Carbohydrates
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Transcript of Carbohydrates
CarbohydrateCarbohydratess
What are carbohydrates?What are carbohydrates?
Starter:Starter:Write down as many things as you can Write down as many things as you can remember about carbohydrates…remember about carbohydrates…
… … or glucose in particularor glucose in particular
What are they?What are they?
Organic compounds which Organic compounds which comprise of only C, H and Ocomprise of only C, H and O
CarboCarbo--HydrHydr--ateate
Types of CarbohydrateTypes of Carbohydrate
MonosaccharidesMonosaccharides
DisaccharidesDisaccharides
PolysaccharidesPolysaccharides
MonosaccharidesMonosaccharides
Simplest – ‘Single sugars’Simplest – ‘Single sugars’ Same no. of C as O atomsSame no. of C as O atoms
e.g. Glucose is Ce.g. Glucose is C66HH1212OO66
Have the general formula (CHHave the general formula (CH22O)O)nn
Where n is any number between 3 and 7Where n is any number between 3 and 7
White crystalline solidsWhite crystalline solids Dissolve in water to form sweet tasting Dissolve in water to form sweet tasting
solutionssolutions
The structure of glucoseThe structure of glucose
αα-glucose-glucose
You only need to be able to draw α-glucose in its simplified form….
ββ-glucose -glucose
The structure of glucoseThe structure of glucose
• α-glucose and β-glucose are ISOMERS
Monosaccharides form Monosaccharides form DisaccharidesDisaccharides
+
H2O
Maltose
The bond formed is a The bond formed is a glycosidicglycosidic bond bond
A A condensation reaction condensation reaction occurs to join occurs to join the 2 monosaccharidesthe 2 monosaccharides
Monosaccharides form Disaccharides
• α 1-4 glycosidic bonds
Disaccharides hydrolyse to form Disaccharides hydrolyse to form MonosaccharidesMonosaccharides
α-glucose α-glucose
H2O
Disaccharides form Disaccharides form PolysaccharidesPolysaccharides
StarchStarch
StarchStarch The The αα-helical structure of starch makes it -helical structure of starch makes it
good for good for storagestorage (it’s compact!) (it’s compact!) Starch is Starch is insolubleinsoluble due to its structure due to its structure It is therefore the main It is therefore the main plant storageplant storage
sugarsugar
CelluloseCellulose Polymer of Polymer of ββ-glucose-glucose Each monomer is Each monomer is
inverted.inverted. Has consequences forHas consequences for
its properties its properties
CelluloseCellulose Forms chains which run parallel with Forms chains which run parallel with
hydrogen bonds between the chains to hydrogen bonds between the chains to form form microfibrilsmicrofibrils
Microfibrils are strongMicrofibrils are strong Being fibrous, cellulose is structurally Being fibrous, cellulose is structurally
important in important in plant cell wallsplant cell walls
Glucose is not the only Glucose is not the only monosaccharide...monosaccharide...
Fructose:Fructose:
Glucose and fructosecombine to form sucrose (a disaccharide)
Glucose is not the only Glucose is not the only monosaccharide...monosaccharide...
GalactoseGalactose
Galactose Glucose
Glucose and galactose combine to form Lactose
SummarySummary
αα-glucose + -glucose + αα-glucose = -glucose = maltosemaltose The polymer of The polymer of αα-glucose is -glucose is starchstarch The polymer of The polymer of ββ-glucose is -glucose is cellulosecellulose Glucose + fructose = Glucose + fructose = sucrosesucrose Glucose + galactose = Glucose + galactose = lactoselactose
Biochemical Test for Biochemical Test for a Monosaccharidea Monosaccharide
All monosaccharides and All monosaccharides and somesome disaccharides are disaccharides are Reducing SugarsReducing Sugars
i.e. They readily reduce other i.e. They readily reduce other chemicals chemicals when in solutionwhen in solution
We test for reducing sugars using the We test for reducing sugars using the
Benedict’s TestBenedict’s Test
Benedicts TestBenedicts Test
2cm³ of food sample (in liquid form)2cm³ of food sample (in liquid form) 2cm³ of Benedict’s Reagent 2cm³ of Benedict’s Reagent Heat mixture in gentle boiling water bath Heat mixture in gentle boiling water bath
for 5minsfor 5minsConc. of reducing sugarConc. of reducing sugar Colour of solution & Colour of solution &
precipitateprecipitate
NoneNone Stays blueStays blue
Very LowVery Low GreenGreen
LowLow YellowYellow
MediumMedium Brown/orangeBrown/orange
HighHigh Brick redBrick red
In order to detect a reducing sugar, it In order to detect a reducing sugar, it mustmust first be first be hydrolysedhydrolysed into its monosaccharide into its monosaccharide components:components: First test with Benedict’s reagentFirst test with Benedict’s reagent If no colour change:If no colour change:
Add 2cm³ of food sample to 2cm³ of dilute HClAdd 2cm³ of food sample to 2cm³ of dilute HCl Place in gently boiling water bath for 5 minsPlace in gently boiling water bath for 5 mins Slowly add some sodium hydrogen carbonate Slowly add some sodium hydrogen carbonate
solution until neutralized solution until neutralized Re-test using Benedict’s reagentRe-test using Benedict’s reagent