water for a few minutes.this will break down the cell membranes of leaf cells and make the leaf more permeable to iodine solution. This leaf is now to be tested for the presence of starch. But before testing for starch, chlorophyll has to be removed from the leaf.
(v) Now put the leaf in a beaker containing some alcohol. Place the beaker containing alcohol and leaf in a water bath.
(vi) Heat the water in the bigger beaker. Then the alcohol in the smaller beaker will also get heated and start boiling soon. is boiling alcohol will extract (or remove) chlorophyll from the green leaf.
(vii) Boil the green leaf in alcohol till all its green pigment ‘chlorophyll’ is removed. The leaf will now become almost colourless or pale (and the alcohol will turn green).
(viii) Remove the colourless leaf from alcohol andwash it thoroughly with hot water to soften it and remove any chlorophyll which may be sticking to it.
(ix) Place the colourless leaf in petri-dish. Drop iodine solution over the decolourised leaf with the help of a dropper. Observe the change in colour of leaf.
(x) The middle part of leaf which was covered with aluminium foil does not turn blue-black on adding iodine solution showing that no starch is present in this middle part of the leaf. is is because sunlight could not reach the covered ‘middle part’ of the leaf due to which the covered ‘middle part’ of leaf could not do photosynthesis to make starch.
(xi) The uncovered part of leaf which was exposed to sunlight turns blue-black on adding iodine solution showing that starch is present in this part of leaf.
(xii) Since the part of leaf which was covered and hidden from sunlight does not contain starch but the part of leaf which was exposed to sunlight contains starch, therefore, we conclude that sunlight is necessary for photosynthesis (to make food like starch).
Question: (a) Draw a diagram of human alimentary canal and label on it: oesophagus, gall bladder, liver and pancreas.
(b) Explain the statement, ‘bile does not contain any enzyme but it is essential for digestion.’
Answer: (a) The diagram labelled of human alimentary canal is as follows:
(b) Bile is a dark green to yellowish brown fluid secreted by liver and stored as well as concentrated in the gall bladder. Bile does not contain any digestive enzymes like other secretions from gastrointestinal tract instead has salts which emulsify fats (that are in the form of complicated triglycerol) and breaks it down into small fat droplets that can easily be acted upon by fat digesting enzymes. This is actually a detergent like action of bile. Therefore, bile is essential for digestion though it does not contain any digestive enzyme.
Question: Explain the process of digestion of food in mouth, stomach and small intestine in human body.
Answer: The process of digestion of food in mouth, stomach and small intestine in human body is as follows :
(i) Mouth : Food is chewed with the help of premolars and molars which increases the rate of action of salivary amylase. Food is mixed with saliva of salivary glands. Salivary amylase hydrolyses about 30-40% of starch into maltose and isomaltose at pH 6.8.
(ii) Stomach : Food is mixed with gastric juice which contains mucus, hydrochloric acid, pepsin, rennin and a weak lipase enzyme. Mucus lubricates the food and protects the inner lining of the stomach from the action of acid. Hydrochloric acid stops the action of saliva in stomach, kills the bacteria present in the food and provides acidic medium (pH 1-2) of gastric juice so that pepsin gets active for protein digestion. Pepsin hydrolyses proteins into proteoses and peptones, while gastric lipase enzymes hydrolyses small amounts of fats into fatty acids and glycerol. Curdling of milk is done by the enzyme rennin, which increases the period of action of pepsin on milk proteins
In addition to chemical digestion, food also undergoes mechanical churning inside the stomach.
(iii) Small intestine : Food is mixed with three digestive juices : bile juice of liver; pancreatic juice of pancreas and intestinal juice of intestinal glands. Bile juice neutralises the acidity of the food coming from the stomach and provides alkaline medium and emulsifies (breaks down with the help of bile salts) larger fat globules into smaller fat droplets but is a non-enzymatic digestive juice so has no chemical action on food.
Pancreatic juice contains a number of enzymes like trypsin, pancreatic amylase and pancreatic lipase, which digest the peptones, starch and fats into peptides, maltose, isomaltose and fatty acids respectively
Intestinal juice also contains number of enzymes like aminopeptidase, intestinal amylase, maltase, isomaltase and lipase enzymes which hydrolyse peptides to amino acids, starch to maltose, maltose to two glucose, isomaltose to two glucose and fats to fatty acids and glycerol. So, small intestine is the site of the complete digestion of carbohydrates, proteins and fats.
Question: (a) Draw a diagram depicting human alimentary canal and label on it: gall bladder, liver and pancreas.
(b) State the role of liver and pancreas.
