The phenomenon where plants lose water in liquid form through hydathodes is called:
A
Transpiration
B
Guttation
C
Exudation
D
Imbibition
Correct Answer:
B. Guttation
Guttation occurs when root pressure forces water out through hydathodes (water pores) as liquid water droplets, typically at night.
The grana in chloroplasts are composed of:
A
Stacked thylakoids
B
Unstacked thylakoids
C
Stroma lamellae
D
Cristae
Correct Answer:
A. Stacked thylakoids
Grana are stacks of thylakoids arranged vertically, while stroma lamellae are unstacked thylakoids connecting different grana.
The Q10 value for enzyme-catalyzed reactions is typically:
A
1.0-2.0
B
2.0-3.0
C
3.0-4.0
D
4.0-5.0
Correct Answer:
B. 2.0-3.0
Q10 of 2.0-3.0 indicates that enzyme activity doubles or triples with every 10°C increase in temperature, typical for biological systems.
In the Calvin cycle, which enzyme catalyzes the fixation of CO2?
A
Ribulose-1,5-bisphosphate carboxylase (RuBisCO)
B
Phosphofructokinase
C
Aldolase
D
Transketolase
Correct Answer:
A. Ribulose-1,5-bisphosphate carboxylase (RuBisCO)
RuBisCO is the most abundant enzyme on Earth and catalyzes the carboxylation of RuBP with CO2 in the dark reactions.
During photosynthesis, the splitting of water molecules occurs in which compartment of the chloroplast?
A
Stroma
B
Thylakoid lumen
C
Outer membrane
D
Inner membrane
Correct Answer:
B. Thylakoid lumen
Water photolysis (photosystem II) occurs in the thylakoid lumen where oxygen is released as a byproduct.
A student observes that a plant kept in a completely dark room still shows some gas exchange. This can be attributed to:
A
Photorespiration
B
Aerobic respiration
C
Fermentation
D
Chemosynthesis
Correct Answer:
B. Aerobic respiration
In darkness, photosynthesis stops, but aerobic respiration continues, consuming O2 and releasing CO2, resulting in measurable gas exchange.
Which hormone is primarily responsible for closing stomata under water stress conditions?
A
Gibberellin
B
Abscisic acid (ABA)
C
Auxin
D
Cytokinin
Correct Answer:
B. Abscisic acid (ABA)
ABA accumulates in guard cells during water stress and causes stomatal closure by reducing turgor pressure in guard cells.
In C4 photosynthesis, the primary CO2 acceptor molecule is:
A
Oxaloacetate
B
Phosphoenolpyruvate (PEP)
C
3-Phosphoglycerate
D
Ribulose-1,5-bisphosphate
Correct Answer:
B. Phosphoenolpyruvate (PEP)
In C4 plants, CO2 first combines with PEP (3-carbon molecule) to form oxaloacetate (4-carbon), which is why it's called C4 photosynthesis.
The rate of transpiration is LEAST affected by which of the following factors?
A
Light intensity
B
Soil pH
C
Relative humidity
D
Temperature
Correct Answer:
B. Soil pH
Soil pH has minimal direct effect on transpiration rate. Primary factors affecting transpiration are light, humidity, temperature, and wind velocity.
Which of the following is the primary pigment involved in capturing light energy during photosynthesis?
A
Chlorophyll a
B
Chlorophyll b
C
Xanthophyll
D
Carotenoid
Correct Answer:
A. Chlorophyll a
Chlorophyll a is the primary pigment that directly participates in the photochemical reactions of both PSI and PSII, while other pigments act as accessory pigments.
