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Practice each question, then open the answer or worked solution.
Smaller, lipid-soluble molecules diffuse faster through the cell membrane,
but the movement of hydrophilic substances are facilitated by certain
transporters which are chemically ____________.
Smaller, lipid-soluble molecules diffuse faster through the cell membrane, but the movement of hydrophilic substances are facilitated by certain transporters which are chemically proteins.
In passive transport across a membrane, when two different molecules
move in the opposite direction and independent of each other, it is called
___________.
Antiport
Osmosis is a special kind of diffusion, in which water diffuses across the
cell membrane. The rate and direction of osmosis depends upon
both ______________.
Pressure and concentration gradient
A flowering plant is planted in an earthen pot and irrigated. Urea is
added to make the plant grow faster, but after some time the plant dies.
This may be due to _______________ .
Exosmosis
Absorption of water from the soil by dry seeds increases the _____________,
thus helping seedlings to come out of the soil
Pressure
Water moves up against gravity and even for a tree of 20m height, the tip
receives water within two hours. The most important physiological
phenomenon which is responsible for the upward movement of water is
_______________________.
Transpiration pull
The plant cell cytoplasm is surrounded by both cell wall and cell
membrane. The specificity of transport of substances are mostly across
the cell membrane, because _________________.
The cell wall is freely permeable to water and substances in solutions but the membrane is selectively permeable.
The C4 plants are twice as efficient as C3 plants in terms of fixing CO2 but
lose only _________ as much water as C3 plants for the same amount of
CO2 fixed.
Half.
In a plant, translocation in the xylem is unidirectional while in phloem it is
bidirectional. Explain.
The vascular bundle, phloem is responsible for conducting the food from the source to the sink. But the process is reversed during seasons like spring because during that term the food which is stored in the sink is then supplied to the growing parts of the plant. The source and sink relation are hence variable so the direction of movement of food via the phloem can be either upwards or downwards i.e. bidirectional.
Identify the process occurring in I, II and III
I) Uniport
II) Antiport
III) Symport