Science Knowledge - 4 - Year 5 MCQ

Role of Calcium in Blood Coagulation:
- Calcium is an essential nutrient that plays a crucial role in the coagulation or clotting of blood.
- It is required for the activation of several clotting factors, including factor XIII, factor IX, factor X, and prothrombin.
- Calcium ions act as cofactors in the coagulation cascade, promoting the conversion of prothrombin to thrombin, which is responsible for the formation of fibrin clot.
- Without adequate calcium, the blood clotting process would be impaired, leading to prolonged bleeding or difficulty in stopping bleeding.
- Calcium is also important in maintaining the stability and integrity of the clot by promoting the cross-linking of fibrin strands.
Other Nutrients:
- Iron: Iron is essential for the production of hemoglobin, a protein in red blood cells that carries oxygen. While iron is important for overall blood health, it does not directly play a role in blood coagulation.
- Potassium: Potassium is involved in regulating fluid balance and maintaining proper cellular function, but it does not have a direct impact on blood coagulation.
- Sodium: Sodium is important for maintaining fluid balance and nerve function but does not have a direct role in blood coagulation.
In summary, calcium is the nutrient that plays a crucial role in the coagulation of blood. It is necessary for the activation of clotting factors and the formation of a stable fibrin clot.

Answer:
The vitamin that can be synthesized by the human body is Vitamin D. Here is a detailed explanation:
Vitamin D synthesis:
- Vitamin D is a unique vitamin as it can be synthesized by the human body through exposure to sunlight.
- When the skin is exposed to ultraviolet B (UVB) radiation from the sun, a precursor molecule called 7-dehydrocholesterol present in the skin is converted into cholecalciferol, which is an inactive form of Vitamin D.
- Cholecalciferol then undergoes further metabolic processes in the liver and kidneys to be converted into its active form, called calcitriol.
Importance of Vitamin D:
- Vitamin D plays a crucial role in maintaining bone health as it helps in the absorption and utilization of calcium and phosphorus.
- It is also involved in regulating the immune system and reducing the risk of various diseases such as osteoporosis, certain types of cancer, and autoimmune disorders.
- Adequate levels of Vitamin D are essential for overall health and well-being.
Sources other than sunlight:
- Although sunlight is the primary source of Vitamin D synthesis in the body, it can also be obtained from certain food sources such as fatty fish (salmon, mackerel), egg yolks, and fortified dairy products.
- However, the amount of Vitamin D obtained from diet alone is usually insufficient to meet the body's requirements, making sunlight exposure crucial.
Overall, while Vitamin D can be synthesized by the human body, it is important to ensure adequate sunlight exposure and, if necessary, obtain Vitamin D from dietary sources or supplements to maintain optimal levels for overall health.

Process responsible for producing photons in a diode laser:
- Electron-hole recombination: This is the correct answer. The process responsible for producing photons in a diode laser is electron-hole recombination. When a forward bias voltage is applied to a diode laser, electrons from the n-type region and holes from the p-type region are injected into the active region of the diode. These injected electrons and holes recombine with each other, releasing energy in the form of photons.
- Fermi level shift: This is not the correct answer. Fermi level shift refers to the shift in the Fermi energy level in a semiconductor due to the presence of impurities or doping. It does not directly produce photons in a diode laser.
- Majority carrier injection: This is not the correct answer. Majority carrier injection refers to the injection of majority charge carriers (electrons in n-type and holes in p-type) into the active region of a diode. While this process is important for the operation of a diode laser, it does not directly produce photons.
- Carrier freeze out: This is not the correct answer. Carrier freeze out refers to a condition in a semiconductor where the majority charge carriers are depleted due to a decrease in temperature. It does not produce photons in a diode laser.
In conclusion, the correct process responsible for producing photons in a diode laser is electron-hole recombination. When electrons and holes recombine in the active region of the diode, energy is released in the form of photons, resulting in laser emission.

