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Redox Reactions and Sugars (Trehalose (Circulatory sugar in insects,…
Redox Reactions and Sugars
Carbohydrates
Importance
In Metabolism
Energy storage
Structure
Components of other biological macromolecules
Simple sugars have a backbone of 3 - 7 carbon atoms
Trehalose
Circulatory sugar in insects
Common in fungi
Protects membranes and macromolecules during freezing or dehydration
Reducing sugars
A hydroxyl group (C-OH) can be oxidised to an aldehyde or Ketone
An aldehyde can be oxidised to a carboxylic acid.
Redox reactions involves increase number of oxygen atoms (oxidation) or addition of hydrogen atoms (reduction)
Transfer of electrons from the reducing agent to oxidising agent is the most fundamental process in redox
Oxidising agents become reduced
Reducing agents become oxidised
Transition metals often have many stable electron arrangements and therefore multiple oxidation states
Each half cell reaction has an electrode potential - This is the voltage it generates when it is connected to a standard hydrogen electrode
Strong oxidising agents have high ( more positive) potentials and usually go from left to right
Strong reducing agents have low ( more negative) potentials and usually go from right to left
Hemiacetal formation is readily reversible, opening a sugar's ring and freeing an aldose to act as a reducing agent
Likewise Hemiketals, can revert to the original ketone which can form an aldose under alkaline conditions
Therefore under alkaline conditions, aldoses and ketoses act as reducing sugars
Unlike Hemiacetal and Hemiketals - Acetal and ketal formation is not readily reversible
If the OH group of the hemiacetal or Hemiketal group is converted to an O-R group, then the sugar ceases to be a reducinh sugar. e.g Sucrose
Cellulose
Structural Carbohydrate
Most common macro molecule on earth
Hydrogen bonding between adjacent ribbons leads to formation of ordered bundles of parallel cellulose molecules called microfibrils