Types of Compounds. Ionic compounds are compounds composed of ions, charged particles that form when an atom (or group of atoms, in the case of polyatomic ions) gains or loses electrons. 1  A cation is a positively charged ion. 2  An anion is a negatively charged ion.
Porins are members of an extended family of transmembrane proteins found in the outer membrane of gram negative bacteria such as E. coli, or in the outer membranes of mitochondria in eukaryotes. The general porins provide a simple diffusion pathway across the membrane for molecules less than 1 kDa with little substrate selectivity.
Heme B group of hemoglobin. An iron (Fe) atom in the middle is shown in red, complexed to four interior nitrogen atoms shown in blue. Porphyrins are a group of heterocyclic macrocycle organic compounds, composed of four modified pyrrole subunits interconnected at their Î± carbon atoms via methine bridges (=CHâ). The parent porphyrin is porphin, and substituted porphines are called porphyrins.