The variety of coal that contains the highest percentage of carbon is Anthracite. Here's a detailed explanation:
Anthracite:
- Anthracite is the highest rank of coal and is known for its high carbon content, low moisture content, and high energy density.
- It is a hard and brittle coal that has undergone the most metamorphosis compared to other coal varieties.
- Anthracite is formed from the compression and heating of bituminous coal over millions of years.
- It has a carbon content of 86-97%, making it the coal variety with the highest percentage of carbon.
- Due to its high carbon content, anthracite has the highest energy content and burns with a clean flame and little smoke.
- It is mainly used for residential and commercial heating, as well as in industrial processes that require high heat and energy.
Other Coal Varieties:
- Peat: Peat has the lowest carbon content among coal varieties, typically ranging from 45-55%.
- Bituminous: Bituminous coal has a carbon content ranging from 45-86%. It is widely used for electricity generation and industrial processes.
- Lignite: Lignite has a carbon content ranging from 25-35%. It is a low-grade coal with high moisture content and is primarily used for electricity generation.
In conclusion, anthracite coal contains the highest percentage of carbon, making it a valuable energy resource due to its high energy content and clean-burning properties.

Main Component of Biogas and Natural Gas: Methane

• Biogas: Biogas is a renewable energy source produced through the anaerobic digestion of organic matter such as agricultural waste, sewage sludge, and food waste. The main component of biogas is methane, which typically makes up around 50-75% of its composition.


• Natural Gas: Natural gas is a fossil fuel formed from the remains of ancient plants and animals over millions of years. It is primarily composed of methane, with other hydrocarbons and trace amounts of impurities. Methane accounts for around 70-90% of the composition of natural gas.

Key Points:
- The main component of both biogas and natural gas is methane.
- Methane is a greenhouse gas and has a high energy content, making it a valuable fuel source.
- Biogas is produced through the decomposition of organic matter in an oxygen-free environment, such as a biogas digester.
- Natural gas is extracted from underground reserves and can be found alongside petroleum deposits or in standalone gas fields.
- Both biogas and natural gas can be used for heating, cooking, electricity generation, and as a fuel for vehicles.
- Biogas is considered a renewable energy source, as it is produced from organic waste materials that would otherwise release methane into the atmosphere.
- Natural gas is a non-renewable energy source, as it is formed over geologic timescales and its extraction depletes finite reserves.
By understanding the main component of biogas and natural gas, we can better appreciate their importance as energy sources and their impact on the environment.

Dry Ice: Solid Carbon Dioxide
Dry ice is the solid form of carbon dioxide, a gas. It is called "dry ice" because it does not melt into a liquid when heated; instead, it undergoes sublimation, directly changing from a solid to a gas. Here are some key points to understand about dry ice:
1. Composition:
- Dry ice is made up of carbon dioxide molecules arranged in a solid lattice structure.
- It is produced by compressing and cooling carbon dioxide gas to a temperature below -78.5 degrees Celsius (-109.3 degrees Fahrenheit).
2. Properties:
- Dry ice appears as a white, solid block or pellets.
- It is extremely cold, with a temperature of around -78.5 degrees Celsius (-109.3 degrees Fahrenheit).
- Unlike water ice, dry ice does not melt; it sublimates directly into carbon dioxide gas when exposed to higher temperatures.
3. Uses:
- Dry ice is commonly used as a cooling agent in various industries, such as food transportation, medical shipping, and scientific research.
- It is also utilized in fog machines for creating special effects in theatrical productions and concerts.
- Dry ice can be used for cleaning (known as dry ice blasting) to remove contaminants or to cool materials rapidly.
4. Safety Precautions:
- Dry ice should be handled with care since direct contact can cause frostbite or burns.
- It should never be stored in airtight containers as the sublimation of carbon dioxide gas can cause pressure buildup.
In conclusion, dry ice is the solid form of carbon dioxide and is widely used for its cooling properties in various industries. Its unique characteristics, such as sublimation and extreme coldness, make it a valuable resource for applications ranging from shipping to special effects.

Nail polish remover contains mainly:
- Acetone: The main ingredient in nail polish remover is acetone. Acetone is a colorless liquid that is highly effective in removing nail polish from nails. It is a powerful solvent that helps break down the polymers in the nail polish, making it easier to wipe away.
- Methanol: While some nail polish removers may contain small amounts of methanol, it is not the main ingredient. Methanol is a toxic alcohol that can be harmful if ingested or absorbed through the skin. It is not commonly used in nail polish removers due to its potential health risks.
- Ethanol: Ethanol, or ethyl alcohol, is another type of alcohol that may be present in nail polish removers. However, it is usually not the main ingredient. Ethanol is a solvent that can help dissolve the nail polish but is less effective than acetone.
- Limonene: Limonene is a natural solvent derived from citrus fruits. It is sometimes used in nail polish removers as an alternative to acetone or ethanol. However, it is not as commonly used as acetone or ethanol.
In summary, nail polish remover mainly contains acetone as the primary ingredient, with possible secondary ingredients such as ethanol or limonene. Methanol is generally not used due to its toxicity.

