WaterAQA A-Level Biology: Mind map

Exam questions on Water

1. The small intestine digests a meal containing starch, protein and lipid, and the products are absorbed into cells where they are built into new polymers. All of these reactions take place in aqueous solution.
   Maltose is hydrolysed by the enzyme maltase in the small intestine. Describe what happens to the maltose molecule in this reaction.2 marks
2. A pond in summer contains fish, algae and pond skaters (insects that walk across the surface of the water without sinking). During one day the air temperature above the pond rises by 15 °C but the temperature of the water rises by only 3 °C.
   Explain why the temperature of the pond water changes less than the temperature of the air, and why this is an advantage to the organisms living in the pond.2 marks
3. A tall oak tree transports water from its roots to its leaves in xylem vessels. In full sunlight each leaf absorbs 1.20 kJ of energy per minute from the Sun, which would otherwise heat it. The energy needed to evaporate 1 g of water from a leaf is 2.4 kJ.
   Explain how the strong cohesion between water molecules helps the tree to transport water up to its leaves.3 marks