The differences between glucose, sucrose, lactose, fructose, and all of the other “-oses.”
In: Chemistry
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Everything ending in -ose is, of course, a carbohydrate (commonly sugar). The different names are slightly different chemical bonds.
To start with, there are monosaccharides which are the basic blocks that other sugars (polysaccharides) are built out of. The most common ones are glucose (aka dextrose), fructose, and galactose. All three of them have the same chemical formula (~~H6C12O6~~ C6H12O6) but they differ in how they are arranged. [Here is a diagram showing how the atoms are arranged in each.](http://img.sparknotes.com/figures/8/81676752447f7574c97a427f4fb5b546/figure1.gif) Because of the slightly different arrangement of atoms and the slightly different shape the molecule takes, the chemistry is a little different between them. I don’t know enough to explain exactly what the differences in chemistry are. They’re *similar* molecules, though, and *mostly* behave the same, although our body does use them a little differently.
Glucose is what we use for energy. The others have to be converted into glucose to use (*if* our cells have the tools to do so. We can do it with fructose and galactose. Others not so much). Fructose is very useful because it *tastes* sweeter than glucose and sucrose, but because it has to be converted into glucose it doesn’t give as much energy. That means you can make something sweeter with fewer calories. However, because it triggers different behavior in the body in order to use it, it may still be generally less healthy than glucose. Nutrition science is complicated and you should do a *lot* more research before forming an opinion (and remember to use reputable sources with real science).
Also, dextrose is another name for glucose. Sugar molecules are *chiral*, meaning they are “right handed” and “left handed” like your hands. Enzymes that break down dextrose (right handed glucose) can’t break down L-glucose (left handed) because L-glucose doesn’t normally occur in nature. But L-glucose still tastes sweet!
Two monosaccharides make a disaccharide. Sucrose (table sugar) is a disaccharide, made of glucose and fructose. Lactose is a disaccharide made of glucose and galactose. Like the monosaccharides that make them, disaccharides have slightly different chemical properties depending on which monosaccharides they’re made of. Disaccharides can’t be used for energy directly. Instead, they have to be broken apart into their monosaccharides. That takes a special enzyme designed to break apart *that* disaccharide, which is why people become lactose intolerant. Lactose is found exclusively in milk. Once young mammals are weened, they normally never consume it again so they stop producing lactase (the -ase indicating it’s an enzyme; in this case, the enzyme to break down lact*ose*). Humans rarely encounter other disaccharides, except maltose (glucose + glucose) and can’t digest them.
As you may have guessed because it ends in -ose, cellulose is also a carbohydrate, just a really big one. Cellulose is many, many linked glucose molecules in a very long chain. Plants use cellulose to store energy and to build stiff structures like cell walls. Starch is almost the same, just shorter chains of glucose. We can’t digest polysaccharides with more than two sugars very well at all. We just don’t have the enzymes to break them down, and breaking them down takes a very long time. That’s why cows have four stomachs – they chew, then swallow and digest a bit, then regurgitate it back up to chew it some more, then swallow it again, then pass it to the next stomachs in a long path that gives the cellulose plenty of time to break down. Instead, cellulose and starches only get a little broken down and feed bacteria in our guts, which as a side effect makes us farty. The long chains of the cellulose (aka *fiber*) also help bind together our waste so it forms more solid pieces.
EDIT: Just a reminder that [ELI5 is not aimed at literal five-year-olds](https://i.imgur.com/qnnrdGb.png).
Simple sugars: Where the OH, H, and O attach to the carbon frame changes the shape a bit.
Complex sugars: How the simple sugars are attached to each other
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Ok I’ll try to explain with some details but keep it ELI5.
All sugars are sweet and “look” similar if u get really really close to it by a super microscope.
But they are still a bit different.
First there are little simple sugars or “monosaccharides”. Those are:
•Fructose (fruit sugar)
•Galactose
•Glucose
They are different in the way they “look” ie. their structure, which affects their function too! How?
Well like lego parts, you can make bigger sugars called “disaccharide” by joining little glucose to another little glucose or other simple sugars, but only if they fit together based on how they look! Like legos!
These are the disaccharides you can build from monosaccharides:
•Sucrose= Fructose + Glucose (table sugar)
•Lactose= Galactose + Glucose (milk sugar)
•Maltose= Glucose + Glucose
These do (and build) different things in the body and taste different because the way they look is different. Imagine touching a triangle and a cube blindfolded, they feel different right? Same with these sugars! Your body can tell they are different.
tldr super ELI5; they all are similar but different in the way they look ie. their structure. Like lego parts, their different structure makes them able to do (and build) different things and even taste different.
Its all “sugar.” It’s just sugar that is specific to a certain type of food (fructose – fruit, lactose – milk) and each require a specific enzyme to break down (lactose – lactase). This is also a common reason for adult lactose intolerance. Once the body hits a certain age, it slows way the heck down on making the enzymes to break down the milk sugar, meaning that the sugar kinda just sits in your guts until you finally pass it.
One trick I remember from high school biology on how to remember the Monosaccharides and the Disaccharides.
Mo’s Gal has a Fruit Glued to her Rib, Man!
Monosac=. Galactose, Fructose, Glucose, Ribose, Mannose
Disaccharides = Sucrose, Lactose and Maltose. Sue would DI for the Malt she Lacks.
Maltose is made up of two Glucose molecules so….What sound do you make when drinking a malt? Gluc Gluc
I’ve been out of that class for almost 30 years and have never had to use that information practically, but I remember it due to an awesome teacher. He even had a big picture of a girl with an apple on her rib to drive it home.
Thanks Buster Ledford!
Follow up question: which type of sugar(s) do carbs like bread and pasta become when they break down?
Now you’ve got some good quality answers I don’t feel guilty about suggesting that n-ose is for smelling.
Also, the enzyme that digests the sugar is the respective sugar with “-ase” as the suffix.
i.e. Lactase enzyme is needed to digest lactose. Lactose intolerant people lack the lactase enzyme in their body.
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