Osmosis and active transportIB MYP Biology: Flashcards

Exam questions on Osmosis and active transport

1. The lungs contain millions of tiny air sacs called alveoli. Oxygen in the air inside each alveolus moves into the blood in the capillaries that surround it. During a race a runner in Nairobi breathes deeper and faster and her heart beats faster.
   Explain why deeper breathing and a faster heartbeat increase the rate at which oxygen enters her blood.2 marks
2. A student in Cape Town investigates osmosis in potato. She cuts five potato cylinders of the same length, each with a mass of 3.0 g. She places one cylinder in each of five beakers containing sugar solution of concentration 0.0, 0.2, 0.4, 0.6 and 0.8 mol dm⁻³. After 24 hours she blots each cylinder dry and weighs it again. The changes in mass were +0.4 g, +0.2 g, 0.0 g, −0.3 g and −0.5 g, in the same order as the concentrations.
   Explain why the potato cylinder in the 0.8 mol dm⁻³ solution lost mass.2 marks
3. Tomato plants grown on a farm in southern Spain begin to wilt after the irrigation water becomes very salty. The farmer also finds that the root hair cells of healthy plants take up nitrate ions from the soil, even though the concentration of nitrate in the soil is lower than the concentration inside the root hair cells.
   Explain why the tomato plants wilt when watered with very salty water.3 marks