The anticoagulant heparin is used for blood gases and other chemistry tests. it works by:

Heparin acts as a cofactor for antithrombin. Antithrombin inhibits the formation of thrombin, which in turn inhibits the conversion of fibrinogen to fibrin. When fibrin is absent, platelet plugs which are unstable will eventually come apart, hence blood clotting does not occur.

The nucleoid is a specific region found exclusively within the cytoplasm of a prokaryotic cell. As it is an irregularly shaped region in the cytoplasm that encompasses and or contains DNA and proteins. This specific structure or area is not observed in the cytoplasm of eukaryotes.