Practice important
Swelling Pressure
MCQ questions and answers.
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MCQ Questions
1. A dry seed is enclosed in a rigid, water-impermeable chamber and allowed to contact liquid water through a porous support. Which observation most directly demonstrates swelling pressure?
A.
The seed develops pressure against the chamber walls while absorbing water
B.
The seed loses solutes into the chamber without changing volume
C.
The seed develops pressure only after chlorophyll formation
D.
The seed absorbs water only when its cells are metabolically active
Correct Answer:
The seed develops pressure against the chamber walls while absorbing water
Explanation:
Swelling pressure is the pressure developed when an imbibant, such as a dry seed, takes up water and tends to increase in volume. A rigid enclosure converts this tendency to swell into measurable pressure.
2. Which change would most likely increase the swelling pressure produced by an equal mass of a dry, finely powdered hydrophilic colloid placed in water?
A.
Increasing the particle size while keeping the chemical composition unchanged
B.
Increasing the exposed surface area by reducing the material to finer particles
C.
Replacing the hydrophilic colloid with a nonpolar substance
D.
Preventing contact between the colloid and water while maintaining atmospheric humidity
Correct Answer:
Increasing the exposed surface area by reducing the material to finer particles
Explanation:
Swelling pressure depends on the interaction between water and hydrophilic surfaces. Finer particles expose a greater total surface area, allowing more extensive imbibition and a stronger swelling tendency.
3. A dry wooden beam is tightly fitted between two masonry walls. After prolonged wetting, the beam pushes the walls apart. The immediate physical cause is best described as
A.
swelling pressure generated by imbibition of water by hydrophilic cell-wall materials
B.
osmotic pressure generated exclusively by living wood cells
C.
root pressure transmitted through the beam
D.
turgor pressure produced by actively photosynthesizing tissues
Correct Answer:
swelling pressure generated by imbibition of water by hydrophilic cell-wall materials
Explanation:
Cellulose and other hydrophilic components of wood imbibe water and expand. When expansion is mechanically constrained, the resulting force appears as swelling pressure.
4. Which statement most accurately distinguishes swelling pressure from osmotic pressure in a dry seed during initial water uptake?
A.
Swelling pressure arises from water attraction by hydrophilic colloids, whereas osmotic pressure requires solute concentration across a selectively permeable membrane
B.
Swelling pressure is produced only by dissolved salts, whereas osmotic pressure is produced by cellulose
C.
Swelling pressure requires living membranes, whereas osmotic pressure occurs only in dead tissues
D.
Swelling pressure always expels water, whereas osmotic pressure always prevents water movement
Correct Answer:
Swelling pressure arises from water attraction by hydrophilic colloids, whereas osmotic pressure requires solute concentration across a selectively permeable membrane
Explanation:
Swelling pressure is a consequence of imbibition by hydrophilic colloids such as cell-wall polysaccharides and seed colloids. Osmotic pressure is related to solute concentration and selective membrane properties, so the two mechanisms are distinct.
5. A seed coat is experimentally made less permeable to water, while the hydrophilic composition and mechanical strength of the embryo remain unchanged. What is the most likely initial effect on swelling pressure inside the seed?
A.
It will develop more slowly because water reaches the imbibing colloids less readily
B.
It will become independent of water availability
C.
It will immediately become zero because hydrophilic colloids cannot attract water
D.
It will increase instantly because reduced permeability concentrates all water outside the seed
Correct Answer:
It will develop more slowly because water reaches the imbibing colloids less readily
Explanation:
Swelling pressure is generated during water uptake by hydrophilic materials. Lower seed-coat permeability restricts water entry and therefore delays the development of swelling pressure, although it does not eliminate the intrinsic swelling capacity.
6. Why can imbibition by dry seeds rupture a hard seed coat or crack surrounding soil, even though no metabolic energy is initially required?
A.
Hydrophilic colloids absorb water and develop swelling pressure that can exceed the tensile strength of the surrounding material
B.
Water hydrolyses every structural polymer before entering the seed
C.
The seed first produces ATP, which is directly converted into mechanical force
D.
Dissolved oxygen accumulates inside the seed and creates the mechanical pressure
Correct Answer:
Hydrophilic colloids absorb water and develop swelling pressure that can exceed the tensile strength of the surrounding material
Explanation:
Imbibition is driven by attraction between water and hydrophilic colloids, not necessarily by metabolism. The associated expansion can generate swelling pressure large enough to rupture seed coverings or displace soil particles.
7. Two equal-sized dry seed samples contain different amounts of hydrophilic colloidal material. Under identical conditions, sample X produces greater swelling pressure than sample Y. Which inference is most justified?
A.
Sample X likely has a greater effective hydrophilic surface or a greater capacity to bind water
B.
Sample X must have a higher chlorophyll concentration
C.
Sample Y must have greater osmotic pressure because it swells less
D.
Sample X must be absorbing water through active transport at a higher rate
Correct Answer:
Sample X likely has a greater effective hydrophilic surface or a greater capacity to bind water
Explanation:
The magnitude of swelling pressure is related to the amount and accessibility of hydrophilic colloidal material and its affinity for water. Greater swelling does not by itself prove greater metabolic activity or active transport.
8. A dry gelatinous material is allowed to imbibe water freely and is then placed in a rigid container. Compared with the same material in an unconstrained beaker, the rigid container will primarily cause
A.
more of the swelling tendency to appear as pressure against the container
B.
complete prevention of water binding by the material
C.
conversion of swelling pressure into osmotic pressure
D.
loss of all hydrophilic groups from the material
Correct Answer:
more of the swelling tendency to appear as pressure against the container
Explanation:
When an imbibant is unconstrained, much of its water uptake appears as expansion. Mechanical restriction opposes expansion, so the swelling tendency is expressed as pressure on the surrounding container.
9. Which experimental result would provide the strongest evidence that a pressure developed by a dry plant material is swelling pressure rather than pressure caused by living-cell metabolism?
A.
A killed, dried material still absorbs water and exerts pressure on a confining piston
B.
The pressure disappears when the material is supplied with oxygen
C.
The pressure appears only in green tissues exposed to light
D.
The pressure is abolished by inhibiting cellular respiration before water contact
Correct Answer:
A killed, dried material still absorbs water and exerts pressure on a confining piston
Explanation:
Swelling pressure is a physical consequence of imbibition by hydrophilic colloids and can occur in nonliving material. Demonstrating it in killed, dried tissue separates it from pressure dependent on cellular metabolism.
10. A dry hydrophilic sample is compressed so that its particles are packed more tightly, but its chemical composition remains unchanged. If water can still reach all exposed surfaces, which outcome is most plausible during initial imbibition?
A.
The external swelling pressure may rise because expansion is more strongly mechanically opposed
B.
Swelling pressure must disappear because compression destroys all water-attracting sites
C.
The sample must produce osmotic pressure even without a selectively permeable barrier
D.
The sample cannot imbibe water because physical compression prevents molecular attraction
Correct Answer:
The external swelling pressure may rise because expansion is more strongly mechanically opposed
Explanation:
Swelling pressure is the mechanical expression of an imbibant's tendency to expand during water uptake. Greater external constraint can cause a larger pressure to be registered, provided water can still contact the hydrophilic surfaces.
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