Explanation:
The question asks to identify the measurement that is not a unit of distance. Let's analyze each option:
A: Ammeter
- An ammeter is a device used to measure electric current and is not a unit of distance.
B: Cubit
- A cubit is an ancient unit of length, typically based on the length of a forearm, and is used to measure distances. It is a unit of distance.
C: Parsec
- A parsec is a unit of length used in astronomy to measure astronomical distances. It is equal to about 3.26 light-years and is a unit of distance.
D: Angstrom
- An angstrom is a unit of length equal to one ten-billionth of a meter and is commonly used to measure atomic and molecular distances. It is a unit of distance.
Therefore, the measurement that is not a unit of distance is A: Ammeter.

Discovery of X-rays

• Wilhelm Conrad Roentgen: The correct answer is B: Roentgen. He is credited with the discovery of X-rays.


• Background: In 1895, Wilhelm Conrad Roentgen, a German physicist, made the groundbreaking discovery of X-rays while conducting experiments with cathode rays.


• Experimental Setup: Roentgen was working with a cathode ray tube, which is a glass tube that contains a cathode and an anode. The tube is evacuated to create a vacuum.


• Observation: Roentgen noticed that a fluorescent screen placed near the tube started to glow even though it was not directly in the path of the cathode rays.


• Investigation: Further investigation revealed that the fluorescent glow was caused by a new type of ray that was being emitted from the cathode ray tube.


• Naming the New Rays: Roentgen initially referred to these new rays as "X-rays" since their nature was unknown. The term "X" represents an unknown variable in mathematics.


• Further Research: Roentgen conducted extensive research on X-rays and discovered their ability to pass through various materials, including human tissues, without causing harm.


• Impact: Roentgen's discovery of X-rays revolutionized the field of medicine, allowing for non-invasive imaging and diagnosis of internal structures.

Therefore, Wilhelm Conrad Roentgen is the scientist who discovered X-rays.

Acceleration is defined as the change in velocity over time. It is a fundamental concept in physics that describes how quickly an object's velocity changes.
Definition of Acceleration:
Acceleration is the rate at which an object's velocity changes over time. It is a vector quantity, meaning it has both magnitude and direction. The magnitude of acceleration is given by the formula:
Acceleration = (Change in Velocity) / (Change in Time)
Explanation:
Here is a detailed explanation of the concept of acceleration:
1. Change in Velocity:
Velocity is a vector quantity that represents the rate at which an object changes its position. It has both magnitude (speed) and direction. The change in velocity refers to the difference between the final velocity and the initial velocity of an object.
2. Change in Time:
Time is a scalar quantity that measures the duration of an event. The change in time refers to the difference between the final time and the initial time at which the change in velocity occurred.
3. Calculation of Acceleration:
Acceleration is calculated by dividing the change in velocity by the change in time. This formula gives the average acceleration over a specific time interval. Instantaneous acceleration, on the other hand, represents the acceleration at a specific moment in time.
4. Units of Acceleration:
The SI unit of acceleration is meters per second squared (m/s^2). It indicates how many meters per second the velocity of an object changes in one second.
5. Positive and Negative Acceleration:
Acceleration can be positive or negative, depending on the direction of the change in velocity. Positive acceleration occurs when an object's velocity increases, while negative acceleration (also known as deceleration or retardation) occurs when the velocity decreases.
Example:
To illustrate the concept of acceleration, consider the following example:
Suppose a car is initially at rest and then accelerates uniformly to a velocity of 30 m/s in 5 seconds. The change in velocity is (30 m/s - 0 m/s) = 30 m/s, and the change in time is 5 seconds. Using the formula for acceleration, we can calculate:
Acceleration = (Change in Velocity) / (Change in Time)
Acceleration = 30 m/s / 5 s
Acceleration = 6 m/s^2
Thus, the car's acceleration is 6 m/s^2 in the positive direction.
In conclusion, acceleration is defined as the change in velocity over time. It is a crucial concept in physics and helps describe how objects move and change their velocity.

Which one of the following is caused by a virus?

