Free Biological Molecules MCQs with Answers
1,790 Biological Molecules MCQs from Biology, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
The chapter covers water's polarity and biological roles, carbohydrates, lipids, proteins and nucleic acids, including their monomers, bonds, structures and functions. It also distinguishes RNA from DNA and explains conjugated molecules such as glycoproteins, glycolipids and nucleoproteins, which combine organic molecules with a non-protein component.
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121. The pressure generated when water enters & inflates plant cells is called ___________ potential?
- A. Water
- B. Osmotic
- C. Pressure
- D. Solute
Explanation: When water enters a plant cell, it pushes the plasma membrane against the cell wall and produces turgor pressure, represented as pressure…
Correct answer: Pressure- A. Three
- B. Four
- C. Two
- D. Five
Explanation: The two major components used for plant water potential are solute potential and pressure potential, expressed as Ψw = Ψs + Ψp.
Correct answer: Two- A. Tonoplast
- B. Apoplast
- C. Symplast
- D. Vacuolar.
Explanation: The apoplast is the continuous pathway through cell walls and intercellular spaces, but the Casparian strip blocks it at the endodermis.
Correct answer: Apoplast124. The diffusion of ions along with water also takes place by mass flow system along the ________ path?
- A. Tonoplast
- B. Apoplast
- C. Symplast
- D. Vacuolar
Explanation: Mass flow through cell walls and intercellular spaces occurs along the apoplast pathway, which does not require water to cross plasma…
Correct answer: Apoplast- A. Root hairs
- B. Root cells
- C. Underground stem
- D. All of these
Explanation: Root hairs greatly increase the surface area in contact with the soil and have thin walls, making them the main sites for water and…
Correct answer: Root hairs126. There are __________ types of nutrients needed by plants besides light to carry out photosynthesis
- A. Two
- B. Three
- C. Four
- D. Five
Explanation: In the usual school-level description, photosynthesis requires three materials besides light: water, carbon dioxide and chlorophyll, which…
Correct answer: Three- A. Large number of vacoules in a plant cell.
- B. Higher ionic concentration inside vacuoles resulting from active pumping of ions at their tonoplastic membrane
- C. Higher osmotic pressure of the cell vacuole
- D. both b and c
Explanation: Active pumping of ions into the vacuole increases its solute concentration and therefore its osmotic pressure, drawing in water and…
Correct answer: both b and c- A. Vitamin B and C
- B. Vitamin B and D
- C. Vitamin C and B
- D. Vitamin A and B
Explanation: Scurvy results from vitamin C deficiency, while beri-beri results from vitamin B1, or thiamine, deficiency.
Correct answer: Vitamin C and B- 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…
Correct answer: Insoluble130. 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…
Correct answer: Organic molecules- 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.
Correct answer: Water- 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.
Correct answer: Be deplasmolysed- 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…
Correct answer: Water- 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…
Correct answer: Ions and molecules move randomly thus are in more favorable state to react with other molecules and ions- 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.
Correct answer: Specific Heat capacity- 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.
Correct answer: High specific heat capacity137. 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.
Correct answer: Nitrosomonas- 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…
Correct answer: 250-750 mm- A. CO2
- B. O2
- C. Water
- D. Nutrients
Explanation: Aquatic ecosystem productivity depends strongly on available light for photosynthesis and on nutrients such as nitrates and phosphates…
Correct answer: Nutrients- A. Tropical rain forest
- B. Temperate deciduous forest
- C. Grassland
- D. Tundra
Explanation: Pakistan contains grasslands, temperate deciduous forests and cold high-altitude regions that may be classified as tundra, but it does not…
Correct answer: Tropical rain forest