Carbohydrates
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why do large molecules often contain carbon
carbon atoms readily form bonds with each other that form a backbone that other atoms can be attached
Monosaccharides
Simplest form of sugar and are water soluble
Reducing sugars
Can donate electrons to a molecule (benedict’s reagent)
What 3 elements are found in monosaccharides
carbon, hydrogen, oxygen
What are the 3 monosaccharides
Glucose, galactose, fructose
What are the isomers of glucose
-alpha -beta
Glycosidic bond
the bond that forms between two monosaccharides during condensation to form a disaccharide
Maltose
glucose + glucose
Lactose
Galactose + glucose
Sucrose
fructose + glucose
Disaccharide
form when 2 monosaccharides chemically react together
polysaccharides
formed by the condensation of many glucose units
Why are polysaccharides good for storage
they are large molecules that are insoluble
Test for starch-iodine
-add sample to spotting tile -add drops of iodine and stir -starch is indicated by a colour change from orange to blue-black
Test for reducing sugars
Benedicts
Why does benedict’s reagent turn red when heated with a reducing sugar
sugar donated electrons that reduce blue copper 2 sulfate to orange copper 1 oxide
Benedict’s test
• grind up food and filter solids • Add solution to boiling tube and add benedict’s solution • heat for 5 minutes 4.If it remains blue there are no reducing sugars present if it turns red there are
How do you test for a non-reducing sugar
-Add sample and benedicts to water bath for 5 minutes -if no colour change then a reducing sugar is not present -Heat another sample with acid and neutralise; - Heat with Benedict’s (solution); -Red precipitate/colour;
Starch
made up of chains of alpha glucose monosaccharides linked by glycosidic bonds that are formed by condensation reactions
What type of glucose is starch and glycogen made from ?
Alpha glucose
What type of glucose is cellulose made from?
Beta glucose
Structure of starch
Made up of amylose which is unbranched, coiled and compact. And amylopectin which is branched so enzymes can work simultaneously.
Structure of glycogen
Very similar structure to starch but has shorter chains and is more highly branched
Structure of Cellulose
-Long, straight unbranched chains of beta glucose joined by glycosidic bonds -Microfibrils are strong threads that made of long cellulose chains that run parallel joined by hydrogen bonds (cross-linkage)