(c) Name the organ which performs the following function in human.
(i) Absorption of digested food (ii) Absorption of water
Answer: (a) The diagram labelled of human alimentary canal is as follows:
(b) Liver is the largest gland of the body that secretes bile juice. Bile juice neutralises acidity of food coming from stomach and provides alkaline medium and helps in digestion of fats in small intestine by bringing about fat emulsification (conversion of large fat droplets into smaller ones) making it easier for enzymes to act and digest them. Pancreas is a soft, lobulated greyish-pink gland which has both endocrine and exocrine parts. Cells of exocrine part secrete pancreatic juice which contains enzymes like pancreatic amylase, trypsin and lipase that help in digestion of starch, proteins and fats, respectively. The cells of endocrine part secrete hormones glucagon and insulin that take part in glucose metabolism.
(c) (i)The absorption of digested food takes place in small intestine.
(ii) Absorption of most of the water from undigested food takes place in large intestine.
Question: (a) Draw a diagram of the human respiratory system and label on it: alveolar sac, bronchioles, larynx and trachea.
(b) How are the lungs designed in human beings to maximise the area of exchange of gases?
Answer:The labelled diagram of human respiratory system is as follows:
The primary organs of the respiratory system are lungs, which function to take in oxygen and expel carbon dioxide as we breathe. During the exchange of gases at the respiratory surface (alveoli) of the respiratory organs (lungs) and the oxygen enters the blood and combines with haemoglobin (respiratory pigment) of red blood corpuscles to form oxyhaemoglobin. The oxygenated blood from the lungs is carried to leftatrium of heart by pulmonary veins. The heart pumps and distributes the oxygenated blood to the body tissues by arteries where second exchange of gases occurs between blood and body cells. Blood gives oxygen to the body cells and takes carbon dioxide. Inside the cells,
oxygen is utilised for oxidation of simple nutrients to produce energy, carbon dioxide and water. Body cells give carbon dioxide to blood and deoxygenated blood is pumped to right atrium of heart from where pulmonary artery carries deoxygenated blood to lungs.
Question: (a) Draw a sectional view of the human heart and label on it: pulmonary arteries, vena cava, left ventricle.
(b) Why is double circulation of blood necessary in human beings?
Answer: (a) The sectional view of human heart is as follows:
(b)The blood passes through human heart twice for one supply to the body. One circulation involves the transport of deoxygenated blood from all body parts into the heart. This blood is transported to lungs for oxygenation. The second circulation involves entry of oxygenated blood from lungs into left side of the heart from where it is distributed to all parts of the body. Double circulation is made possible because the human heart is divided into two halves. One half umps deoxygenated blood to the lungs and the other half pumps oxygenated blood to the rest of the body.
Double circulation prevent any mixing of oxygenated and deoxygenated blood in the body ensuring maximum supply of oxygen to all body parts.This is necessary for humans who need a lot of energy to maintain their constant body temperature against any external temperature fluctuations. The rich oxygen supply enables optimum oxidation of glucose in body cells to release the required energy.
Question: Give one functional difference between RBC and WBC.
Answer:
Question: Why leaves become yellow in the absence of light?
Answer: Presence of light is quite necessary for plants because in presence of light plants by the process of photosynthesis synthesizes their food. In the absence of light the process of photosynthesis is not possible.
For synthesis of food presence of a pigment called chlorophyll is also necessary which absorbs the sunlight and helps in photosynthesis process. The colour of this pigment is green and therefore most of the plants exhibit green colour.
But when there will be no sunlight, no photosynthesis takes place and as plant will not get energy there will be no chlorophyll in the plant after some time and thus plant start becoming yellow in the absence of light.
Question: Why do the divers carry oxygen for artificial respiration?
Answer: The amount of dissolved oxygen in the water is quite low as compared to air which cannot fulfill the requirement of oxygen for breathing and hence affect the respiration process.
Specifically, underwater oxygen is available in dissolved form and humans cannot take in dissolved oxygen.
Therefore, in order to fulfil the requirement of oxygen for respiration process divers carry oxygen with them.
Question: Which cartilage of larynx forms “Adam’s apple” in man?
Answer: Thyroid cartilage of larynx forms Adam’s apple in man.
Question: Why is right kidney slightly lower in position compared to the left kidney?
Answer: Two kidneys are present in our body- one in left side and other on the right side respectively.
But the position of right kidney is slightly lower than the left kidney due to the presence of liver and large size of liver on the right side. To accommodate the size of liver the position of right kidney is slightly lower than the left kidney.
Following picture depicts the same thing explained above:
Question: What is normal breathing rate in an adult man at rest?
