- Metabolic energy production: Mannose acts as a dietary source of carbohydrates, providing energy to cells. It is first converted into glucose through various metabolic pathways, and eventually broken down into carbon dioxide and water, generating ATP (adenosine triphosphate) in the process.

- Glycoprotein formation: Mannose residues are commonly attached to proteins to form glycoproteins. Glycoproteins are essential components of cell membranes and play crucial roles in various cellular functions, including cell recognition, adhesion, signaling, and immune responses.

- Glycosaminoglycan synthesis: Mannose is a component of glycosaminoglycans (GAGs), which are long, unbranched polysaccharides attached to proteins to form proteoglycans. GAGs are found in the extracellular matrix and contribute to its structural integrity and function. For instance, hyaluronic acid, a GAG found in the synovial fluid of joints, contains mannose residues that contribute to its viscosity and shock-absorbing properties.

- Mannose 6-phosphate (M6P) pathway: Mannose 6-phosphate, formed by the addition of a phosphate group to carbon 6 of mannose, plays a vital role in targeting proteins to lysosomes. Proteins containing M6P are recognized and transported to lysosomes, where they participate in the degradation and recycling of various cellular components.

- Immune system regulation: Mannose receptors on immune cells, particularly macrophages, play a crucial role in recognizing and engulfing pathogens such as bacteria and viruses. This process is essential for the innate immune response and defense against infections.

- Plant cell wall component: In plants, mannose is present in the cell wall as a component of hemicellulose, a group of polysaccharides that provide structural support and flexibility to the plant cell wall.