Class 10 Science Chapter 5 Assertion and Reason Questions - Life Processes

Question 1: 
Assertion: Muscles of the stomach wall possess thick layers of muscles. 

Reason: These muscles help in mixing the food with the enzymes present in the alimentary canal. 

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
(e) Both Assertion and Reason are false.

Correct Answer: (a) Both A and R are true and R is the correct explanation of A.

Explanation:
The assertion is true because the stomach wall indeed has thick layers of muscles, which aid in mixing food with digestive enzymes through muscular contractions (peristalsis). The reason correctly explains that these muscular movements facilitate the mechanical breakdown of food and its mixing with digestive enzymes, preparing it for further digestion in the alimentary canal.

Question 2: 

Assertion: Respiration is a biochemical process opposite to photosynthesis. 

Reason: Energy is released during respiration. 

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
(e) Both Assertion and Reason are false.

Correct Answer: (a) Both A and R are true and R is the correct explanation of A.

Explanation: Respiration and photosynthesis are indeed biochemical processes that are opposite to each other. Respiration involves the breakdown of organic molecules to release energy, whereas photosynthesis uses light energy to synthesize organic molecules. The reason is correct because energy (in the form of ATP) is released during respiration, facilitating various cellular processes and activities.

Question 3: 

Assertion: In plants, there is no need for specialized respiratory organs. 

Reason: Plants do not have great demands for gaseous exchange. 

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
(e) Both Assertion and Reason are false.

Correct Answer: (a) Both A and R are true and R is the correct explanation of A.

Explanation: The assertion is true because plants do not possess specialized organs like lungs or gills for gaseous exchange; instead, they rely on diffusion through stomata and lenticels. The reason correctly explains this by stating that plants have lower metabolic rates compared to animals, leading to lower demands for gaseous exchange. Diffusion through stomata and lenticels is sufficient to meet their needs.

Question 4: 

Assertion: The walls of the intestine have numerous villi. 

Reason: These villi increase the surface area for digestion. 

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
(e) Both Assertion and Reason are false.

Correct Answer: (c) A is true but R is false.

Explanation: The assertion is true because the walls of the intestine are lined with numerous finger-like projections called villi, which significantly increase the surface area available for absorption, not digestion. The reason is incorrect because villi primarily aid in absorption, not digestion itself. They increase the efficiency of nutrient absorption by providing a larger surface area for contact with digested food molecules.

Question 5: 

Assertion: Blood pressure refers to arterial blood pressure. 

Reason: It is measured by a sphygmomanometer. 

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
(e) Both Assertion and Reason are false.

Correct Answer: (b) Both A and R are true but R is not the correct explanation of A.

Explanation: The assertion is true because blood pressure typically refers to arterial blood pressure, which is the pressure exerted on the walls of arteries during blood circulation. The reason is also true because blood pressure is measured using a sphygmomanometer. However, measuring blood pressure with a sphygmomanometer does not explain why blood pressure specifically refers to arterial pressure; it is a method of measurement rather than an explanation of the term.

Question 6: 

Assertion: The main organ of the human excretory system is the kidney. 

Reason: Kidneys perform the function of removing excess water and nitrogenous wastes from the body. 

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
(e) Both Assertion and Reason are false.

Correct Answer: (a) Both A and R are true and R is the correct explanation of A.

Explanation: The assertion is true because the kidneys are indeed the primary organs responsible for filtering blood, removing waste products (like urea and excess water), and regulating electrolyte balance. The reason correctly explains this function of the kidneys, emphasizing their role in maintaining homeostasis by filtering blood and excreting waste products in the form of urine.

Question 7: 

Assertion: Humans are aerobically respiring organisms. 

Reason: They produce lactic acid anaerobically. 

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
(e) Both Assertion and Reason are false.

Correct Answer: (b) Both A and R are true but R is not the correct explanation of A.

Explanation: The assertion is true because humans primarily respire aerobically, using oxygen to break down glucose and produce energy (ATP). The reason is also true because in certain conditions, such as during intense exercise, skeletal muscles can undergo anaerobic respiration, producing lactic acid. However, lactic acid production does not explain why humans are primarily aerobic; it illustrates a specific circumstance where anaerobic respiration occurs as a backup energy source.

Question 8: 

Assertion: HCl converts pepsinogen into the active enzyme pepsin. 

