Carbohydrates

CarbohydratesCarbohydrates are made from CARBON, HYDROGEN and OXYGEN

Plant cell walls depend on the structural role of some carbohydrates

They STORE ENERGY in plants and animals

MONOSACCHARIDES

CARBOHYDRATES

POLYSACCHARIDESDISACCHARIDES

(CH2O)n

MonosaccharidesMonosaccharides are small organic molecules used as bulding blocks for more complex carbohydrates. Click each of the blue boxes to work through the slide.

General FormulaWhat does the ‘n’

stand for?

Number of Carbon atoms

So, when n=3TRIOSE, e.g. glyceraldehyde -

In metabolic reactions

When n=5 When n=6

HEXOSE, e.g. glucose -

main source of energy

PENTOSE, e.g. ribose –

formation of nucleic acid

Isomerism in Glucose C6H12O6

CH2OH

CH2OH

Alpha-glucose

beta-glucose

Show structural change

Oxygen

Hydrogen

Carbon

Hydroxide (OH)

GLUCOSE

MALTOSESUCROSE

GLUCOSE

GLUCOSE

Disaccharides

A disaccharide can be made from two of the same

monosaccharide molecule or from two different ones.

Disaccharides form when two monosaccharide units join forming a

glycosidic bond, by a condensation reaction.

The combination of monosaccharides determines which disaccharide is formed.

MONOSACCHARIDES DISACCHARIDE

FRUCTOSEGALACTOSE

WATERWATERWATER

LACTOSE

GLUCOSE

OOHOH

Forming Disaccharides

C C

C

C O

C

H

OH

OHOH

OH

HH

CH2OH

H

H

CH2OH

C C

C

C O

C

H

OH

OHOH

OH

HH

CH2OH

H

H

C C

C

C O

C

H

OH

OH

OH

HH

CH2OH

H

H

C C

C

C O

C

H

OH

OH

OH

HH

CH2OH

H

H O

H H

PolysaccharidesPolysaccharides are large complex molecules known as

POLYMERS.

Monomers are the individual monosaccharides which join to form the polysaccharide.

Polymerisation is the process of bonding many MONOMERS by condensation reactions to form one large molecule.

Po

lys

acc

har

ide

s Monomer Glycosidic bond

GLYCOGEN α Glucose 1-4 and 1-6

STARCH α Glucose 1-4

CELLULOSE β Glucose 1-4 and 1-6

What is polymerisation?

What is a monomer?

OOHOH

Forming polysaccharides

C C

C

C O

C

H

OH

OH

HH

CH2OH

H

H

C C

C

C O

C

H

OH

OH

OH

HH

CH2OH

H

H

O

H H

In this example, 3 condensation reactions have produced 3 water molecules to produce the polysaccharide.

O

H H

C C

C

C O

C

H

OH

OH

OH

HH

CH2OH

H

H

C C

C

C O

C

H

OH

OH

HH

CH2OH

H

H

OHOH OHOH

Glucose

O

O

H H

O

A HYDROLYSIS reaction (addition of water) reverses the reaction and splits the polysaccharide releasing 3 monosaccharide molecules.

You can give this question a go, in order to prove your understanding: