Carbohydrates Flashcards
Contain
Only carbon, hydrogen, oxygen
General formula
Cx (H2O) y
3 groups
Monosaccharides - single sugars eg galactose, fructose, glucose
Disaccharides - two sugars eg maltose, sucrose, lactose
Polysaccharides - many sugars eg starch, cellulose, glycogen
Condensation reaction
Two monosaccharides join to from a disaccharides, water is also produced and a glycosidic bond forms
Many monosaccharides join in many condensation reactions to form a polysaccharide
Most common monosaccharide
a Glucose - C6H12O6
Isomer
Molecule with the same molecular formulae but a different arrangement of atoms
Optical isomerism
When the bonds in the molecules can rotate in space to give a different form of the molecule (glucose to B glucose)
B glucose - the hydroxyl group rotates 180 around carbon 1
Fructose and galactose formulae + structure
C6H12O6 - makes it a structural isomer of A and B glucose (different arrangement of atoms, same molecular formulae)
Hexose sugars - 6 carbon atoms
Monosaccharides use
Make ATP - respiration
Formation of other carbohydrates
Formation of other molecules (DNA & RNA)
Properties of monosaccharides
Small, can move across membranes with channel or transport proteins
Soluble in water, easily transportable and diffuse around living organisms to be used as a respiratory substrate
Lower water potential
Reducing sugars
Test for reducing sugars
Add Benedicts reagent, heat
Present - red/brown/orange/green
Absent - blue
Reducing sugars , quantitative
Use standard solution, a colorimeter and calibration curve
Reducing properties come from
The aldehyde or ketone group within the molecule
Disaccharides
Maltose, sucrose, lactose
Bond formed when 2 monosaccharides join by a condensation reaction with a glycosidic bond
Maltose + formulae
Disaccharides formed by condensation of A glucose & A glucose
C12H22O11 as there are 2x glucose and - water since it is a condensation reaction
Sucrose + formulae
disaccharides formed by condensation of A glucose & fructose
C12H22O11 as there are 2x glucose and - water since it is a condensation reaction