10th Grade Science Life Processes: Access Ncert Solutions for Free

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  The inner lining of the small intestine undergoes a transformation into tiny finger-like projections known as villi that enhance the surface area for the absorption of digested food. These villi are abundantly supplied with blood vessels, making them highly vascularized. Additionally, the villi contain lactease, which aids in the absorption of digested fats.

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  Aquatic organisms depend on the dissolved oxygen in water. However, since the solubility of oxygen in water is limited, the availability of oxygen for these organisms is insufficient. As a result, they need to respire at a faster rate. Conversely, terrestrial animals obtain oxygen directly from the atmosphere, resulting in a comparatively lower respiration rate.

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  The utilization of glucose for energy production relies on the presence of oxygen. In the presence of oxygen, glucose undergoes aerobic breakdown in mitochondria, while in the absence of oxygen, it undergoes anaerobic breakdown in the cytoplasm, resulting in a relatively lower energy yield. Aerobic respiration involves the complete oxidation of food in the presence of oxygen, resulting in the production of CO2, H2O, and a large amount of energy. On the other hand, anaerobic respiration is an incomplete oxidation process that occurs in the absence of oxygen. For instance, during intense physical exertion, skeletal muscles respire without oxygen for a certain period to generate additional energy. This partial breakdown of glucose produces CO2, ethyl alcohol, lactic acid, and energy.

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  Hemoglobin, located in red blood cells, exhibits a high affinity for oxygen. It temporarily combines with oxygen to form oxyhemoglobin, facilitating the transportation of oxygen from the lungs to various body parts. Carbon dioxide (CO2) is highly soluble in water, which allows it to be primarily transported in a dissolved state within the blood plasma.

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  Within the lungs, the bronchus branches out into smaller and smaller tubes called bronchioles, ultimately terminating in balloon-like structures referred to as alveoli. These alveoli consist of thin, moist membranes that are abundantly supplied with blood, thereby providing an extensive surface area for the exchange of gases. It is worth mentioning that if the alveolar surface could be expanded, it would cover an area of approximately 80 square meters.

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  The transportation systems of animals and plants exhibit a variety of characteristics. 1.   Transportation in human beings The human transport system comprises blood, heart, blood vessels, and lymph. Blood, containing O2, CO2 salts, and nutrients, performs the task of transporting these substances throughout the body. The heart collects deoxygenated blood from different body parts and pumps oxygenated blood. Arteries, veins, and capillaries serve as blood vessels. While arteries carry blood away from the heart, veins collect blood from different organs. The exchange of materials between the blood and surrounding cells occurs through the thin capillary walls. In addition, lymph, another form of fluid, contributes to transportation by carrying digested and absorbed fat from the intestine and draining excess fluid from the extracellular space into the blood. 2.   Transportation in Plants Plant transport systems involve the movement of energy stores from leaves and essential materials from the roots. The plant transport system consists of xylem and phloem. Xylem is responsible for transporting water and minerals obtained from the soil, whereas phloem transports the products of photosynthesis from the synthesis site to other parts of the plant.

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  Birds and mammals have tissues with high metabolic rates, necessitating the rapid delivery of oxygenated, nutrient-rich blood. This is achieved through the maintenance of high blood pressure. Birds and mammals achieve this through double circulation, which involves the separation of oxygenated and deoxygenated blood.

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  Plant transport systems in highly organized plants facilitate the movement of energy stores from leaves and raw materials from roots. These pathways are constructed as independent organized conducting tubes, specifically composed of xylem and pholem. (i) The xylem transports water and minerals from the roots to the leaves and other parts of the plant. (ii) The phloem, on the other hand, transports the products of photosynthesis from the leaves to other plant parts, including the roots.

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  The vessels and tracheids within the xylem tissue of the root, stem, and leaves are interconnected, forming a continuous water conducting channel that reaches all parts of the plant. The cells in the root that are in contact with the soil actively take up ions. To equalize the concentration difference between the root and soil, water moves into the root from the soil. Transpiration, the evaporation of water molecules from the leaf cells, creates a suction force that pulls water from the xylem cells of the roots. Consequently, transportation aids in the absorption and upward movement of water and minerals from the roots to the leaves.

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  The movement of soluble products resulting from the process of photosynthesis is referred to as translocation. This process takes place through the phloem, which is responsible for transporting not only the products of photosynthesis but also amino acids and other substances. Translocation occurs within the sieve tubes, aided by neighboring companion cells in both upward and downward directions. To transfer materials like sucrose, the phloem tissue utilizes ATP, resulting in an increase in the osmotic pressure of the tissue. This, in turn, causes water to move into the tissue, generating pressure that propels the material within the phloem to areas with lower pressure. This unique mechanism enables the phloem to transport materials according to the plant's requirements.

  Kidneys consist of numerous excretory units known as nephrons. Each nephron comprises a cup-shaped structure called Bowman's capsule at its upper end, with a U-shaped tube known as the tubule at its lower end. Together, the Bowman's capsule and tubule constitute the nephron. One end of the tubule is connected to the Bowman's capsule, while the other end is linked to a urine-collecting duct within the kidney. Within the Bowman's capsule, there is a cluster of blood capillaries called the glomerulus. The glomerulus is connected to the renal artery, through which blood containing urea waste enters. The other end of the glomerulus exits the Bowman's capsule, with blood capillaries surrounding the tubule and eventually joining a renal vein. The main function of the glomerulus is to filter blood as it flows through it. During ultrafiltration, small molecules such as glucose, water, amino acids, and minerals pass through, while blood cells and proteins are retained. As the filtrate travels down the tubule, valuable substances like glucose, amino acids, and a majority of the water are reabsorbed by capillaries surrounding the tubule. However, waste materials like urea remain within the tubule, forming urine. The nephron carries urine into the collecting duct of the kidney, from where it is transported to the ureter.

