The glycome is the collective identity of the entirety of carbohydrates in an organism. The glycome may in fact be one of the most complex entities in nature. The glycome is studied by glycobiology sometimes referred to as glycomics.
The genome is one of the most complex structures in an organism (although not necessarily as complex as, for example, the brains of higher organisms). The genome is responsible for the proteome, which is more complex than the genome by virtue of the fact that it combines the complexity of the genome with the complexity of the proteins which the genome specifies, proteins whose characteristics are at least partially determined by the phenomenon of molecular folding, which is one of the most complex phenomena known to science.
The glycome exceeds the complexity of the proteome as a result of the even greater diversity of the glycome's constituent carbohydrates and is further complicated by the sheer multiplicity of their possibilities of combination and interaction of the carbohydrates with each other and with proteins.
An alternative definition is the collective identity of the entirety of carbohydrates in a cell. In those definitions, the word sugar, the word glycan and the word polysaccharide can be meaningfully substituted for carbohydrate.
Ajit Varki, professor of medicine and cell and molecular biology, and director of the Glycobiology Research and Training Center at the University of California, San Diego has illustrated the scale of the glycome challenge by claiming that the glycome is:
There is a pivotal body in this field, called the Consortium for Functional Glycomics (CFG) funded by the (US) National Institute of General Medical Sciences. This body (which operates in a field called glycosciences ) includes participants in 'glycome projects' within its remit. The US Federal grant which can be said to have 'put the glycome on the political map' was described as a 'glue grant' of $34M (for the formation of the CFG, see above).