Consider starch and fiber, both polysaccharides, both derived from plants, both composed of hundreds to thousands of monosaccharides joined together, but they're joined together differently, and that changes the effect  they have on your body.
Considera l'amido e le fibre, entrambi polisaccaridi, entrambi di origine vegetale, entrambi composti di centinaia di migliaia di monosaccaridi legati tra loro, però legati diversamente, causando così un effetto diverso sul tuo corpo.