  Plants eliminate excess water through transpiration, while other waste materials are discharged through dead cells or the shedding of certain plant parts, such as leaves. Many waste products in plants are stored in vacuoles within cells. Additionally, some waste substances are stored as resins and gums in old xylem. Plants also excrete certain waste products into the surrounding soil.

  The volume of urine produced is regulated by the hormone anti-diuretic hormone (ADH), which is secreted by the anterior pituitary gland. If the blood contains an excess of water, a diluted urine is excreted, indicating that less water is reabsorbed and a larger amount is expelled. Conversely, if the blood has a low water content, concentrated urine is excreted. This phenomenon is known as osmoregulation.

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                  (c) This option is incorrect because autotrophs can only convert carbon dioxide and water into carbohydrates with the presence of sunlight. Autotrophs have a green pigment called chlorophyll, which can capture solar energy. This energy is used by autotrophs to create their food through the process of photosynthesis. Any unused food is stored as starch. Autotrophs are the first trophic level in food chains.

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                    (b) Organisms such as yeast, mushroom, and bread mold are saprophytes. They break down complex organic molecules found in dead or decaying matter into simpler substances outside their bodies. These simpler substances are then absorbed by saprophytes through saprotrophic nutrition. Green plants, on the other hand, are autotrophic and can produce their own food through photosynthesis. Amoeba and Paramecium have holozoic nutrition, consuming solid or liquid organic food. Meanwhile, organisms like Cuscuta, lice, and tapeworm are parasitic and obtain their food from the bodies of their hosts.

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                    (a) Heterotrophs are organisms that cannot produce their own food from inorganic substances like carbon dioxide and water since they lack chlorophyll to capture solar energy. Examples of heterotrophs include animals, most bacteria, and fungi. These organisms rely on other organisms for their food. Autotrophs, such as green plants, synthesize their own food through photosynthesis by using solar energy.

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                    (d) The sequence of organs involved in human nutrition are mouth, esophagus, stomach, small intestine, large intestine, and anus. The digestive system in human beings consists of the alimentary canal and associated glands, through which nutrition takes place.

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                    (b) Human saliva contains an enzyme called salivary amylase, which breaks down starch into sugar during the process of digestion. The breakdown of starch begins in the mouth. If there is a lack of saliva, it can affect the breakdown of starch. Protein digestion starts in the stomach with the enzyme pepsin and completes in the small intestine with enzymes like trypsin, chymotrypsin, carboxy peptidases, amino peptidases, and dipeptidases. Fats are broken down into small particles by bile in the small intestine and further broken down into fatty acids and glycerol by lipases present in pancreatic juice. Lastly, the absorption of vitamins occurs in the small intestine.

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    (b) The mucus in the gastric juice is secreted by the stomach wall's glands. Its purpose is to safeguard the stomach wall against the corrosive effects of hydrochloric acid. Without mucus secretion, hydrochloric acid would erode the inner lining of the stomach, potentially causing ulcers. Pepsin is responsible for protein breakdown in the stomach. Saliva contains salivary amylase, which acts on starch in the mouth. Bile aids in fat emulsification in the small intestine.

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    (a) Stomach

    (b) Small intestine

    (c) Large intestine

    (d) Esophagus

    (b) The small intestine receives bile from the liver, which is typically stored in the gall bladder. It serves two functions: alkalizing the food and breaking down fats into small globules through emulsification.

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    (d) The presence of starch is confirmed by the blue-black color of rice water when iodine is added. There will be no change in color when proteins or fats are combined with iodine solution.

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    (d) The small intestine is where complete food digestion occurs in human beings. It is also the primary site of nutrient absorption. While digestion initiates in the oral cavity and continues in the stomach, forming a semi-solid paste, the remaining undigested food from the small intestine moves into the large intestine, where water absorption takes place.

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    (d) The pancreas secretes pancreatic juice containing the following digestive enzymes: amylases, lipases, and trypsin. Amylase breaks down starch, trypsin digests proteins, and lipase breaks down emulsified fats.

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    (b) Lime water turns milky when exposed to carbon dioxide gas. Blowing air from the mouth into a test tube causes the lime water to turn milky because our exhaled breath contains higher levels of CO2.

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    (d) The process of transforming glucose into pyruvate (known as glycolysis) occurs within the cytoplasm of the cell. This marks the initial stage of respiration. Subsequently, the conversion of pyruvate into various compounds is determined by the presence or absence of oxygen. Different pathways are involved in the breakdown of glucose.

  

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    (b) Aerobic respiration, unlike anaerobic respiration, necessitates the utilization of oxygen and transpires within the mitochondria. Following glycolysis, pyruvate (originating from the cytoplasm) enters the mitochondria and undergoes a series of reactions, resulting in the oxidation of pyruvate. This process generates a substantial amount of energy in the form of ATP, along with the production of CO2 and H2O.

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