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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- A. Cabbage
- B. Lady finger(okra)
- C. Cassava
- D. Non of these
Explanation: Lady finger, or okra, contains approximately 90% water, although the exact value varies with variety and measurement method.
Correct answer: Lady finger(okra)- A. Hydrophytes
- B. Mesophytes
- C. Xerophytes
- D. Halophytes
Explanation: Xerophytes are plants adapted to dry habitats and commonly have a thick, waxy cuticle that reduces evaporation from leaf surfaces.
Correct answer: Xerophytes- A. Hydrophytes
- B. Mesophytes
- C. Xerophytes
- D. Halophytes
Explanation: Rose grows best where water is reasonably available but not continuously abundant, so it is classified as a mesophyte.
Correct answer: Mesophytes- A. Diffusion
- B. Active transport
- C. Osmosis
- D. All of these
Explanation: Light activates ion transport mechanisms in guard cells, and K+ is accumulated from surrounding cells by active transport.
Correct answer: Active transport- A. Increases.
- B. Lowers.
- C. Doesn't effect.
- D. Maintains.
Explanation: Adding salts and other solutes makes the xylem sap more concentrated, which lowers its water potential.
Correct answer: Lowers.- A. Bacteria
- B. Viruses
- C. Fungi
- D. Cyanobacteria
Explanation: Mycorrhizal fungi form symbiotic associations with plant roots and extend fungal hyphae through the soil, increasing the area from which…
Correct answer: Fungi- A. Opening
- B. Closure
- C. Both of these
- D. None of these
Explanation: Low carbon dioxide concentration, especially inside the leaf, promotes stomatal opening so that more CO2 can enter for photosynthesis.
Correct answer: Opening- A. One
- B. Two
- C. Three
- D. Four
Explanation: The two commonly taught explanations for stomatal movement are the starch-sugar hypothesis and the potassium-ion hypothesis.
Correct answer: Two- A. Temperature
- B. pH
- C. Light
- D. None of these
Explanation: Light directly stimulates guard cells to accumulate solutes, causing water to enter and increasing their turgor, which opens the stomatal…
Correct answer: Light- A. Lenticels
- B. Guard cells
- C. Hydathods
- D. All of these
Explanation: Guard cells surround each stomatal pore and act as a turgor-controlled hydraulic valve, opening or closing the pore as water enters or…
Correct answer: Guard cells- A. 90%
- B. 91%
- C. 93%
- D. 95%
Explanation: Stomata are the main pathway for water vapour leaving a leaf, so stomatal transpiration is commonly estimated at about 90% of total…
Correct answer: 90%- A. Transpiration pull
- B. Root pressure
- C. Osmotic pressure.
- D. None of these
Explanation: Root pressure develops when root cells actively accumulate salts in the xylem, lowering the xylem water potential and drawing water into…
Correct answer: Root pressure- A. A big pore
- B. Stoma
- C. Sponge
- D. Cars or small protusions
Explanation: Lenticels are small, raised or slightly protruding porous areas in the bark that permit gas exchange.
Correct answer: Cars or small protusions- A. Hydathods
- B. Stomata
- C. Lenticels
- D. None of these
Explanation: Lenticels are aerating pores in the bark that allow oxygen and carbon dioxide exchange and permit some water loss as vapour.
Correct answer: Lenticels- A. 2-3%
- B. 1-3%
- C. 1-4%
- D. 1-2%
Explanation: Lenticular transpiration through bark lenticels is usually about 1% to 2% of total transpiration, so option d gives the standard…
Correct answer: 1-2%- A. 6-8%
- B. 5-7%
- C. 7-9%
- D. 4-6%
Explanation: Cuticular transpiration is commonly estimated at about 5% to 7% of total transpiration, giving option b.
Correct answer: 5-7%117. Exceptionally the positive hydrostatic pressure generated by root pressure is about___________?
- A. 600 Kpa
- B. 800 Kpa
- C. 1000 Kpa
- D. 900 Kpa
Explanation: Exceptional root pressure is commonly stated to reach about 800 kPa, meaning a positive pressure of 800 kPa in the xylem.
Correct answer: 800 Kpa- A. 8mh-1
- B. 1 mh-1
- C. 7 mh-1
- D. 4 mh-1
Explanation: In many plants other than very tall trees, the upward movement of water is commonly given as about 1 m h^-1.
Correct answer: 1 mh-1- A. Osmotic
- B. Pressure
- C. Both of these
- D. None of these
Explanation: Osmotic or solute potential measures the change in water potential caused by dissolved solute particles, which lower the water potential…
Correct answer: Osmotic- A. Deffusion
- B. Osmosis
- C. Active transport
- D. None of these
Explanation: Osmosis is the net movement of water through a selectively permeable membrane from higher water potential to lower water potential.
Correct answer: Osmosis