1. Name some substances that move into and out of cells.
Answer
Into cells: glucose, amino acids, oxygen.
2. What does "partially permeable" mean ?
Answer
Only lets certain substances (or molecules) through.
3. Plants require mineral ions for healthy growth. Where do plants get mineral ions from ?
Answer
They absorb them (into root hair cells) from the soil.
4. Compare the surface area to volume ratio of a single-celled organism with the surface area to volume ratio of a large multicellular organism.
Answer
A single-celled organism has a relatively large surface area to volume ratio whereas a large multicellular organism has a relatively small surface area to volume ratio.
5. Explain how large multicellular organisms, such as mammals, obtain the oxygen they need to carry out aerobic respiration.
Answer
Mammals have a breathing system where oxygen diffuses into the blood and a transport circulatory system to take the oxygen to the body cells.
6. The lungs of a mammal are adapted for gas exchange. Describe two ways that a concentration gradient is maintained in the lungs.
Answer
Network of capillaries give rich blood supply. Ventilation (breathing) provides supply of fresh air.
7. A student investigates osmosis using "bags" made from an artificial partially permeable membrane. He fills three bags with 10 cm3 of 5% sugar solution, records their masses, places each in a different sugar solution concentration, waits 30 minutes, then reweighs the bags to observe mass changes due to osmosis. The figure below shows how the student sets up the apparatus. Explain what will happen to the masses of the bags.
Answer
Tube A will gain mass because water will move into the bag by osmosis from a more dilute to a more concentrated solution. Tube B mass will stay the same because same concentration inside and outside the bag so no net movement of water by osmosis. Tube C will lose mass because water moves out of the bag by osmosis from a more dilute to a more concentrated solution.
8. Describe two similarities between diffusion and osmosis.
Answer
Both are passive processes (do not require energy) and involve the movement of substances down a concentration gradient.
9. The figure below shows a root hair cell. How are mineral ions transported into root hair cells from a more dilute soil solution, and how do abundant mitochondria enhance this uptake ?
Answer
Ions are transported via active transport. Aerobic respiration occurs in the mitochondria, releasing energy that enables the movement of mineral ions against their concentration gradient.