Protein glycosylation is a widespread post-translational modification found in all domains of life, playing crucial roles in protein folding, quality control, and biological recognition. Glycans, complex carbohydrate structures, add an additional layer of information to proteins, influencing their function and interactions. Advances in analytical techniques and biochemical approaches have enhanced our understanding of glycan diversity and their roles in vertebrates. Glycans on cell surfaces and intracellular proteins contribute to various functions, including cell adhesion, pathogen interaction, and signaling. They also affect protein secretion, endocytosis, and cellular processes like immune response and tumor metastasis. Glycans are used as markers for cellular compartments and cell type identification. The synthesis of glycans involves over 700 proteins, with glycosyltransferases playing a key role. Glycans can be attached through various linkages, including N-glycosylation, O-glycosylation, and C-mannosylation. N-glycans undergo processing in the secretory pathway, starting with high-mannose structures and progressing to complex forms. O-linked glycans, such as mucin-type and O-Man, have distinct structures and functions. Glycans also play roles in quality control, with specific enzymes regulating protein folding and degradation. The Golgi apparatus is central to glycan maturation, with enzymes distributed across its compartments. Glycan profiling techniques, including mass spectrometry and microarrays, are essential for understanding glycan diversity and their roles in health and disease. Protein domain-specific glycosylation highlights the importance of glycan modifications in biological recognition, with examples like EGF and TSR domains. The complexity of glycan structures presents challenges in analysis, but ongoing research continues to uncover their regulatory roles in biological systems.Protein glycosylation is a widespread post-translational modification found in all domains of life, playing crucial roles in protein folding, quality control, and biological recognition. Glycans, complex carbohydrate structures, add an additional layer of information to proteins, influencing their function and interactions. Advances in analytical techniques and biochemical approaches have enhanced our understanding of glycan diversity and their roles in vertebrates. Glycans on cell surfaces and intracellular proteins contribute to various functions, including cell adhesion, pathogen interaction, and signaling. They also affect protein secretion, endocytosis, and cellular processes like immune response and tumor metastasis. Glycans are used as markers for cellular compartments and cell type identification. The synthesis of glycans involves over 700 proteins, with glycosyltransferases playing a key role. Glycans can be attached through various linkages, including N-glycosylation, O-glycosylation, and C-mannosylation. N-glycans undergo processing in the secretory pathway, starting with high-mannose structures and progressing to complex forms. O-linked glycans, such as mucin-type and O-Man, have distinct structures and functions. Glycans also play roles in quality control, with specific enzymes regulating protein folding and degradation. The Golgi apparatus is central to glycan maturation, with enzymes distributed across its compartments. Glycan profiling techniques, including mass spectrometry and microarrays, are essential for understanding glycan diversity and their roles in health and disease. Protein domain-specific glycosylation highlights the importance of glycan modifications in biological recognition, with examples like EGF and TSR domains. The complexity of glycan structures presents challenges in analysis, but ongoing research continues to uncover their regulatory roles in biological systems.