IGCSE Biology Paper-4: Specimen Questions with Answers 132 - 132 of 279

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Passage

Plants produce glucose in leaves and convert some of it to sucrose.

Question 132 (7 of 7 Based on Passage)

Write in Short

Short Answer▾
Sucrose Solution

The arrows show the direction of the movement of the liquids.

Fig. shows the position of the colored sucrose solution 45 minutes after the apparatus was set up.

Movement of Sucrose Solution
  • Partially permeable bags were attached tightly to the ends of tube X.
  • The bag representing a source was filled with a colored sucrose solution.
  • The bag representing a sink was filled with water.
  • The containers and tube X and tube Z were filled with water.

Fig. shows the apparatus used to model the movement of sucrose in a plant:

The movement of sucrose in plants can be modelled using laboratory apparatus.

Explain why the sucrose solution moves along tube X in the model in Fig.

Explanation

Two bags are bounded by semipermeable membrane and are interconnected by tube X. They are now dipped in same solution with different condition. It is assumed that initially entire system is filled with water and is at equilibrium. If sugar is added in one of the bags its osmotic pressure and suction pressure increase, as a result water enters it by the process of endosmosis. This causes an increase in the turgor pressure, due to which water starts flowing in. The water molecules also carry solutes along with them. This movement of water and sugar molecules will continue until the concentration of entire system becomes uniform and will stop once a state of equilibrium is achieved. But if sugar molecules are either removed or converted into starch, the movement will continue endlessly.

Semi Permeable Membrane

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