L18: Biological Reactions-Carbohydrates Flashcards
2 key functional groups
Aldoses: Contain aldehyde (-CHO)
Ketoses: Contain ketone (C=O)
Describe the cyclisation process in glucose
1) OH group on C5 attacks carbonyl carbon (C1), forming new C-O bond
2) Creates 6-membered ring
3) New chiral center introduced at C1
4) 2 anomers form: alpha-anomer & beta-anomer
What are anomers?
Type of epimer that differ between each other at the anomeric carbon
Which molecule can mutarotation occur in, and why?
Water
Because alpha & beta can switch back and forth
What are the 2 types of anomers?
Alpha & Beta Anomer
alpha: always down
beta: up
What are 2 anomers that can be created in fructose?
1) alpha-D-fructofuranose
2) beta-D-fructofuranose
How are anomers formed in fructose?
1) Fructose has ketone group at C2
2) C2 ketone reacts with OH group at C5 forming 5-membered furanose ring
3) Makes new anomeric carbonat C2
What are disaccharides?
2 monosaccharides joined by a glycosidic bond
Describe isomerisation in sugar chemistry in the test tube
1) base-catalysed isomerisation of sugars via an enediol intermediate
2) can produce D-mannose from D-glucose at C2 inversion
What is an enediol intermediate?
Allow D-glucose to convert to another sugar
What can aldoses be oxidised to?
Easily oxidised to acids
What can ketoses be oxidised to ?
Oxidised via isomerisation to aldoses
Which sugars are reducing?
Glucose, fructose, galactose
Which sugars are non-reducing?
Sucrose
Why are some sugars known as reducing?
Can be detected by simple chemical reactions that reduce metal to its elemental form e.g silver
What is the ‘silver mirror’ experiment about?
Oxidation of sugar by a metal ion in solution
What does enzymes function as?
1) Acids/bases- protonating/deprotonatnig substrates
2) Stabilise high-energy intermediates via non-covalent interactoins
