Most fungal carbohydrate metabolism is via glycolysis and the tricarboxylic acid cycle, although both fermentative pathways and anaerobic pathways have been found in specialized fungi. Fungi cannot fix gaseous nitrogen. They can however utilize nitrate, ammonia and some amino acids by direct uptake across the hyphal membrane. More complex nitrogen sources, such as proteins and peptides, can be utilized. Fungi require both macro and micronutrients, but these are usually available to excess in their environments, and some fungi may have other requirements, for example thiamin and biotin, sterols, riboflavin, nicotinic acid and folic acid.
Fungi are capable of the formation and secretion of many types of secondary metabolites.
These compounds can be produced by many different metabolic pathways. The living part of a fungus consists of the apical cell of the mycelium and a few cells that are immediately behind it. Cells that are beyond about 5 cross walls, that is septae, and usually moribund unless they have special survival functions. The septae that separate the cells are usually perforate, and have varying structures to protect the cell from loosing its contents if there was a disruption of a neighbouring cell. In the Ascomycetes the septae are protected by a Woronin body, an osmophilic oily structure which can plug the septum if required, or in the Basidiomycetes there is a complex wall structure to the septum and also a complex of endoplasmic reticulum associated with the septal pore.