Nucleus:
- The nucleus is a membrane-bound organelle that contains the genetic material of a cell.
- In Amoeba proteus, the nucleus is present and plays a crucial role in controlling cellular functions such as growth, metabolism, and reproduction.
- However, in Entamoeba histolytica, the nucleus is absent. Instead, it possesses a small, compact structure called the karyosome, which is thought to function similarly to a nucleus.

Food Vacuole:
- Food vacuoles are membrane-bound structures involved in the digestion and storage of food particles in amoebas.
- In Amoeba proteus, food vacuoles are present and are responsible for engulfing and breaking down food particles.
- In contrast, Entamoeba histolytica lacks well-developed food vacuoles. Instead, it relies on absorption through the cell membrane to obtain nutrients.

Contractile Vacuole:
- Contractile vacuoles are organelles responsible for regulating water balance in amoebas by expelling excess water from the cell.
- Amoeba proteus possesses contractile vacuoles that periodically contract to remove excess water and maintain osmotic balance.
- Entamoeba histolytica, on the other hand, does not have contractile vacuoles. This adaptation allows it to survive in low-nutrient environments and contributes to its pathogenicity.

Conclusion:
In summary, Entamoeba histolytica differs from Amoeba proteus due to the absence of a nucleus, the presence of a karyosome, the lack of well-developed food vacuoles, and the absence of contractile vacuoles. These differences in cellular structures and functions contribute to the distinct characteristics and adaptations of Entamoeba histolytica as a parasitic amoeba.