IGCSE Biology Paper-4: Specimen Questions with Answers 124 - 126 of 279

Passage

Fig. is a photomicrograph of part of a cell from the pancreas that produces enzymes that are released into the small intestine.

The Photomicrograph

Question 124 (2 of 2 Based on Passage)

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Structure D is part of the nucleus of the cell.

State one function of a nucleus.

Explanation

Some of the main functions of the nucleus include:

  • Protein synthesis, cell division, and differentiation
  • Control the synthesis of enzymes involved in cellular metabolism
  • Controlling hereditary traits of the organism
  • Store DNA strands, proteins, and RNA
  • Site of RNA transcription - e. g. mRNA required for protein synthesis

Question 125

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Lack of protein in the diet can result in protein-energy malnutrition.

State the name of one disease caused by protein-energy malnutrition.

Explanation

Difference between Kwashiorkor and Marasmus

Passage

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

Question 126 (1 of 7 Based on Passage)

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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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