They fix nitrogen from dinitrogen (N2) in the air using the enzyme nitrogenase, in order to provide the cells in the filament with nitrogen for biosynthesis. Nitrogenase is inactivated by oxygen, so the heterocyst must create a microanaerobic environment.
Vitamin B12 is an especially important vitamin for maintaining healthy nerve cells, and it helps in the production of DNA and RNA, the body's genetic material. Vitamin B12 works closely with vitamin B9, also called folate or folic acid, to help make red blood cells and to help iron work better in the body.
B-7 (biotin) is used in sugar metabolism and used clinically to improve the health of hair. Doctors might recommend a B complex to help boost energy, help with depression and even help with sugar cravings. It is not a far stretch to assume B vitamins could help us feel better since they are needed for so many functions in the body. At times, one member of the B family may be more important than others. B-3 for cholesterol is one example.