Showing 81–90 of 96 questions
The enzyme RuBisCO catalyzes the fixation of CO2 by combining it with:
A
Glyceraldehyde-3-phosphate
B
Ribulose-1,5-bisphosphate
C
Phosphoenolpyruvate
D
Pyruvate
Correct Answer:
B. Ribulose-1,5-bisphosphate
Explanation:
RuBisCO (Ribulose-1,5-bisphosphate carboxylase/oxygenase) catalyzes CO2 fixation with RuBP in the Calvin cycle.
In the light-dependent reactions, the splitting of water molecules produces oxygen, hydrogen ions, and:
A
NADP+
B
NADPH
C
Electrons
D
ATP alone
Correct Answer:
C. Electrons
Explanation:
Water photolysis (2H2O → O2 + 4H+ + 4e-) releases electrons that are transferred through electron transport chains.
Which type of phloem tissue is responsible for translocation of sugars in plants?
A
Sieve tube members only
B
Companion cells only
C
Sieve tube members with companion cells
D
Phloem fibers
Correct Answer:
C. Sieve tube members with companion cells
Explanation:
Sieve tube members conduct sugars while companion cells provide ATP and metabolic support for active transport.
The osmotic potential of a solution is directly related to:
A
Temperature only
B
Solute concentration and temperature
C
Pressure only
D
Volume of solvent only
Correct Answer:
B. Solute concentration and temperature
Explanation:
Osmotic potential (Ψs) = -iCRT, where it depends on solute concentration (C) and absolute temperature (T).
In plant tissue culture, which growth regulator ratio promotes callus formation?
A
High auxin : Low cytokinin
B
Low auxin : High cytokinin
C
Equal ratio of auxin and cytokinin
D
Neither auxin nor cytokinin
Correct Answer:
A. High auxin : Low cytokinin
Explanation:
High auxin to low cytokinin ratio promotes callus formation, while the ratios determine the type of organogenesis.
The phenomenon of leaf fall in deciduous plants before winter is regulated by which hormone?
A
Abscisic acid
B
Ethylene
C
Gibberellin
D
Cytokinin
Correct Answer:
A. Abscisic acid
Explanation:
Abscisic acid (ABA) accumulates during water stress and environmental changes, promoting abscission layer formation and leaf fall.
Which of the following statements about stomatal opening is correct?
A
Guard cells lose turgor pressure when stomata open
B
Potassium ions accumulate in guard cells during stomatal opening
C
Stomata open in complete darkness
D
Guard cells have thick outer walls and thin inner walls
Correct Answer:
B. Potassium ions accumulate in guard cells during stomatal opening
Explanation:
During stomatal opening, potassium ions (K+) actively accumulate in guard cells, increasing osmotic potential and causing water influx.
The root pressure phenomenon in plants can be measured using a device called:
A
Potometer
B
Barograph
C
Manometer
D
Tensiometer
Correct Answer:
C. Manometer
Explanation:
Root pressure is measured using a manometer connected to the cut end of a plant stem, showing the positive pressure generated by roots.
In C4 plants, the first stable compound formed during carbon fixation is:
A
3-Phosphoglycerate
B
Oxaloacetate
C
Ribulose-1,5-bisphosphate
D
Glucose
Correct Answer:
B. Oxaloacetate
Explanation:
In C4 photosynthesis, CO2 combines with PEP (3-carbon) to form oxaloacetate (4-carbon compound) via the enzyme PEP carboxylase.
Universal blood donor group?
Explanation:
O- has no antigens, universal donor.