Answer: In an adult man at rest the normal breathing rate is 12 to 15 times per minute.
Question: Why is blood called a ‘liquid connective tissue’?
Answer: Blood is called a liquid connective tissue because blood consists of a liquid medium which is known as plasma and since it transports different gases, hormones, nutrients, enzymes to different parts of our body, blood establishes a connection between each cell of body.
Therefore, blood is called a liquid connective tissue.
Question: How are inspiration and expiration brought about in human beings?
Answer: Inspiration in human beings: Inspiration is the process in which we take the air inside the lungs. During this process the lifting of ribs and flattening of the diaphragm takes place. Due to this size of the thoracic cavity increases and pressure inside the lungs remain low as compared to atmospheric pressure and we inhale the air. This process is called inspiration.
Expiration in human beings: Expiration is the process in which we exhale the air outside our lungs. During this process relaxation of the lungs and diaphragm takes place. Due to this the size of thoracic cavity decreases and pressure inside the lungs is high as compared to atmospheric pressure and as a result we exhale the air outside the lungs. This process is called expiration.
Question: Bile juice does not contain any digestive enzymes, yet it is essential for digestion, why so? Explain.
Answer: Given statement is true that bile juice does not contain any digestive enzymes, yet it is essential for digestion.
Bile juice helps in the digestion of fats and lipids in an indirect way. When fats reach the small intestine, digestive enzymes are not able to act upon them because of their large globular size. So, the role of bile juice comes into existence over here. They break those large globular fat molecules into small molecules and this process is known as emulsification of fats. As, the large globular fat molecules are converted into small fat molecules digestive enzymes can now act on the fat globules and digestion of fats take place.
Therefore, bile juice helps in the digestion by the process of emulsification.
Question: Arrange the terms in correct sequence:
Glomerulus, renal vein, efferent arterioles, renal artery, afferent arterioles, secondary capillaries.
Answer: The correct sequence is as follows:
Afferent arteriole, Glomerulus, Efferent arteriole, Renal artery, Secondary capillaries, Renal vein
Question: Name two animals having cutaneous respiration. What special features of the skin make cutaneous respiration effective?
Answer: Frogs, snakes have cutaneous respiration.
Following are the special features of the skin that make cutaneous respiration effective:
•Moist and delicate nature of the skin makes the cutaneous respiration effective.
Question: If one hold his breath after expiration for about 30 sec., would there still be occurring any exchange of respiratory gases in the lung during this period?
Explain.
Answer: Yes, if someone holds his breath after expiration for about 30 sec there would still be occurring exchange of respiratory gases in the lungs during this period because after a normal expiration some amount of air remains in our lungs which we call as residual volume which is 1100-1200 ml. When we uphold our breath the exchange of this residual volume gases will continue in our lungs.
Question: Name two proteases in pancreatic juice. What are their specific roles?
Answer: Following are the two proteases in pancreatic juice:
•Trypsin: It helps in the digestion of proteins.
•Chymotrypsin: It helps in the breakdown of proteins into smaller molecules.
Question: Explain with a schematic representation the exchange of gases in tissues.
Answer: Following is the schematic representation of exchange of gases in tissues:
cardiopulmonary-system-diagram-diagram-of-the-cardiovascular-system-humancirculatory- system.jpg
First of all the gaseous exchange takes place between the alveoli and blood. Here the alveoli have great partial pressure of oxygen and less partial pressure of CO₂ while in blood the partial pressure of CO₂ is more and partial pressure of O₂ is less. So, exchange of gas takes place between blood and alveoli. The oxygen is transferred to blood and CO₂ is transferred to alveoli.
It is essential for plants because this process helps all parts of plant to receive the synthesised food, water and minerals and is essential for the survival of plant.
(i) Sugar is synthesised in leaves of the plant.
(ii) Hormones: There are various hormones secreted by plants. Therefore, there are various parts of plants which are associated with hormone synthesis like- Root tips, stems, young fruits, ripe fruits etc..
Question: Give a schematic diagram to show absorption of water through root hairs.
Answer: A schematic diagram showing absorption of water through roots is presented
below:
Question: Explain the various functions of blood.
Answer: Following are the functions associated with the blood:
•There is fluid portion in the blood which we call as plasma. It helps in the transportation of CO₂, food, nitrogenous wastes, hormones as they remain dissolved in the blood.
•Red blood cells remain present in blood and have great affinity for oxygen. It helps in the transportation of oxygen which remains bounded to Red blood cells.
•Blood also consists of White blood cells which helps person to fight against various diseases.
