Carbohydrates Flashcards
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)
What bonds cellulose together
Hydrogen bonds
What two molecules is starch made from ?
Amylose and amylopectin
What makes starch suited to its role as an energy store
- it’s insoluble and therefore doesn’t affect water potential
-it’s compact so a lot of it can be stored in a small space
-it’s large and insoluble so doesn’t diffuse out of cells
What makes glycogen suited to its role as an energy store
-it’s insoluble and therefore doesn’t tend to draw water into cells
-it doesn’t diffuse out of cells
-it’s compact so lot can be stored in a small space
-highly branched so more enzymes can work simultaneously
What is starch used for
energy store in plant
What is glycogen used for
energy store in animals
What is cellulose used for
Component of plant cell walls and provides rigidity to the wall, prevents the cell from bursting
What makes cellulose suited to its role as an energy store
-made of beta glucose and so form long straight, unbranched chains
-cellulose molecular chains run parallel to each other and are cross linked by hydrogen bonds which add collective strength
