Several examples of substances crossing membranes are shown below. 1 glucose molecules into the epithelium lining the small intestine 2 nitrate ions from a dilute soil solution into a solution of higher concentration in root hair cells 3 water molecules from mesophyll cells to the air spaces within a leaf For which of these examples is oxygen required?
- A1, 2 and 3
- B1 and 2 only
- C1 and 3 only
- D2 and 3 only