All Free Biology MCQs with Answers

1271. Non polar organic molecules are ___________ in water?

• A. Soluble
• B. Insoluble
• C. Partially soluble
• D. Depends upon condition

Explanation: Nonpolar molecules do not form favourable interactions with polar water molecules, so they are generally insoluble and tend to aggregate away from water. This hydrophobic behaviour is important in the formation of lipid bilayers. Students may choose partially soluble because very small amounts can sometimes disperse, but the standard biological classification is insoluble in water.

1272. The survival of an animal depends upon its ability to take some from its environment____________?

• A. Chemicals
• B. Hydrocarbons
• C. Organic molecules
• D. Inorganic molecules

Explanation: Animals depend on obtaining organic molecules from the environment because these molecules supply energy and raw materials for growth, repair and metabolism. Inorganic substances such as water and mineral ions are also necessary, but the intended biological statement concerns the organic nutrients animals cannot generally manufacture from inorganic matter. Students may choose inorganic molecules because minerals and water are essential, but that overlooks the nutritional role of organic food molecules.

1273. In living organisms the lubricant which provides protection against damage resulting from friction is___________?

• A. Carbohydrates
• B. Fatty acid
• C. Water
• D. Protein

Explanation: Water acts as a lubricant in joints and other body surfaces, reducing friction and protecting tissues from mechanical damage. The likely alternative is protein, because collagen and other proteins support joints, but they are not the main lubricating substance.

1274. If a plasmolysed plant cell is placed in water the cell will___________?

• A. Burst
• B. Be Killed
• C. Be deplasmolysed
• D. Show no change in it

Explanation: Water enters a plasmolysed plant cell by osmosis because the cell sap has a lower water potential than the surrounding water. The protoplast expands and the cell becomes deplasmolysed, while the cell wall prevents bursting under normal conditions. Students may choose a by assuming that water uptake always makes a plant cell burst, ignoring the support provided by the cell wall.

1275. The major constituent of blood plasma is___________?

• A. Protein
• B. NaCl
• C. Water
• D. Cholesterol

Explanation: Water forms about 90 to 92% of blood plasma and acts as the solvent in which proteins, salts, nutrients, hormones and wastes are transported. Protein is the most abundant solid component of plasma, so students may select it while overlooking that water is the major constituent overall.

1276. Which statement is true about an aqueous medium________________?

• A. Ionic as well as non ionic substance in aqueous media retains their identity
• B. Enzymes can not perform catalysis reaction in this medium
• C. Ions and molecules move randomly thus are in more favorable state to react with other molecules and ions
• D. It is less favorable media for chemical reactions

Explanation: In an aqueous medium, dissolved ions and molecules move freely and randomly, increasing the opportunities for effective collisions and chemical reactions. Students may choose that aqueous media are less favourable, but water is the main solvent for most cellular reactions and allows enzymes to function.

1277. The number of calories required to raise the temperature of 1g of water from 15 to 16?C is called___________?

• A. Specific Heat of Vaporization
• B. Specific Heat capacity
• C. Caloric Heat
• D. Both A and C

Explanation: The heat needed to raise 1 g of water by 1 °C is one calorie, and this illustrates water's specific heat capacity, 1 cal/g°C. Students may choose caloric heat, but that is not the standard name for a substance's heat required per unit mass per degree.

1278. The property of water due to which it works as a temperature stabilizer and hence protect living organisms from sudden thermal changes is_______________?

• A. High specific heat of vaporization
• B. High specific heat capacity
• C. Its Dipole nature
• D. Its liquid state

Explanation: Water has a high specific heat capacity, so it absorbs or releases considerable heat with only a small change in its own temperature. This buffers sudden thermal changes in cells and organisms. Students often choose high specific heat of vaporization, which refers to the heat needed to convert water into vapour and mainly explains cooling by sweating or transpiration.

1279. Conversion of ammonia or ammonium ion into nitrites during nitrogen cycle occurs due_____________?

• A. Rhizobium
• B. Nitrosomonas
• C. Nitrobacter
• D. Pseudomonas

Explanation: Nitrosomonas carries out the first nitrification step, oxidizing ammonia or ammonium ions into nitrites. Nitrobacter performs the next step by converting nitrites into nitrates, so students may choose c when they reverse the two bacterial stages.

1280. Annual rainfall in grassland is about_____________?

• A. More than 2500 mm
• B. 750-1500 mm
• C. 250-750 mm
• D. Less than 250 mm

Explanation: Grasslands commonly receive about 250 to 750 mm of rainfall annually, enough to support grasses but usually insufficient for dense forests. Students may choose 750 to 1500 mm because they associate all productive vegetation with high rainfall, whereas that range more often supports wetter woodland or forest conditions.