Life Processes

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Photosynthesis is the process by which green plants and some other organisms use sunlight to synthesize nutrients from carbon dioxide and water. It involves the green pigment chlorophyll and generates oxygen as a by-product. This process is crucial for the survival of plants as it provides them with the energy needed for growth and development. For humans and other animals, photosynthesis is vital because it produces the oxygen we breathe and the food we eat. The general equation for photosynthesis is 6CO2 + 6H2O + light energy → C6H12O6 + 6O2. Without photosynthesis, the carbon cycle could not occur, oxygen-requiring life would not survive, and plants would die. Examples of photosynthesis can be seen in the growth of plants in sunlight compared to those kept in the dark. The process occurs in the chloroplasts of plant cells, where chlorophyll absorbs light energy. Photosynthesis also plays a key role in mitigating climate change by absorbing carbon dioxide, a greenhouse gas, from the atmosphere.

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The human digestive system is a complex process that involves the breakdown of food into smaller components that can be absorbed into the bloodstream. It starts in the mouth where food is chewed and mixed with saliva, which contains the enzyme amylase that begins the digestion of carbohydrates. The food then travels down the esophagus to the stomach, where gastric juices containing hydrochloric acid and the enzyme pepsin break down proteins. The small intestine is where most digestion and absorption occur, with enzymes from the pancreas and bile from the liver aiding in the breakdown of fats, proteins, and carbohydrates. The large intestine absorbs water and electrolytes, forming feces which are excreted through the rectum and anus. Enzymes play a crucial role in digestion by speeding up chemical reactions that break down food molecules into nutrients the body can use. For example, lipase breaks down fats into fatty acids and glycerol, while protease breaks down proteins into amino acids. Without these enzymes, digestion would be inefficient, leading to malnutrition and health problems.

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Aerobic respiration is the process of producing cellular energy involving oxygen. It is the most efficient form of respiration, producing up to 38 ATP molecules per glucose molecule. The equation for aerobic respiration is C6H12O6 + 6O2 → 6CO2 + 6H2O + energy. This type of respiration occurs in the mitochondria of cells and is used by most multicellular organisms, including humans, animals, and plants. Anaerobic respiration, on the other hand, does not require oxygen and produces less energy, only 2 ATP molecules per glucose molecule. It includes processes like fermentation, where glucose is broken down into lactic acid or ethanol and carbon dioxide. Examples of organisms that use anaerobic respiration include yeast, which produces alcohol and carbon dioxide during fermentation, and certain bacteria that live in oxygen-deprived environments like deep wounds or the gut. Some human muscle cells also resort to anaerobic respiration during intense exercise when oxygen supply is insufficient, leading to the production of lactic acid and muscle fatigue.

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The human circulatory system is responsible for transporting nutrients, oxygen, carbon dioxide, hormones, and blood cells to and from the cells in the body. It consists of the heart, blood vessels, and blood. The heart pumps blood through a network of arteries, veins, and capillaries. Arteries carry oxygenated blood away from the heart to the body, while veins return deoxygenated blood back to the heart. Capillaries are tiny vessels where the exchange of gases, nutrients, and waste products occurs between blood and tissues. The circulatory system is divided into two main loops: the pulmonary circulation, which carries blood to the lungs for oxygenation, and the systemic circulation, which delivers oxygenated blood to the body. Blood is composed of plasma, red blood cells, white blood cells, and platelets. Red blood cells contain hemoglobin, which binds oxygen, while white blood cells are part of the immune system. Platelets help in blood clotting. The circulatory system also plays a role in temperature regulation and the removal of waste products from the body.

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Excretion in human beings is the process of removing waste products of metabolism and other non-useful materials from the body. The primary organs involved are the kidneys, which filter blood to remove urea, excess salts, and water, forming urine. The kidneys contain millions of nephrons, the functional units that filter blood. Each nephron consists of a glomerulus, which filters blood, and a tubule, where reabsorption of useful substances like glucose and amino acids occurs. The urine formed is transported to the bladder via the ureters and expelled through the urethra. Besides the kidneys, the liver breaks down toxic substances like alcohol and drugs, the lungs excrete carbon dioxide, and the skin removes excess salts and water through sweat. The kidneys also regulate the body's fluid balance, electrolyte levels, and blood pressure. Without proper excretion, toxic substances would accumulate in the body, leading to conditions like uremia or kidney failure. Dialysis or kidney transplantation may be necessary in cases of kidney dysfunction.

