Life Processes - Practice Test, Class 10 Science MCQs & solutions Free

Villi is present in small intestine which is finger-like projection. And they also help in increasing area for absorption.

Metal Associated with Hemoglobin: Iron
Explanation:
Hemoglobin is a protein found in red blood cells that is responsible for carrying oxygen from the lungs to various tissues and organs in the body. It is an essential component of the circulatory system.
The metal associated with hemoglobin is iron. Iron is a crucial element in the structure and function of hemoglobin. It is responsible for binding with oxygen molecules and carrying them throughout the body.
Here are some key points to support this answer:
- Hemoglobin consists of four protein subunits, each containing a heme group.
- The heme group contains an iron atom, which is essential for the binding of oxygen.
- When oxygen molecules come into contact with the iron atom in the heme group, they form a reversible bond.
- This reversible binding and release of oxygen enable hemoglobin to transport oxygen molecules to tissues and organs.
- Iron also plays a role in the synthesis and production of new red blood cells.
In summary, iron is the metal associated with hemoglobin, and its presence is vital for the proper functioning of the circulatory system and oxygen transport in the body.

The process of digestion of food starts in the mouth.
- The mouth is the first organ involved in the process of digestion.
- It contains several structures that aid in the breakdown of food.
- The teeth are responsible for chewing and breaking down food into smaller pieces, increasing the surface area for digestion.
- The tongue helps in manipulating the food and mixing it with saliva.
- Saliva, produced by the salivary glands, contains enzymes that begin the digestion of carbohydrates.
- These enzymes, such as amylase, break down complex carbohydrates into simpler sugars.
- The food is then formed into a ball called a bolus and is swallowed, entering the food canal or the esophagus.
- From the esophagus, the bolus moves down into the stomach.
- In the stomach, the process of digestion continues with the release of gastric juices.
- These juices contain enzymes and acids that break down proteins and kill bacteria present in the food.
- The partially digested food, now called chyme, moves into the small intestine for further digestion and absorption of nutrients.
In conclusion, the process of digestion starts in the mouth where food is broken down into smaller pieces and mixed with saliva containing enzymes. Therefore, the correct answer is C: Mouth.

Function of the Kidneys:
The kidneys in human beings are responsible for the process of excretion. Excretion is the removal of waste products from the body. The kidneys perform several important functions to maintain the body's internal environment.
Key Functions of the Kidneys:
1. Filtration: The kidneys filter the blood to remove waste products, excess water, and toxins. They help maintain the balance of electrolytes, such as sodium, potassium, and calcium, in the body.
2. Regulation of Fluid Balance: The kidneys regulate the amount of water in the body by adjusting the volume of urine produced. They help maintain proper hydration levels and prevent dehydration.
3. Regulation of Blood Pressure: The kidneys play a crucial role in regulating blood pressure. They produce a hormone called renin, which helps control blood pressure by influencing the constriction and dilation of blood vessels.
4. Acid-Base Balance: The kidneys help maintain the acid-base balance in the body by excreting hydrogen ions and reabsorbing bicarbonate ions. This helps regulate the pH of the blood.
5. Production of Hormones: The kidneys produce hormones such as erythropoietin, which stimulates the production of red blood cells, and calcitriol, which helps regulate calcium and phosphate levels in the body.
6. Detoxification: The kidneys aid in the detoxification process by filtering and eliminating waste products, drugs, and toxins from the body.
7. Metabolism of Vitamins: The kidneys are involved in the metabolism of vitamin D, converting it into its active form (calcitriol), which is essential for calcium absorption and bone health.
Conclusion:
The kidneys are an essential part of the excretory system in human beings. They perform multiple functions to maintain the body's internal environment, including filtration, regulation of fluid balance, blood pressure regulation, acid-base balance, hormone production, detoxification, and metabolism of vitamins.