• Cholera: Cholera is caused by the bacterium Vibrio cholerae and is typically transmitted through contaminated food or water. It is not caused by a virus.


• Influenza: Influenza, also known as the flu, is caused by the influenza virus. It is a highly contagious respiratory illness that spreads through respiratory droplets when an infected person coughs, sneezes, or talks.


• Scabies: Scabies is a skin infestation caused by the microscopic mite Sarcoptes scabiei. It is not caused by a virus.


• Typhoid: Typhoid fever is caused by the bacterium Salmonella typhi and is primarily transmitted through contaminated food or water. It is not caused by a virus.

Therefore, the correct answer is Influenza (B), which is caused by a virus.

Element required for the hardening of Bones and teeth:
The element required by the human body for the hardening of bones and teeth is Phosphorus.
Explanation:
- Phosphorus is an essential mineral that plays a crucial role in the formation and maintenance of strong bones and teeth.
- It is one of the key components of hydroxyapatite, which is the mineralized matrix that gives bones and teeth their hardness and strength.
- Phosphorus works in conjunction with calcium to form calcium phosphate, which is the main mineral present in bones and teeth.
- It helps in the growth, development, and repair of bones and teeth, and also aids in the absorption and utilization of other minerals like calcium and magnesium.
- A deficiency of phosphorus can lead to weakened bones, tooth decay, and other skeletal issues.
- Good sources of phosphorus include dairy products, meat, fish, poultry, nuts, legumes, and whole grains.
Therefore, the correct answer is C: Phosphorus.

Which one of the following is not caused by Nutritional deficiency?
The correct answer is B: Haemophilia.
Explanation:
Haemophilia is a genetic disorder caused by a deficiency in clotting factors in the blood, not by nutritional deficiency. It is inherited and primarily affects males.
The other options mentioned, A, C, and D, are all nutritional deficiencies that can occur due to inadequate intake of specific nutrients.
Let's discuss each option in detail:
A: Kwashiorkor
- Kwashiorkor is a form of severe protein-energy malnutrition.
- It is caused by a lack of protein in the diet.
- It commonly occurs in children in developing countries who rely heavily on starchy foods with little protein.
B: Haemophilia
- Haemophilia is a genetic disorder that affects the blood's ability to clot.
- It is caused by a deficiency in clotting factors, specifically factor VIII (hemophilia A) or factor IX (hemophilia B).
- This disorder is not related to nutritional deficiencies.
C: Beriberi
- Beriberi is a disease caused by a deficiency of thiamine (vitamin B1) in the diet.
- It can result from a diet consisting mainly of polished rice or other refined grains.
- Symptoms can include weakness, loss of appetite, nerve damage, and heart problems.
D: Marasmus
- Marasmus is a severe form of malnutrition caused by a lack of calories and protein.
- It primarily affects young children in impoverished areas.
- Symptoms include severe wasting, muscle atrophy, and stunted growth.
In summary, while Kwashiorkor, Beriberi, and Marasmus are all caused by nutritional deficiencies, Haemophilia is a genetic disorder unrelated to nutritional intake.

Chemically, what is Sname Venom?
Answer: C. Protein
Explanation:
Sname venom is chemically composed of proteins. Here are the details:
1. Definition of Venom:
Venom is a toxic substance produced by certain animals such as snakes, spiders, and scorpions. It is used to immobilize or kill prey, defend against predators, or for other purposes.
2. Composition of Venom:
Venom is a complex mixture of various substances, including proteins, enzymes, peptides, and other bioactive molecules. These components work together to produce the venom's toxic effects.
3. Protein Content in Venom:
Proteins are the main component of snake venom. They are responsible for the venom's toxic properties. Different snake species produce different types and amounts of proteins in their venom.
4. Function of Venom Proteins:
Venom proteins have various biological functions, including:
- Neurotoxicity: Some venom proteins target the nervous system, causing paralysis or disrupting neural signals.
- Hemotoxicity: Other venom proteins affect the blood, leading to coagulation disorders or tissue damage.
- Cytotoxicity: Certain venom proteins can damage cells and tissues directly.
- Enzymatic Activity: Many venom proteins are enzymes that modify or degrade specific molecules in the victim's body.
5. Importance of Venom Proteins:
Venom proteins are of great interest in scientific research and medical applications. They have been used to develop antivenom treatments, study molecular interactions, and explore potential therapeutic uses.
In conclusion, snake venom is primarily composed of proteins, which play a crucial role in its toxic effects on prey or potential threats.