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Plants and animals exhibit different modes of nutrition based on their ability to synthesize food. Plants are primarily autotrophic, meaning they can produce their own food through photosynthesis using sunlight, carbon dioxide, and water. Some plants, like the Venus flytrap, are heterotrophic to some extent, deriving nutrients by trapping insects. Animals, on the other hand, are heterotrophic, relying on other organisms for food. Herbivores eat plants, carnivores consume other animals, and omnivores eat both plants and animals. Parasitic organisms derive nutrition from living hosts, often harming them, while saprophytes feed on dead and decaying organic matter. Fungi and some bacteria are examples of saprophytes. Symbiotic nutrition involves a mutually beneficial relationship between two organisms, such as lichens, which are a partnership between fungi and algae. The mode of nutrition is closely linked to the organism's habitat, structure, and energy requirements, influencing its role in the ecosystem.

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The human respiratory system is responsible for the exchange of gases between the body and the environment. It consists of the nose, pharynx, larynx, trachea, bronchi, and lungs. Air enters through the nose, where it is filtered, warmed, and moistened. It then passes through the pharynx and larynx into the trachea, which divides into two bronchi, one leading to each lung. Inside the lungs, the bronchi branch into smaller bronchioles, ending in tiny air sacs called alveoli. The alveoli are surrounded by capillaries where the exchange of oxygen and carbon dioxide takes place through diffusion. Oxygen from the inhaled air passes into the blood, while carbon dioxide, a waste product of metabolism, is expelled during exhalation. The diaphragm and intercostal muscles play a crucial role in breathing by expanding and contracting the chest cavity. The respiratory system also helps regulate blood pH by controlling the levels of carbon dioxide in the blood. Smoking and pollution can damage the respiratory system, leading to diseases like asthma, bronchitis, and lung cancer.

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Plants transport water and minerals from the roots to the leaves through a vascular tissue called xylem. The process begins at the roots, where root hairs absorb water and minerals from the soil by osmosis and active transport. The water and minerals then move into the xylem vessels, which are long, hollow tubes made of dead cells. The movement of water upward is facilitated by transpiration, the evaporation of water from the leaves, which creates a suction pull. Cohesion and adhesion forces also play a role, as water molecules stick to each other and to the walls of the xylem vessels. Minerals are dissolved in the water and transported along with it to various parts of the plant. This transport is essential for photosynthesis, as water is a raw material, and minerals are needed for various metabolic processes. The rate of transpiration is influenced by environmental factors like temperature, humidity, and wind speed. Plants can regulate water loss by opening and closing stomata, the pores on leaves.

Solution

Hemoglobin is a protein found in red blood cells that is crucial for transporting oxygen from the lungs to the rest of the body and carrying carbon dioxide back to the lungs for exhalation. Each hemoglobin molecule can bind four oxygen molecules, enabling efficient oxygen transport. The iron in hemoglobin gives blood its red color and binds oxygen in the lungs, forming oxyhemoglobin. In the tissues, where oxygen levels are low, hemoglobin releases oxygen, which is then used for cellular respiration. Hemoglobin also helps maintain the shape of red blood cells, allowing them to move easily through blood vessels. A deficiency of hemoglobin, known as anemia, can lead to fatigue, weakness, and shortness of breath due to insufficient oxygen delivery to tissues. Hemoglobin levels can be affected by factors like diet, especially iron intake, and certain diseases. Carbon monoxide poisoning occurs when hemoglobin binds to carbon monoxide more strongly than oxygen, preventing oxygen transport. Hemoglobin also plays a role in regulating blood pH by binding to hydrogen ions.

Solution

Double circulation in humans refers to the two separate circuits through which blood travels: the pulmonary circulation and the systemic circulation. In pulmonary circulation, deoxygenated blood is pumped from the right ventricle of the heart to the lungs via the pulmonary arteries. In the lungs, blood picks up oxygen and releases carbon dioxide, then returns to the left atrium of the heart through the pulmonary veins. In systemic circulation, oxygenated blood is pumped from the left ventricle to the rest of the body via the aorta and its branches. After delivering oxygen and nutrients to tissues, the now deoxygenated blood returns to the right atrium through the superior and inferior vena cava. Double circulation ensures that oxygenated and deoxygenated blood do not mix, increasing the efficiency of oxygen delivery to tissues. This is particularly important for warm-blooded animals like humans, which have high metabolic rates and require a constant supply of oxygen. The separation of the two circuits also allows for higher blood pressure in systemic circulation, ensuring that all body tissues receive adequate blood flow. The heart's four-chambered structure is key to this efficient separation and circulation.

