disaccharides, too, sugar

Hey, I did warn you that I might return with more carbohydrates - I know I did!
And here I am!
And here they are, too!

This cute couple is known as maltose, but its friends call it 'grain sugar'.
With its glycosidic bond - that's an ether, y'all - between Carbon 1 of the lefthand glucose molecule and Carbon 4 of the righthand glucose molecule, they seem to be holding hands, don't they?
Such sweeties!
(smile)

This couple is a bit more cantankerous - and boy, oh boy, does it show!
Lactose is this couple's name, with them hanging out in dairy products.
You know - just a little 'milk sugar' to make the little ones more apt to feed.
That glycosidic link between Carbon 1 of the galactose (that's the one to your left) and Carbon 4 of the glucose is a bit strained, causing the two halves to go off on a diagonal.
Definitely looks like one is dragging the other to a tuba lesson, doesn't it?
(smile)

Will you have whiskey with your water or sugar with your tea?
What are these crazy questions, Three Dog Night?
And what do they have to do with sucrose anyway?
Sure, we call this one 'table sugar'
and spoon it into our beverages...
Oh, I get it! Sugar!
Such a different structure, with the glucose stacked onto the fructose!
Just like a big baby in a car seat!

Fructose and glucose are similar, but they're not identical twins.
Yes, they are enantiomers, having the same chemical formulas like any isomers do.
Yes, they are hexoses, having six carbons and five alcohol groups.
Yes, they have the same structure from Carbon 3 down to Carbon 6... but their heads definitely differ.
That's because the fructose - in green - exists as a ketose in its Fischer form.
When it forms a ring, it gets...
JAZZ HANDS!!!
Glucose, in red, only has the one hand to wave in the air like it just don't care.
(smile)