The root of which one of the following plants contain the bacteria that convert free Nitrogen to Nitrates used by plants?
The correct answer is B: Pea.
Explanation:
The process of converting free nitrogen gas into nitrates that can be used by plants is called nitrogen fixation. This process is performed by certain bacteria, known as nitrogen-fixing bacteria, which form a symbiotic relationship with plant roots.
Here is a detailed explanation of why the root of a pea plant contains the bacteria that convert free nitrogen to nitrates:
1. Nitrogen fixation: Nitrogen fixation is the process by which atmospheric nitrogen (N2) is converted into a usable form, such as nitrates (NO3-), by nitrogen-fixing bacteria.
2. Nitrogen-fixing bacteria: There are specific bacteria, such as Rhizobium, that have the ability to fix atmospheric nitrogen. These bacteria form a symbiotic relationship with the roots of certain plants, including peas.
3. Symbiotic relationship: Pea plants have specialized structures on their roots called nodules. These nodules contain the nitrogen-fixing bacteria. The bacteria live inside the nodules and receive carbohydrates and other nutrients from the plant. In return, the bacteria convert atmospheric nitrogen into a usable form for the plant.
4. Pea plant: Pea plants belong to a group of plants called legumes. Legumes have a unique ability to form symbiotic relationships with nitrogen-fixing bacteria. The bacteria colonize the roots of legumes and provide them with a source of nitrogen. This allows legumes, including peas, to grow well in nitrogen-deficient soils.
5. Role of nitrates: Nitrates are an essential nutrient for plant growth and development. They are a major component of proteins and other important molecules in plants. By converting atmospheric nitrogen into nitrates, the bacteria in the root nodules of pea plants provide a vital source of nitrogen for the plant's growth.
In conclusion, the root of a pea plant contains the bacteria that convert free nitrogen to nitrates used by plants. This symbiotic relationship between the pea plant and the nitrogen-fixing bacteria allows the plant to access a valuable source of nitrogen for its growth and development.

Which one among the following is rich in protein?
Answer: D. Fried Gram
Explanation:
Fried Gram, also known as roasted chana or dalia, is rich in protein compared to the other options given. Let's break down each option and analyze their protein content:
A. Boiled rice:
- Rice is a staple food, but it is not particularly high in protein.
- Boiled rice contains around 2-3 grams of protein per 100 grams.
B. Bread of Wheat:
- Wheat bread is a good source of carbohydrates and fiber but is not as high in protein.
- On average, wheat bread contains around 7-10 grams of protein per 100 grams.
C. Fried Potato Chips:
- Potato chips are primarily made from potatoes, which are high in carbohydrates but low in protein.
- Fried potato chips generally contain less than 2 grams of protein per 100 grams.
D. Fried Gram:
- Fried gram, also known as roasted chana or dalia, is a legume that is rich in protein.
- It is an excellent source of plant-based protein and provides around 20-25 grams of protein per 100 grams.
In summary, among the given options, fried gram (roasted chana or dalia) is the best choice as it is rich in protein compared to boiled rice, bread of wheat, and fried potato chips.

The part of the potato plant used as a vegetable is the modified stem.
Explanation:
The potato plant, scientifically known as Solanum tuberosum, is a flowering plant that belongs to the nightshade family. The part of the plant that is commonly consumed as a vegetable is the tuber, which is the modified stem of the plant.
Here is a detailed explanation of why the modified stem of the potato plant is used as a vegetable:
- Tubers: The tuber is an underground stem structure that stores nutrients for the plant. It is swollen and enlarged, containing starches, sugars, and other nutrients that support the growth of the plant. These tubers are what we commonly refer to as potatoes.
- Edible: The tubers of the potato plant are edible and have been cultivated as a staple food in many cultures for centuries. They can be harvested and cooked in various ways, including boiling, baking, frying, and mashing.
- Nutritional Value: Potatoes are a good source of carbohydrates, dietary fiber, vitamin C, potassium, and other essential nutrients. They provide energy, help maintain proper digestion, support immune function, and contribute to overall health and well-being.
- Culinary Uses: Potatoes are incredibly versatile and can be used in a wide range of culinary preparations. They can be used as a main ingredient in dishes like mashed potatoes, French fries, potato salad, and soups. They can also be used as a thickening agent in stews and gravies.
- Storage: The tubers of the potato plant have a relatively long shelf life and can be stored for extended periods under suitable conditions. This makes them a convenient and readily available vegetable option for consumption.
In conclusion, the modified stem of the potato plant, known as the tuber, is the part that is used as a vegetable. It offers nutritional value, culinary versatility, and storage benefits, making it a popular and widely consumed food worldwide.