Liver secretes bile in the human digestive system.
Bile is an important digestive fluid that plays a crucial role in the digestion and absorption of fats. It is produced by the liver and stored in the gallbladder. When food enters the small intestine, bile is released into the duodenum, the first part of the small intestine, through the common bile duct.
Explanation:
Here is a detailed explanation of why bile is secreted by the liver in the human digestive system:
1. Function of bile: Bile helps in the digestion and absorption of fats. It emulsifies fats, breaking them down into smaller droplets, which increases the surface area for the action of digestive enzymes. This process allows for the efficient digestion and absorption of fats in the small intestine.
2. Liver production: Bile is produced by the liver cells, specifically by the hepatocytes. The liver continuously produces bile, which is then transported to the gallbladder for storage.
3. Bile composition: Bile is composed of bile salts, bile pigments (such as bilirubin), cholesterol, phospholipids, and electrolytes. These components work together to facilitate fat digestion.
4. Gallbladder storage: After production, bile is transported from the liver to the gallbladder through the bile ducts. The gallbladder acts as a storage organ for bile. When needed for digestion, the gallbladder contracts, releasing bile into the small intestine.
5. Bile release: When fatty food enters the small intestine, the hormone cholecystokinin (CCK) is released. CCK stimulates the gallbladder to contract, causing the release of bile into the duodenum through the common bile duct.
6. Bile's role in digestion: Once in the small intestine, bile emulsifies fats, breaking them down into smaller droplets. This process, aided by pancreatic lipase (an enzyme produced by the pancreas), allows for the efficient digestion of fats into fatty acids and glycerol.
In summary, bile is secreted by the liver in the human digestive system. It plays a crucial role in the digestion and absorption of fats by emulsifying them and increasing their digestibility.

The Action of Bile
The action of bile can be termed as emulsification. Bile is a substance produced by the liver and stored in the gallbladder. It plays a crucial role in the digestion and absorption of fats. Here's how bile functions in the process of emulsification:
1. Definition:
- Emulsification is the process of breaking down large fat globules into smaller droplets, increasing their surface area.
2. Composition of Bile:
- Bile contains bile salts, which are amphipathic molecules. This means that they have both hydrophilic (water-loving) and hydrophobic (fat-loving) properties.
- Other components of bile include bile pigments, cholesterol, phospholipids, and electrolytes.
3. Function of Bile in Emulsification:
- Bile salts in bile interact with fat molecules, forming micelles.
- Micelles are tiny aggregates where the hydrophobic ends of bile salts surround the fat molecules, while the hydrophilic ends face outward, interacting with the watery environment.
- This arrangement of bile salts helps to disperse and suspend fat droplets in the watery environment of the digestive system, preventing them from clumping together.
4. Importance of Emulsification:
- Emulsification increases the surface area of fat droplets, which enables the action of pancreatic enzymes called lipases.
- Lipases break down the smaller fat droplets into fatty acids and glycerol, which can be easily absorbed by the intestinal lining.
5. Role of Bile in Absorption:
- Bile also aids in the absorption of fat-soluble vitamins (A, D, E, and K) and certain dietary compounds, such as cholesterol.
- It helps in the transport of these substances across the intestinal membrane.
In summary, the action of bile can be described as emulsification, which involves the breakdown of large fat globules into smaller droplets, increasing their surface area for efficient digestion and absorption.

To determine which organism can live without oxygen or air, let's analyze each option:
Option A: Amoeba
- Amoeba is a microscopic single-celled organism.
- It is capable of living in various environments, including freshwater and soil.
- Amoeba obtains energy through the process of phagocytosis, where it engulfs and consumes other small organisms.
- While amoeba can survive in low oxygen environments, it still requires some level of oxygen to survive.
Option B: Sheep
- Sheep are mammals that require oxygen to survive.
- Like all mammals, sheep have lungs that facilitate the exchange of oxygen and carbon dioxide.
- They rely on oxygen from the air to carry out cellular respiration and produce energy.
Option C: Yeast
- Yeast is a single-celled fungus that can perform both aerobic and anaerobic respiration.
- In the presence of oxygen, yeast undergoes aerobic respiration, producing energy more efficiently.
- However, yeast can also switch to anaerobic respiration when oxygen is not available.
- During anaerobic respiration, yeast ferments sugars, converting them into alcohol and carbon dioxide.
- This ability allows yeast to survive in environments with low or no oxygen.
Option D: Leech
- Leeches are a type of segmented worm that are primarily aquatic.
- While they can tolerate low oxygen levels, leeches still require oxygen to survive.
- Leeches have a specialized respiratory system that allows them to extract oxygen from water.
- They have two suckers, one at each end of their body, which they use to attach to surfaces and obtain oxygen.
Therefore, based on the given options, the organism that can live without oxygen or air is Yeast (Option C).

Respiration is a process in which:
- Energy is released: Respiration is an essential metabolic process that occurs in living organisms, including plants and animals. During respiration, energy is released from organic molecules, such as glucose, through a series of chemical reactions.
- Stored in the form of ATP: The released energy is stored in the form of adenosine triphosphate (ATP), which is the primary energy currency of cells. ATP is a high-energy molecule that can be used by cells to perform various functions, such as muscle contraction, active transport, and synthesis of macromolecules.
- ATP: ATP is formed through a process called oxidative phosphorylation in the mitochondria of cells. During this process, the energy released from the breakdown of glucose is used to generate ATP molecules.
- ADP: The energy released during respiration is not stored in the form of ADP (adenosine diphosphate), as mentioned in option A. ADP is converted back into ATP through the addition of a phosphate group during cellular respiration.
- Energy is used up: Option B states that energy is used up during respiration, which is not accurate. Respiration is a process that releases energy rather than consuming it.
Therefore, the correct answer is C: Energy is released and stored in the form of ATP during respiration.

Introduction:
The transportation of oxygenated blood from the lungs to the left auricle is an essential process in the circulatory system. This process ensures that oxygen-rich blood is supplied to the body's tissues and organs.
Answer:
The correct answer is B: pulmonary vein. The oxygenated blood is carried from the lungs to the left auricle by the pulmonary veins.
Explanation:
The process of carrying oxygenated blood from the lungs to the left auricle involves the following steps:
1. Oxygenation in the Lungs:
- Deoxygenated blood from the body enters the lungs through the pulmonary artery.
- In the lungs, the blood is oxygenated as it passes through the tiny capillaries surrounding the alveoli.
- Oxygen molecules diffuse from the alveoli into the blood, while carbon dioxide diffuses from the blood into the alveoli.
2. Pulmonary Veins:
- Once the blood is oxygenated, it is collected by the pulmonary veins.
- The pulmonary veins are a network of blood vessels that carry oxygenated blood back to the heart.
- Unlike other veins in the body that carry deoxygenated blood, the pulmonary veins specifically transport oxygenated blood.
3. Left Auricle:
- The oxygenated blood is transported from the pulmonary veins to the left auricle of the heart.
- The left auricle is one of the four chambers of the heart, located on the left side.
- It receives the oxygenated blood and then contracts to pump it into the left ventricle.
4. Further Circulation:
- From the left ventricle, the oxygenated blood is pumped out into the aorta, the largest artery in the body.
- The aorta then distributes the oxygenated blood to the various arteries, which further carry it to different parts of the body for oxygen supply.
In summary, the pulmonary veins are responsible for carrying oxygenated blood from the lungs to the left auricle of the heart, ensuring that the body's tissues receive a fresh supply of oxygen.

Explanation:
When air is blown from the mouth into a test tube containing lime water, the lime water turns milky. This is due to the presence of carbon dioxide gas.
Reasoning:
Here is the detailed explanation of why lime water turns milky when air is blown into it:
1. Lime water, or calcium hydroxide solution, is a clear and colorless liquid.
2. Calcium hydroxide reacts with carbon dioxide gas to form calcium carbonate, which is insoluble and appears as a white precipitate.
3. The reaction can be represented by the following equation: Ca(OH)2 + CO2 → CaCO3 + H2O
4. When air is blown into the lime water, it contains a small amount of carbon dioxide gas.
5. The carbon dioxide gas present in the exhaled breath reacts with the calcium hydroxide in the lime water.
6. This reaction produces calcium carbonate, which precipitates and causes the lime water to become milky or cloudy in appearance.
7. The milky appearance is due to the formation of numerous tiny calcium carbonate particles suspended in the liquid.
Conclusion:
When air is blown into a test tube containing lime water, the lime water turns milky due to the presence of carbon dioxide gas.

Amoeba captures food with the help of pseudopodia.
The process of capturing food in amoeba involves the following steps:
1. Extension of pseudopodia: Amoeba extends its pseudopodia, which are temporary projections of its cell membrane and cytoplasm.
2. Movement towards the food: The pseudopodia help in amoeba's movement towards the food source.
3. Enclosure of food: As the amoeba reaches the food, pseudopodia surround the food particles, forming a temporary food vacuole.
4. Engulfment: The pseudopodia then engulf the food particles along with a small amount of surrounding water, enclosing them within the food vacuole.
5. Formation of a food vacuole: The food vacuole is formed by the fusion of pseudopodia. It contains the food particles and water.
6. Digestion: Enzymes present in the food vacuole begin to break down the food particles into simpler substances, allowing for the absorption of nutrients.
7. Excretion: Once digestion is complete, undigested waste material is eliminated from the amoeba through the process of exocytosis.
Overall, the pseudopodia of amoeba play a crucial role in capturing and engulfing food particles, allowing for their digestion and absorption.