All Free Biology MCQs with Answers

• A. Polarity
• B. Universal solvent
• C. High specific heat and High heat of vaporization
• D. Polarity, Universal solvent, High specific heat and High heat of vaporization

Explanation: Water is biologically important due to its unique properties. The correct answer is Polarity, Universal solvent, High specific heat and High heat of vaporization. Water's polarity allows it to form hydrogen bonds, making it a universal solvent capable of dissolving various substances, which is vital for biochemical reactions. Its high specific heat and heat of vaporization help stabilize temperatures within organisms, contributing to homeostasis. Options A, B, and C highlight individual properties, but only Option D includes the full range of water's attributes that underscore its essential role in biological systems.

• A. 20%
• B. 10%
• C. 70%
• D. 50%

Explanation: Water is vital for the survival of cells as it facilitates biochemical reactions, aids in transportation within the cell, and helps maintain structural integrity. Most living cells have a water content of approximately 70% to 90%. This range allows cells to function effectively and maintain homeostasis. Option C, with 70% water content, is correct because it falls within this optimal range. Options A and B, with 20% and 10% respectively, are too low and would result in cellular damage. Option D, at 50%, while closer, is still generally insufficient for most cells to maintain their vital functions.

• A. Hydrolysis
• B. Condensation
• C. Hydrogenation
• D. Decarboxylation

Explanation: The correct answer is Condensation. In condensation reactions, smaller molecules combine to form larger organic molecules, and a water molecule is removed in the process, which aligns perfectly with the question's description. Hydrolysis does the opposite by breaking down molecules with water. Hydrogenation and decarboxylation are unrelated to water removal in synthesis processes.

• A. Hydrophobic properties
• B. Hydrophilic properties
• C. Very good solvent
• D. Strong surface tension

Explanation: Hydrophobic properties refer to the tendency of certain substances to repel or not mix well with water. Hydrophobic substances are typically non-polar and do not readily dissolve in water. Instead, they tend to clump together or form separate phases. This property is often observed in substances like oils, fats, and waxes but not in water. Therefore, the correct statement for a property that is not associated with water is "A".

• A. Insoluble in hot water
• B. Sparingly soluble in hot water
• C. Sparingly soluble in cold water
• D. Highly soluble in hot water

Explanation: Polysaccharides, composed of long chains of monosaccharide units, exhibit limited solubility in hot water due to their complex molecular structure. While monosaccharides and disaccharides dissolve more readily, polysaccharides only dissolve to a limited extent in hot water, making Option B correct. Options A and D incorrectly suggest they are either insoluble or highly soluble in hot water. Option C is incorrect because polysaccharides have even lower solubility in cold water.

• A. Liver
• B. Spleen
• C. White Blood Cells (W.B.C.)
• D. Skin cells

Explanation: The correct answer is the liver. The liver is responsible for storing glycogen, which is a form of glucose storage. It releases glucose into the bloodstream when needed to maintain blood glucose levels. The spleen, while part of the immune system, does not store glycogen. White blood cells are involved in immune response and do not function in glycogen storage. Skin cells serve as a protective barrier and also do not store glycogen.

• A. 0.8%
• B. 0.08%
• C. 0.06%
• D. 6%

Explanation: The correct answer is 0.08%. Blood plasma typically contains about 0.08% glucose, which is crucial for providing energy to cells. Option A (0.8%) and Option D (6%) are much higher than physiological levels and could indicate a serious health issue if true. Option C (0.06%) is close to the correct value, but slightly lower than the typical concentration in blood.

• A. Cellulose
• B. Glycogen
• C. Wax
• D. Protein

Explanation: Cotton is composed almost entirely of cellulose, a complex carbohydrate that forms the structural component of plant cell walls. Cellulose is a linear polymer of glucose molecules connected by β-1,4 glycosidic bonds, which provides rigidity and strength to the fibers of cotton. Option B, Glycogen, is incorrect because it is a storage polysaccharide found in animals, not plants. Option C, Wax, is incorrect as it refers to lipids that serve as protective coatings rather than structural fibers. Option D, Protein, is incorrect because proteins consist of amino acids and are not the primary structural component of cotton.

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

Explanation: The correct answer is Cellulose. Cellulose is a linear polymer composed of β-glucose units linked by β-1,4 glycosidic bonds, which provides the structural integrity necessary for plant cell walls. The other options do not fit the criteria:- Glycogen is primarily an energy storage molecule in animals, featuring α-1,4 and α-1,6 glycosidic linkages, not the β-1,4 linkages.- Amylopectin is a component of plant starch with a branched structure, containing α-1,4 and α-1,6 linkages, not the linear β-1,4 bonds.- Amylose is a component of starch that is a linear polymer with α-1,4 linkages, also lacking the β-1,4 glycosidic bonds.

• A. α-glucose
• B. β-glucose
• C. D-glucose
• D. L-glucose

Explanation: The correct answer is α-glucose. In the Haworth projection of glucopyranose, if the hydroxyl group attached to the anomeric carbon (carbon 1) is below the ring, it is termed α-glucose. Conversely, if the hydroxyl group is above the ring, it is termed β-glucose. Options C and D, D-glucose and L-glucose, refer to different stereoisomers of glucose based on the configuration of the chiral center farthest from the carbonyl group and are not directly related to the position of the hydroxyl group on the anomeric carbon.