IB myp 4-5 Biology – Practice Questions- All Topics
Topic :Metabolism-Osmosis
Topic :Metabolism– Weightage : 21 %
All Questions for Topic : Nutrition,Digestion,Biochemistry and enzymes,Movement and transport,Diffusion,Osmosis,Gas exchange,Circulation,Transpiration and Translocation,Homeostasis
Experiment
A model cell only needs to have a membrane and cytoplasm for osmosis to occur. The membrane can be made out of the PVC film that is used to seal food items (known as plastic wrap or cling
film). It is about 10 μm thick, whereas a cell membrane is 10 nm thick.
Question:
What is the size ratio between the thickness of a cell membrane and that of the plastic film?
▶️Answer/Explanation
Ans: 10 micrometres/μm to 10 nanometres/nm; 10 micrometres = 10,000 nanometres; ratio is 1,000 to 1.
Question:
In Samuel Coleridge Taylor’s poem The Rime of the Ancient Mariner there are these words:
If someone on a boat is dying of thirst and they drink seawater, the osmolarity of their blood plasma becomes higher, not lower. Can you explain this using your understanding of osmosis?
▶️Answer/Explanation
Ans: Seawater has a higher solute concentration than blood plasma/body fluids; therefore seawater in the gut causes water to be removed from the wall of the gut/body tissues by osmosis; so the
concentration of solutes in the plasma is increased.
Question:
Plasma proteins are a major component of the osmolarity of blood plasma. Children who are suffering from severe protein malnutrition develop swollen abdomens due to retention of excessive amounts of water in their tissues. Can you explain this?
▶️Answer/Explanation
Ans: Dissolved proteins in blood plasma help excess water to be drawn out of tissues; by osmosis; so fluid does not accumulate in body tissues; without these plasma proteins the solute concentration of blood plasma is reduced; so excess water remains in the tissues; and they become swollen.