What are mushrooms?
- Mushrooms are multicellular organisms that belong to the kingdom Fungi.
Why are mushrooms classified as fungi?
- Fungi are a separate kingdom of organisms that are distinct from plants, animals, and algae.
- Mushrooms share several characteristics with other fungi, such as:
- Lack of chlorophyll and inability to perform photosynthesis.
- Presence of chitin in their cell walls.
- Reproduction through spore production.
- Dependence on organic matter for nutrition.

Distinguishing mushrooms from other options:
- Algae:
- Algae are photosynthetic organisms that can be found in water or damp environments.
- Algae are not multicellular like mushrooms.
- Lichens:
- Lichens are symbiotic associations between fungi and algae or cyanobacteria.
- While mushrooms are fungi, they can form lichens in some cases.
- Parasitic moss plant:
- Mosses are small, non-vascular plants that belong to the division Bryophyta.
- Mushrooms are not parasitic moss plants; they are fungi that obtain nutrients from decaying organic matter.

Conclusion:
- Mushrooms are classified as fungi due to their unique characteristics, such as lack of chlorophyll, presence of chitin in their cell walls, and dependence on organic matter for nutrition.

Enzymes: The Nature and Composition
Introduction:
Enzymes are biological catalysts that speed up chemical reactions in living organisms. They play a crucial role in various metabolic processes and are essential for maintaining cellular functions.
Composition:
Enzymes are composed of proteins, which are made up of amino acids. These amino acids are linked together in a specific sequence to form a polypeptide chain, which then folds into a specific three-dimensional structure.
Key Points:
- Enzymes are actually proteins and not carbohydrates, fatty acids, or sterols.
- Proteins are organic macromolecules composed of amino acids.
- Enzymes exhibit a high degree of specificity, meaning they catalyze specific reactions.
- The catalytic activity of enzymes is determined by their unique three-dimensional structure.
- Enzymes can be denatured or rendered non-functional by extreme pH, temperature, or chemicals.
- Enzymes are involved in various biological processes such as digestion, metabolism, and DNA replication.
- Enzymes can be classified into different types based on the type of reaction they catalyze.
- Enzymes are often named based on the substrate they act upon and the type of reaction they catalyze.
Conclusion:
In summary, enzymes are proteins that act as biological catalysts in living organisms. Their composition, specifically their amino acid sequence and three-dimensional structure, allows them to exhibit their catalytic activity. Understanding the nature and composition of enzymes is crucial in studying their role in various biological processes.

Explanation:
True fruits:
- True fruits are formed from the ovary of a flower after fertilization.
- They contain seeds.
- Examples of true fruits include apples, dates, and coconuts.
Not a true fruit:
- A tomato is not a true fruit.
- It is classified as a berry or a false fruit.
- The edible part of a tomato is derived from the ovary and other parts of the flower.
- However, it does not contain seeds, as they are located in the gel-like substance surrounding the seeds.
- Therefore, a tomato is considered a false fruit or a vegetable in culinary terms.
Conclusion:
- Among the given options, the fruit that is not a true fruit is the tomato.
- The other options, such as apple, coconut, and date, are all true fruits as they are formed from the ovary of a flower and contain seeds.

Answer:
Organ: Liver
Explanation:
Ammonia is a toxic waste product that is produced during protein metabolism in the body. It is important to convert ammonia into a less toxic compound before it can be safely eliminated from the body. This conversion takes place in the liver.
Process:
1. Urea Cycle: The liver contains enzymes that are involved in a series of chemical reactions known as the urea cycle. This cycle converts ammonia into urea, a much less toxic compound.
2. Ammonia Conversion: In the urea cycle, ammonia combines with carbon dioxide to form urea. This reaction occurs in several steps involving different enzymes, such as ornithine transcarbamylase, argininosuccinate synthetase, and argininosuccinate lyase.
3. Urea Transport: Once urea is formed, it is transported from the liver to the kidneys through the bloodstream. In the kidneys, urea is filtered out of the blood and excreted in the urine.
4. Kidney's Role: While the kidney plays a crucial role in excreting urea, it is important to note that the conversion of ammonia into urea primarily occurs in the liver.
In summary, the liver is responsible for converting ammonia into urea through the urea cycle. This process enables the body to safely eliminate ammonia as urea, preventing its toxic buildup in the bloodstream.

