At the most basic level of classification, cells can be either prokaryotic or eukaryotic.
Prokaryotic cells are only bacteria or archaea, eukaryotic cells are fungi, protists, plants and animals.
The key difference is that eukaryotes have a true nucleus and membrane-bound organelles. Prokaryotes lack a true nucleus and membrane-bound organelles. Prokaryotes are simple and are only ever unicellular.
the first answer as blood needs to be oxygenated to be passes round the body then when its deoxgenated it will return to the heart to be pumped around the body again
