Carbohydrates•

Carbohydrates• The most common building material on Earth

• Made of Carbon Hydrogen and Oxygen(Most have the ratio 1:2:1 for C:H:O)

• Used as energy source, building material & cell surface markers

• There are three major types

1.Monosaccharides (simple sugars)made of single carbon chain with hydroxyl

attacheddry state is linear

wet state (dissolved) is ring

Monosaccharidesdistinguished by carbonyl group ie aldehyde – aldose sugar, ketone – ketose

sugar

MonosaccharidesIsomer – a molecule with the same chemical

formula but with different arrangement of atoms (pg31 Fig 8(b))

α Glucose β Glucose

2.Dissaccharides (Oligiosaccharides)

made up of 2 sugars (monosaccharides)subunits are attached by a linkage called

GLYCOSIDIC LINKAGE which is made by condensation reaction (pg. 31 Fig 8 a&b)

Why do glycosidic linkages have numbers in them?Remember when we said that functional

groups are more reactive and therefore more important than the C-H bonds?

We number the carbons starting closest to the functional group

Two glucose molecules have come together to form a maltose molecule. What is the linkage called?

1-4 glycosidic linkage

Explain why this is a 1-2 glycosidic linkage.

3. Polysaccharides (complexcarbohydrates) made of 100’s and 1000’s of

monosaccharidescan be straight chained or branchedserve 2 functions –

energy storage (starch, glycogen)structural support (cellulose, chitin)

PolysaccharidesStarch – (How plants store energy)

–there are 2 typesAmylose – unbranched α glucose

polymer with an α 1-4 glycosidic linkage

Amylopectin – branched α glucose polymer with an α 1-4 glycosidic linkage α 1-6 glycosidic linkages cause the polymer

to twist into coils making it insoluble in water

Polysaccharides - starch

amylopectin

PolysaccharidesB. Glycogen One way animals store energy (in muscle and

liver cells)1-4 glycosidic linkagessimilar to amylopectin but more branchesGlycogen in liver

cellsGlycogen

PolysaccharidesCellulose – major polysaccharide of

plants straight chain polymer of β glucose held by alternating alpha and beta 1-4 glycosidic

linkage (which makes it indigestible) not coiled so form tight bundles called microfibrils