Carbohydrates Flashcards
What are carbohydrates made of?
- Carbon
- Oxygen
- Hydrogen
Monomer definition
Smaller units from which larger molecules are made
Monosaccharides
Monosaccharides are the monomers of carbohydrates. Examples include glucose, fructose and galactose
Isomer definition
Same molecular formula
Different arrangement of atoms
Isomers of glucose
- Alpha-glucose
2. Beta-glucose
Differnce between alpha glucose and beta glucose
Diagrams
Condensation reaction
This is where two or more molecules join together. Chemical bond is formed between molecule / molecules, Molecule of water is released per chemical bond formed
Glycosidic bond
Chemical bond formed when two or more monosaccharides join together via a condensation reaction. Molecule of water released per glycosidic bond formed
Disaccharide
Where 2 monosaccharides join together in a condensation reaction. Glycosidic bond formed between the 2 monosaccharides and a molecule of water is released
Disaccharide examples
- Sucrose: Glucose + fructose
- Maltose: a-glucose + a-glucose
- Lactose: glucose + galactose
Hydrolysis
Splitting of a chemical bond via addition of water
Test for reducing sugars
All monosaccharides + some disaccharides are reducing sugars
- Add some benedicts reagent to sample
- Heat sample in boiling hot water bath
- If reducing sugar is present, there will be a coloured precipitate - Blue, green, yellow, orange, brick red (BGYOB)
- The higher the conc of reducing sugar, the further the colour change goes
- This can be used to compare the conc of reducing sugar in different solutions
Test for non-reducing sugars
Non reducing sugars: All polysaccharides + some disaccharides
If reducing sugar not present, a non-reducing sugar may be present
Non-reducing sugar must be hydrolysed into its constituent monosaccharides (reducing sugar), then carry out test as normal for reducing sugar, if reducing sugar present, that means non-reducing sugar present
- Add dilute HCl to sample in boiling hot water bath. If non-reducing sugar is present, the glycosidic bonds between the monosaccharides will be hydrolysed. We now have a reducing sugar
- Neutralise test sample with sodium hydrogen carbonate
- Carry out test as normal for reducing sugar
- If reducing sugar present, coloyred precipiate BGYOB
What is the result if no reducing sugar is present?
Solution remains blue
Polysaccharide Definition
When more than two monosaccharides join together in a condensation reaction. Glycosidic bonds formed between the monosaccharides and a molecule of water is released per glycosidc bond formed