You can also go to the other sides:
1) carbohydrate antigen
1. -- > entity
2. ---- > physical_object
3. ------ > inanimate
4. -------- > substance
5. ---------- > protein
6. ------------ > enzyme
7. -------------- > carbohydrate
8. ---------------- > carbohydrate antigen
9. ------------------ > antigen
10. -------------------- > carbohydrate antigen