Who saw the cells for the first time in the thin slice of Cork using his crude Micro-scope?
The correct answer is D: Robert Hooke.
Explanation:
- Robert Hooke was an English scientist who is known for his contributions to biology and microscopy.
- In 1665, Hooke examined a thin slice of cork under his crude microscope and observed a series of empty spaces resembling small rooms or cells.
- He called these structures "cells" for their resemblance to the cells of a monastery.
- Hooke's discovery of cells in cork was significant because it was the first time that the existence of cells was observed and documented.
- This discovery laid the foundation for the cell theory, which states that all living organisms are composed of cells.
- Hooke's observations and drawings of cells were published in his book "Micrographia," which became a landmark in microscopy and biology.
In conclusion, Robert Hooke saw the cells for the first time in the thin slice of Cork using his crude microscope. His discovery of cells in cork was a significant contribution to the field of biology and laid the foundation for the cell theory.

Founder of Facebook:
Mark Zuckerberg is the founder of the company Facebook.
Explanation:
- Mark Zuckerberg, born on May 14, 1984, is an American entrepreneur and computer programmer.
- He co-founded Facebook in 2004 while studying at Harvard University.
- Together with his college roommates, Eduardo Saverin, Andrew McCollum, Dustin Moskovitz, and Chris Hughes, Zuckerberg launched Facebook as a social networking platform initially limited to Harvard students.
- The platform quickly expanded to other universities and then to the general public, becoming one of the largest social media platforms in the world.
- Mark Zuckerberg has served as the CEO and chairman of Facebook since its inception.
- Under his leadership, Facebook has grown to have billions of active users and has acquired several other companies, including Instagram and WhatsApp.
- Zuckerberg is known for his innovative approach to connecting people and his vision of creating a more open and connected world through technology.
- He has faced both praise and criticism for his role in shaping the social media landscape and handling user data privacy concerns.
In summary, Mark Zuckerberg is the founder of Facebook, having started the company while studying at Harvard University. He has since led the company as its CEO and chairman, making it one of the most influential and widely used social media platforms in the world.

When is National Youth Day celebrated?
National Youth Day is celebrated on January 12th.
Detailed
The celebration of National Youth Day on January 12th is to commemorate the birth anniversary of Swami Vivekananda, a renowned spiritual leader and philosopher. Here is a detailed explanation of the significance and celebration of National Youth Day:

• Birth Anniversary of Swami Vivekananda: National Youth Day is celebrated on January 12th, as it marks the birth anniversary of Swami Vivekananda. He was born on January 12, 1863, in Kolkata, India.


• Inspiring the Youth: Swami Vivekananda was a great source of inspiration for the youth. He played a crucial role in the revival of Hindu philosophy, promoting education, spirituality, and national integration.


• Recognition of Youth Power: National Youth Day is observed to recognize the potential and power of the youth in shaping the future of the nation. It aims to empower the youth and encourage them to contribute positively to society.


• Seminars and Workshops: On National Youth Day, various educational institutions, youth organizations, and government bodies organize seminars, workshops, and cultural events. These events focus on topics such as leadership, personality development, career guidance, and social awareness.


• Importance of Education: Swami Vivekananda emphasized the importance of education in the holistic development of individuals. Therefore, on National Youth Day, educational institutions highlight the significance of education and its role in shaping the youth.


• Volunteering and Social Service: National Youth Day also promotes the spirit of volunteering and social service among the youth. Many organizations encourage young people to engage in activities that benefit society and make a positive impact.


• Inspiring Quotes and Teachings: Swami Vivekananda's teachings and quotes are shared widely on National Youth Day. His thoughts on self-confidence, spirituality, and the power of the youth serve as a guiding light for the younger generation.

In conclusion, National Youth Day is celebrated on January 12th to honor the birth anniversary of Swami Vivekananda and inspire the youth to become responsible, empowered, and compassionate individuals who contribute positively to society.