Reason: Pepsin converts proteins into proteoses and peptones. 

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
(e) Both Assertion and Reason are false.

Correct Answer: (b) Both A and R are true but R is not the correct explanation of A.

Explanation: The assertion is true because HCl (hydrochloric acid) in the stomach activates pepsinogen to pepsin, an enzyme essential for protein digestion. The reason is also true because pepsin, once activated, breaks down proteins into smaller peptides called proteoses and peptones. However, the conversion of pepsinogen to pepsin by HCl does not directly explain the subsequent enzymatic action of pepsin on proteins; it describes two separate steps in the process of protein digestion.

Question 9: 

Assertion: Hemoglobin is the respiratory pigment in human beings. 

Reason: It transports oxygen in the human body. 

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
(e) Both Assertion and Reason are false.

Correct Answer: (a) Both A and R are true and R is the correct explanation of A.

Explanation: The assertion is true because hemoglobin, found in red blood cells, is indeed the respiratory pigment responsible for transporting oxygen from the lungs to tissues and carbon dioxide from tissues to the lungs. The reason correctly explains this function of hemoglobin, highlighting its role in oxygen transport through reversible binding with oxygen molecules in the lungs and release of oxygen in tissues where it is needed.

Question 10: 

Assertion: Blood of insects is colorless. 

Reason: The blood of insects does not play any role in the transport of oxygen. 

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
(e) Both Assertion and Reason are false.

Correct Answer: (b) Both A and R are true but R is not the correct explanation of A.

Explanation: The assertion is true because the blood (hemolymph) of insects is typically colorless or pale yellow due to the absence of hemoglobin, which is responsible for the red color of vertebrate blood. The reason is also true because hemolymph in insects primarily functions in nutrient transport rather than oxygen transport; insects use a system of tracheal tubes for oxygen distribution. However, the colorlessness of insect blood does not directly explain its role in oxygen transport, making option (b) the correct choice.

Question 11: 

Assertion: Human body produces highly toxic substances, which if not eliminated may cause death. 

Reason: Excretory system removes nitrogenous waste from the body. 

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
(e) Both Assertion and Reason are false.

Correct Answer: (b) Both A and R are true but R is not the correct explanation of A.

Explanation: The assertion is true because the human body produces metabolic waste products like urea, ammonia, and uric acid that can be toxic if accumulated. The reason is also true because the excretory system, including the kidneys, plays a crucial role in removing these nitrogenous wastes from the bloodstream. However, while the reason explains a function of the excretory system, it does not directly relate to why the substances are highly toxic if not eliminated, making option (b) the correct choice.

Question 12: 

Assertion: Liver is known as the smallest gland of the body. 

Reason: It secretes salivary amylase. 

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
(e) Both Assertion and Reason are false.

Correct Answer: (e) Both Assertion and Reason are false.

Explanation: Both the assertion and reason are incorrect. The liver is not the smallest gland; it is actually the largest internal organ in humans responsible for detoxification, protein synthesis, and various metabolic functions, but it does not secrete salivary amylase. Salivary amylase is secreted by the salivary glands in the mouth to begin the digestion of starches. Therefore, option (e) is the correct choice as both parts of the statement are false.

Question 13: 

Assertion: Valves are present in the arteries. 

Reason: Arteries carry oxygenated blood from the heart to different body parts except the pulmonary artery. 

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
(e) Both Assertion and Reason are false.

Correct Answer: (d) A is false but R is true.

Explanation: The assertion is false because valves are not present in arteries; they are present in veins to prevent backflow of blood. The reason is true because arteries do carry oxygenated blood from the heart to various parts of the body, except for the pulmonary artery, which carries deoxygenated blood from the heart to the lungs for oxygenation. Therefore, option (d) is the correct choice because the assertion is false while the reason is true.

Question 14: 

Assertion: Hemodialysis can save the life of patients with kidney failure. 

Reason: Waste products like urea can be removed from the blood by hemodialysis. 

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
(e) Both Assertion and Reason are false.

Correct Answer: (a) Both A and R are true and R is the correct explanation of A.

Explanation: The assertion is true because hemodialysis is a life-saving procedure for patients with kidney failure, where an artificial kidney machine filters waste products like urea from the blood when the kidneys can no longer perform this function effectively. The reason correctly explains why hemodialysis is necessary and how it functions. Therefore, option (a) is the correct choice as both the assertion and the reason are true, and the reason explains the assertion.

