In plant physiology, the 'Munch hypothesis' for the translocation of sugars in the phloem relies on the creation of a: MCQ with Answer and Explanation

In plant physiology, the 'Munch hypothesis' for the translocation of sugars in the phloem relies on the creation of a:
A. Transpiration pull
B. Cohesion-tension force
C. Root pressure
D. Turgor pressure gradient
Answer: Option D
Solution (By JKSSB Mock Tests)
The Munch hypothesis, or mass flow hypothesis, explains the movement of sugars (primarily sucrose) through the phloem. It proposes that sugars are actively loaded into the phloem at the source (e.g., leaves), which lowers the water potential and causes water to enter from the xylem by osmosis. This creates a high turgor pressure. At the sink (e.g., roots, fruits), sugars are unloaded, increasing water potential, and water leaves the phloem, creating a low turgor pressure. The bulk flow of sap is driven by this turgor pressure gradient from source to sink.

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Practice More Biology Questions

Question #1
The process of protein folding that is assisted by chaperone proteins occurs in the:
A. Lysosome
B. Golgi apparatus
C. Nucleus
D. Endoplasmic reticulum

Correct Answer: Option D


Explanation:
Chaperone proteins like BiP assist in proper protein folding in the rough ER. Misfolded proteins are degraded. Golgi modifies, lysosome digests.

This question belongs to: Science Biology
Question #2
In genetics, the 'Lac operon' is an example of a(n):
A. Inducible operon
B. Constitutive operon
C. Repressible operon
D. Attenuated operon

Correct Answer: Option A


Explanation:
The lac operon in E. coli is a classic example of an inducible operon. It is normally 'off' (repressed) because the lac repressor protein, produced by the 'i' gene, binds to the operator, preventing transcription of the structural genes (z, y, a) needed for lactose metabolism. However, when lactose is present in the environment, it is converted to allolactose, which acts as an inducer. Allolactose binds to the repressor, changing its shape and preventing it from binding to the operator, thus 'inducing' or allowing transcription to occur.

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Question #3
Which of the following is a correct statement about the structure of a neuron?
A. The myelin sheath speeds up impulse conduction by allowing continuous conduction.
B. Dendrites transmit impulses away from the cell body.
C. The cell body contains the nucleus and most organelles.
D. The axon receives impulses from other neurons.

Correct Answer: Option C


Explanation:
The soma (cell body) of a neuron contains the nucleus and metabolic machinery. Dendrites receive signals from other neurons and transmit them towards the soma, while the axon carries impulses away from the soma. The myelin sheath speeds up conduction by saltatory conduction (jumping between nodes), not continuous conduction.

This question belongs to: Science Biology