Solution

Photosynthesis is the process by which green plants and some bacteria convert light energy into chemical energy, using chlorophyll to absorb sunlight. The process involves the conversion of carbon dioxide and water into glucose and oxygen. Desert plants have adapted to perform photosynthesis at night to minimize water loss, storing carbon dioxide as an intermediate for use during the day.

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Aerobic respiration requires oxygen and produces carbon dioxide, water, and a large amount of energy. Anaerobic respiration does not require oxygen and produces less energy, along with byproducts like ethanol or lactic acid. Humans use aerobic respiration, while yeast undergoes anaerobic respiration to produce ethanol.

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The journey begins in the mouth where salivary amylase breaks down starch. Food then moves to the stomach where pepsin digests proteins. In the small intestine, bile emulsifies fats, and pancreatic enzymes further break down nutrients. Absorption occurs in the villi, and undigested food is egested through the large intestine.

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Alveoli have thin walls and a large surface area surrounded by capillaries, facilitating efficient gas exchange. Nephrons filter blood to remove wastes and reabsorb needed substances, both structures maximize efficiency through their design—alveoli for gas exchange and nephrons for filtration and reabsorption.

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Double circulation involves two pathways: pulmonary circulation (heart to lungs and back) and systemic circulation (heart to body and back). This ensures that oxygenated and deoxygenated blood do not mix, providing efficient oxygen delivery to tissues.

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Xylem transports water and minerals from roots to leaves using dead cells, while phloem transports food from leaves to other parts using living cells. Xylem provides mechanical support, whereas phloem does not.

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Kidneys filter blood to remove wastes like urea, regulate water and electrolyte balance, and maintain pH. Urine formation involves glomerular filtration, reabsorption of useful substances, and secretion of wastes.

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Plants excrete waste through transpiration, storing wastes in leaves that fall off, or as resins and gums. Humans excrete through specialized organs like kidneys, which filter blood to remove nitrogenous wastes.

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Haemoglobin in red blood cells binds oxygen for transport to tissues. Deficiency leads to anemia, causing fatigue and weakness due to inadequate oxygen delivery.

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The experiment involves placing a plant in a bell jar with potassium hydroxide to absorb CO2, showing no starch formation without CO2. The control would be a similar setup without potassium hydroxide, allowing normal photosynthesis.

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Autotrophic nutrition relies on photosynthesis, which requires sunlight. In the dark, the plant uses up its starch reserves, affecting its energy supply. Upon exposure to sunlight, the plant resumes photosynthesis, but the initial lack of energy could impact growth and health.

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Hemoglobin binds oxygen in the lungs and releases it in tissues. Deficiency leads to anemia, causing fatigue and reduced oxygen delivery to cells, impacting metabolism and overall health.

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Aerobic respiration produces more ATP (36-38 molecules) and by-products are CO2 and water. Anaerobic produces less ATP (2 molecules) and by-products like lactic acid or ethanol and CO2.

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Double circulation ensures complete separation of oxygenated and deoxygenated blood, increasing efficiency. Fish have single circulation, where blood passes through the heart once per cycle, making it less efficient.

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Nephrons filter blood, reabsorb useful substances, and excrete wastes. The glomerulus filters small molecules, while the tubule reabsorbs nutrients and water, concentrating wastes in urine.

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Transpiration pulls water upwards through xylem due to evaporation from leaves, creating a suction force. This also facilitates mineral transport from roots to other parts.

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Smoking damages alveoli, reducing gas exchange efficiency, and paralyzes cilia, leading to mucus buildup and increased infection risk, such as lung cancer.

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Bile emulsifies fats, increasing enzyme action surface area. Its deficiency leads to poor fat digestion and absorption, causing deficiencies and digestive issues.

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The small intestine has villi and microvilli increasing surface area, thin epithelial layers for quick diffusion, and blood capillaries for nutrient transport.

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Plants store wastes in vacuoles, leaves (shed), or as resins/gums. They lack specialized excretory organs, using passive methods like diffusion and transpiration.