the difference between sugar the food and blood sugar?

Question

I dont know why but this is one of those things I just cant make sense of even with Google. So is sugar found in blood and the body there from eating sugar or a natural accurance regardless of diet? Is sugar as a food and blood sugar completly seperate things? This has bothered me for 2 decades. Explain it like I am 3 please.

In: Biology

Answer 1

The confusion probably arose from the fact that “sugar” is a very very broad term that is often used to describe the whole class or a particular example. Saccharides are all sugars, there are monosaccharides like glucose, fructose, galactose, etc, there are also disaccharides like sucrose (table sugar, which is glucose and fructose linked together), lactose, maltose, etc which are two monosaccharides linked together chemically, then there are oligosaccharides which have usually 3 to 10 (some also count disaccharides as oligo and some go past 10) like raffinose, stachyose, etc, and finally polysaccharides which are quite long chains of sugars (can be quite branched too like a very complex network) like glycogen, starch, cellulose, chitin, etc. These are all sugars.. Some of them we can use in our body and some not (like cellulose). When we eat them (like vegetables, fruits, meat, etc), we break them down into monosaccharides to absorb them into the blood, and then they enter cells and get used up. As our energy carbohydrate storage caches are glycogen, which uses glucose, and as most our cells prefer it, and as the entire metabolic network relies on it (we can make things with glucose and break things down towards glucose, or things can enter glucose metabolic pathways, whether building or breaking, in the middle via special enzymes for them), glucose is by far the most detectable monosaccharide in our plasma (fluid part of blood), the rest do spike a bit after a meal, but are quickly used up or stored, and this is done by liver and some other cells. So when we say blood sugar, we mean level of glucose. We also have a LOT of other uses for sugars, like adding them on proteins and coating cells with them (usually oligo or polysaccharides), we even use sugar derivatives as a kind of signaling system sometimes (adding them transiently to proteins to change their function, like in *O*-GlcNAcylation).