Sem título

Slide 1

• Carbohydrates
• -are hydrophilic organic molecules with the general formula
• (CH2O)n. n=number of carbons.
• - In the sugar glucose for example n=6 i.e. Glucose formula
• =C6H12O6
• - the names of most carbohydrates include the words
• saccharide or ose both of which means sugar or sweet
• The most well known carbohydrates are sugars, starch and
• cellulose
• Carbohydrates structure: they can be polyhydroxy aldehydes
• or ketones or substances that can exist in a bonded form or as an open ring or
• chain form as well
• Carbohydrate classification:
• carbohydrates are classified according to the number of units monosaccharides
• (1 unit), disaccharides (2 units), oligosaccharides (>2-10 units),
• polysaccharides (>10 units). 2) Functional groups represent aldehyde (-CHO),
• ketone (-CO) 3) number of carbons within each unit (tri, tetra) 4) open ring or
• chain form

Slide 2

• Monosaccharides: the simplest
• carbohydrates also called simple sugars. They cannot be hydrolysed into smaller
• units. Two groups aldoses (aldehyde group) e.g. Glucose, ketoses (ketone group)
• e.g. fructose, contain two or more hydroxyl (-OH) groups making them extremely
• soluble in water. Structural isomers: glucose and fructose have the same
• molecular formula C6H12O6 but have a different structural formula. Ring structures:
• all monosaccharides with at least 5 carbons e.g. glucose exist predominately in
• the cyclic forms rather than open chained forms. Most form six membered rings
• called pyranose rings, some five membered form rings called furanose rings.
• They act like alcohols , aldehydes and ketones, reducing agents can reduce the
• aldehyde or ketone carbonyl groups to an alcohol.
• Disaccharides: Carbohydrates
• that are composed of two monosaccharide units joined together e.g. sucrose,
• maltose, lactose. Formation of disaccharides occur when 2 disaccharides undergo
• a condensation reaction to produce a disaccharide with the release of water.
• Glycosidic link: the C-O-C bond that joins two monosaccharides to produce a
• disaccharide
• Polysaccharides: include
• complex carbohydrates such as starch, glycogen, cellulose, agar, pectin, gum
• Arabic, heparin and chitin. They can be hydrolysed into smaller units. Starch:
• storage polysaccharide for plants, a polymer of glucose monomers, made up of
• two fractions amylose and amylopectin. Amylose: soluble in water turns blue
• with iodine. Amylopectin: insoluble in water no colour change with iodine.
• Glycogen: reverse carbohydrate for animals found mainly in the muscle and
• liver. Cellulose: provides structural support in plant cell walls, cellulose
• fibres consist of bundles of parallel polysaccharide chains held together by H
• bonding thus providing mechanical strength, insoluble in water, no colour
• change with iodine

Slide 3