1. Monosaccharides Flashcards
What are monosaccharide molecules made from?
Carbon, hydrogen and oxygen.
What functional group are monosaccharides?
Polyhydroxy aldehydes or ketones.
What does polyhydroxy mean?
Poly means many, and hydroxy is an −OH group (like those found in alcohols).
Ketones and aldehydes are organic molecules that contain which group?
Carbonyl group (C=O).
Like water, monosaccharines contain twice as many what?
Hydrogens as oxygens.
Aldehyde monosaccharides are known as what?
Aldoses.
Ketone monosaccharides are known as what?
Ketoses, with the prefix keto-.
What is this?
This monosaccharide has six carbon atoms, and the carbonyl group is at the end of the carbon chain, making it an aldehyde. Therefore, this is an aldohexose.
What is this?
The monosaccharide below has five carbon atoms, and the carbonyl group is on the second carbon. Therefore this monosaccharide is a ketone. This is a ketopentose.
As well as their ketone or aldehyde functional group, monosaccharides also have what groups?
Hydroxy groups.
Why are monosaccharides highly soluble in water?
The hydroxy groups of monosaccharides are polar and can form hydrogen bonds with water. Therefore, because of their many hydroxy groups, monosaccharides are highly soluble in water.
Because of these chiral carbons, monosaccharides will have what?
Optical isomers.
Cyclic monosaccharides are often drawn as what?
Hawthorn projections.
What is the most abundant monosaccharide?
Glucose.
What is produced by plants during photosynthesis?
Glucose.
What reaction creates glucose?
Carbon dioxide + water.
The isomer produced by photosynthesis is always what?
D-glucose.
Does the isomer L-glucose occur naturally?
No.
In what form does glucose exist?
Both linear and cyclic form.
The linear form of glucose is an aldehyde, and can therefore be identified with what?
Tollen’s reagent
What are the three glucose isomers that exist in equilibrium in an aqueous solution?
Glucose joins to other monosaccharides to form which disaccharides?
Sucrose and lactose.
Which 3 monosaccharides make up most of the carbohydrates we eat?
Fructose, galactose and glucose.
What is the difference between glucose and fructose?
Fructose usually forms a five-sided ring, whereas glucose forms a six-sided ring—even though they both have six carbon atoms.
In its linear form fructose is a ___, not an ___ like glucose.
Ketone, aldehyde.
Where is fructose found?
Plants, fruit.
In many food sources, fructose exists as part of a disaccharide with glucose.
This forms what?
Sucrose.
Is sucrose sweeter than fructose?
It is sweeter than pure glucose. However, pure fructose is nearly twice as sweet as sucrose.
What is the difference between glucose and galactose?
When do we usually consume galactose?
It is usually consumed as part of the disaccharide lactose which is the main sugar in milk.
Carbohydrates are not the only molecules that taste sweet. What is another?
Aspartame, which is a methyl ester of a dipeptide and used to sweeten foods.
What is a sugar?
A sweet carbohydrate.
