Imagine if Cellulose and Starch Swapped Glycosidic Bond Bonding Patterns, Just For A Day…s

One common theme of BIOC223 and organic chemistry as well seems to be that the drastically, dramatically different differences that are relevant on a human scale can be attributed to the different ways elements can bond to each other. Elemental composition is almost meaningless in the organic chemistry and biochemical world – what gives us insight about function is the 3D structure, the network, and how these elements are bonded or interacting with one another. I think this is a pretty rad concept because it forces us to constantly rethink – it’s not just the building blocks that matter, its how the building blocks relate to each other! In this whole shpiel, I feel like I could have inserted a “parts are greater than the whole” comment somewhere.

Sticking with the week’s theme of carbohydrates, and also drawing from what we learned in today’s lecture, I wanted to show an example of what I mean by the relationship between the building blocks. Enter stage right: the difference between cellulose and starch. Both consist of glucose polymers, so one might initially expect them to have similar properties. However, because starch has alpha (1,4) glycosidic bonds and cellulose has beta (1,4) glycosidic bonds, that completely changes the geometry of the sugar polymers. Because of their different spatial arrangements, human enzymes cannot process cellulose (its linear shape won’t fit into the active site of the enzymes), though we can process starch.

So why is this relevant to humans?  Certainly this is an interesting topic,  because cellulose and starch crop up all over our favorite foods! Fruits and vegetables are often great sources of cellulose, while breads and potatoes are great sources of starch. Perhaps in a “perfect” world (for all those bread-lovers), we could swap the bonding pattern of starch and cellulose. Wouldn’t it be crazy to think might that pizza dough might have more health benefits than celery?