Question 15: 

Assertion: Photosynthesis is an anabolic process. 

Reason: The process of photosynthesis occurs in chlorophyll. 

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
(e) Both Assertion and Reason are false.

Correct Answer: (c) A is true but R is false.

Explanation: The assertion is true because photosynthesis is indeed an anabolic process where carbon dioxide and water are converted into glucose and oxygen using light energy. The reason is false because chlorophyll is a pigment found in chloroplasts that absorbs light energy for photosynthesis; photosynthesis itself occurs in the chloroplasts, not specifically in chlorophyll. Therefore, option (c) is the correct choice as the assertion is true while the reason is false.

Question 16: 

Assertion: Alveoli contain an extensive network of blood vessels. 

Reason: Alveoli is the site where exchange of gases occurs. 

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
(e) Both Assertion and Reason are false.

Correct Answer: (a) Both A and R are true and R is the correct explanation of A.

Explanation: The assertion is true because alveoli are tiny air sacs in the lungs that are surrounded by a dense network of capillaries, facilitating the exchange of gases (oxygen and carbon dioxide) between the lungs and the bloodstream. The reason correctly explains why alveoli have this network of blood vessels, emphasizing their role as the primary site of gas exchange in the lungs. Therefore, option (a) is the correct choice as both parts of the statement are true, and the reason explains the assertion.

Question 17: 

Assertion: Plants excrete various waste products during their life processes. 

Reason: They produce urea just like humans. 

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
(e) Both Assertion and Reason are false.

Correct Answer: (c) A is true but R is false.

Explanation: The assertion is true because plants do excrete various waste products such as resins, latex, and volatile organic compounds as part of their metabolic processes. However, the reason is false because plants do not produce urea as a waste product; urea is a nitrogenous waste product specific to animals, including humans, produced in the liver during protein metabolism and excreted through urine. Therefore, option (c) is the correct choice as the assertion is true while the reason is false.

Question 18: 

Assertion: Bile is essential for the digestion of lipids. 

Reason: Bile juice contains enzymes. 

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
(e) Both Assertion and Reason are false.

Correct Answer: (b) Both A and R are true but R is not the correct explanation of A.

Explanation: The assertion is true because bile, produced by the liver and stored in the gallbladder, is essential for the digestion and absorption of lipids (fats) in the small intestine by emulsifying fat globules into smaller droplets, increasing their surface area for enzymatic digestion. The reason is also true because bile juice does contain bile salts, which aid in the emulsification process, but it does not contain enzymes for lipid digestion itself. Therefore, option (b) is the correct choice as both parts of the statement are true, but the reason does not directly explain the assertion.

Question 19: 

Assertion: In humans, there is a complex respiratory system. 

Reason: Human skin is impermeable to gases. 

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
(e) Both Assertion and Reason are false.

Correct Answer: (b) Both A and R are true but R is not the correct explanation of A.

Explanation: The assertion is true because humans have a complex respiratory system that includes specialized organs like the lungs, bronchi, and alveoli to facilitate efficient gas exchange. The reason is also true because human skin is indeed impermeable to gases, requiring the respiratory system to facilitate gas exchange through the lungs. However, the impermeability of human skin to gases does not directly explain why humans have a complex respiratory system. Therefore, option (b) is the correct choice as both parts of the statement are true, but the reason does not explain the assertion.

Question 20: 

Assertion: In humans, the major amount of water is absorbed by the tubular part of the nephron. 

Reason: Absorption of water depends on the dissolved waste to be excreted from the body. 

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
(e) Both Assertion and Reason are false.

Correct Answer: (b) Both A and R are true but R is not the correct explanation of A.

Explanation: The assertion is true because the majority of water reabsorption in the kidney occurs in the tubular part of the nephron, specifically the proximal convoluted tubule and the collecting ducts. The reason is also true because the reabsorption of water in the nephron is regulated by hormones like antidiuretic hormone (ADH) and aldosterone, which respond to the body's hydration status and electrolyte balance rather than the dissolved waste products alone. Therefore, option (b) is the correct choice as both parts of the statement are true, but the reason does not explain the assertion directly.