Bodies main energy source

CH2O

Only plants synthesise carbohydrates

Starch, Cellulose (polysaccharides)

Lactose, sucrose (dissaccharides)

Glucose, fructose (monosaccharides)

CARBOHYDRATES

(CH2O)n where n=3 to 9

Aldehydes or ketones containing a carbonyl group and at least 2 hydroxyl groups

Hexoses (glucose, galactose, fructose)

MONOSACCHARIDES

Contain 5 carbon atoms

Ribose

PENTOSES

Low molar masses

Sweet

Soluble in water

Crystalline solids

Reducing sugars (aldehyde group oxidised)

PROPERTIES OF MONO AND DI-SACCHARIDES

STRUCTURE OF GLUCOSE

INTERCONVERSION OF Α AND Β GLUCOSE

STRAIGHT CHAIN AND CYCLIC FRUCTOSE

CONDENSATION OF MONOSACCHARIDES

DISACCHARIDE FORMATION

Β-glucose + β-galactose -----> lactose

α-glucose + α-glucose -------> maltose

α-glucose + β-fructose ------> sucrose

Numerous monosaccharide units

Large masses

Not sweet, non-reducing, insoluble

Starch is plant store for glucose

Two forms :

Amylose (water soluble)

Amylopectin (water insoluble)

POLYSACCHARIDES

α-1,4 glycosidic linkages

AMYLOSE

α-1,4 glycosidic linkages as well as α-1,6 glycosidic linkages

AMYLOPECTIN

More highly branched than amylopectin but also has α-1,4 glycosidic linkages as well as α-1,6 glycosidic linkages

GLYCOGEN

Linear

Made up of β-glucose units with all glycosidic linkages in the 1, 4-position

Extensive hydrogen bonding between chains

Strength, rigidity

Insoluble

CELLULOSE

MAJOR FUNCTIONS OF CARBOHYDRATES

Energy Source

Energy Reserve (e.g. glycogen)

Precursor of other Biologically Important Molecules (e.g. anticoagulants, components of nucleic acids)

DIETARY FIBRE

Plant material

Cannot be digested by humans

Parts of fruits, vegetables, grains

May be digested by bacteria in gut

Cellulose

Lignin

Pectin

IMPORTANCE OF HIGH FIBRE DIET

Constipation and DiverticulosisIrritable bowel syndromeObesityCrohn´s DiseaseHaemorrhoids

READING AND QUESTIONS

Please read pages 331 to 334, all about carbohydrates.

Take your own notes.

Make a mind map.

Can you answer the questions in the orange boxes (B.3.1 etc) ?

Now answer questions 9 to 16 on page 359.