All Free Biology MCQs with Answers

• A. 50
• B. 80
• C. 85
• D. 90

Explanation: 85 percent of brain cells consist of water. Water is essential for the brain's proper functioning, providing a medium for biochemical reactions, aiding in the transport of nutrients and waste, and helping maintain cellular structure and electrical activity. Its high content ensures that neurons and glial cells can perform their complex signaling and metabolic tasks efficiently. Consequently, the brain's water content is crucial for cognition, coordination, and overall neurological health.

• A. Phospholipid
• B. Polysaccharides
• C. Protein
• D. Both B and C

Explanation: Glycogen is a polysaccharide (carbohydrate) found in muscles and liver. Glycogen belongs to a group of polysaccharide carbohydrates.

• A. 0.008
• B. 0.0008
• C. 0.018
• D. 0.08

Explanation: In human blood, glucose is typically found at a concentration of about 0.08%. This is the standard level needed for maintaining normal bodily functions, such as providing energy to cells. Option A (0.008%) and Option B (0.0008%) suggest concentrations far lower than the norm, which are not sufficient for normal physiological processes. Option C (0.018%) is closer but still below the typical range. Therefore, the correct answer is Option D, 0.08%, which accurately reflects the normal glucose concentration in blood.

• A. Polysaccharides
• B. Monosaccharides
• C. Oligosaccharides
• D. Sucrose

Explanation: Monosaccharides are the simplest form of carbohydrates and are often referred to as simple sugars. They are the building blocks of more complex carbohydrates like disaccharides and polysaccharides. Monosaccharides are composed of carbon, hydrogen, and oxygen atoms in a ratio of 1:2:1, and they serve as a primary source of energy for living organisms. The most common monosaccharides include glucose, fructose, and galactose.

• A. Cellulose
• B. Agar
• C. Glycogen
• D. Chitin

Explanation: Glycogen is the correct answer as it is the form of energy storage polysaccharide in animals, similar to starch in plants. It is a highly branched polymer of glucose. Cellulose, agar, and chitin serve different roles: cellulose provides structural support in plants, agar is used for its gelatinous properties, and chitin forms structural components in arthropods and fungi. None of these are used for energy storage in animals.

• A. Fructose
• B. Glucose
• C. Sucrose
• D. All are monosaccharides

Explanation: The correct answer is Sucrose. Sucrose is a disaccharide, meaning it consists of two monosaccharide units: glucose and fructose. This distinguishes it from fructose and glucose, which are monosaccharides, or single sugar units. Option D is incorrect because not all listed options are monosaccharides; sucrose is a disaccharide.

• A. Sugar cane
• B. Milk
• C. Almonds
• D. None of these

Explanation: Sucrose is a disaccharide composed of glucose and fructose, commonly found in sugar cane and sugar beet. Sugar cane is cultivated extensively for its sap, which is processed to extract sucrose, making it a primary source of table sugar. Milk, on the other hand, contains lactose, not sucrose, as its main sugar. Almonds do not naturally contain sucrose; they are a source of proteins, healthy fats, and other nutrients. Therefore, the correct answer is sugar cane, as it is directly associated with sucrose production.

• A. Green vegetables
• B. Grapes
• C. Rice
• D. All of these

Explanation: Green vegetables are valuable for diabetic control because they are low in carbohydrates and high in dietary fiber, which helps stabilize blood sugar levels. On the other hand, grapes are high in natural sugars, and rice is high in carbohydrates, both of which can lead to increased blood sugar levels. Therefore, while grapes and rice have nutritional benefits, they are not as suitable for diabetic control as green vegetables.

• A. Liver
• B. Muscles
• C. Kidneys
• D. Both A and B

Explanation: The correct answer is that glycogen is most abundantly present in both the liver and muscles. The liver stores glycogen to help regulate blood glucose levels and provide energy between meals, while muscles store glycogen for use during physical activity. The kidneys, on the other hand, do not store glycogen; their primary role is in filtering blood and producing urine, making option C incorrect.

• A. Starch
• B. Glycogen
• C. Amylose
• D. Amylopectin

Explanation: The correct answer is amylose, as it is the only option that is soluble in hot water. Amylose consists of a linear chain of glucose units connected by α-1,4-glycosidic bonds, allowing it to dissolve by forming hydrogen bonds with water. In contrast, amylopectin and glycogen are highly branched, making them too large and complex to dissolve in hot water. Starch, composed of both amylose and amylopectin, is not completely soluble due to the higher proportion of insoluble amylopectin.