Cell theory is the guess that all living organisms are made of cells.A cell needs another cell to survive if you are wondering where the first cell came from I can not tell you it depends on your beliefs.

Eukaryotas  means the cells have a nucleus. Prokaryotes  means the cells have no nucleus.

There are different types of cells,plant cells,animal cells,and fungal cells.

Heterotrophic means that the organism go to eat food. Autotrophic means they make food themselves.

And that is cell theory.

A mixture is 2 or more substances combined physically but not chemically and keeps its own property.

A compound is two substances chemically combined.

An element is a pure substance the building blocks of matter.