Carbohydrates-sugars Made of C, H,O Carb = Carbon hydrate = water Carbohydrate = carbon + water general formula = C H 2 O ratio of C to H to O ribose C 5 H 10 O 5 glucose C 6 H 12 O 6 sucrose C 12 H 22 O 11 many carbohydrate names end in -ose

More carbohydrate basics Monomer: monosaccharide – one sugar Functions of carbohydrates: Energy for metabolism (glucose) Short term energy storage (glycogen/starch) Structure: plants – cell wall animals – exoskeleton Source of carbon for other molecules Cell surface markers – cell identification

Monosaccharide: Simple Sugars Monosaccharides like glucose are the main source of energy in living things

Disaccharides - 2 sugars 2 monosaccharides linked together by dehydration synthesis - form a glycosidic bond Examples: Sucrose – Table Sugar glucose + fructose Lactose – Milk Sugar glucose + galactose

Polysaccharides-Many Sugars Polysaccharides are polymers composed of large numbers of monosaccharides. - the monosaccharides are joined by dehydration synthesis Used for short term energy storage and structure

Energy Storage Polysaccharides Starch polymer made up of glucose monomers Stores glucose in plants Chloroplast Starch 1  m Starch: a plant polysaccharide

Glycogen Polymer of glucose monomers Is the major storage form of glucose in animals Stored in liver and muscle More highly branched than starch – contains more stored energy Mitochondria Glycogen granules 0.5  m Glycogen: an animal polysaccharide Glycogen

Starch and Glycogen are Easily Broken Apart by Hydrolysis Allows the stored glucose to be easily used

Structural Polysaccharides Cellulose Is a polymer of glucose – connected in a straight unbranched chain Multiple strands of cellulose are held together by hydrogen bonds – makes a rigid structure Is a major component of the tough walls that enclose plant cells

Plant cells 0.5  m Cell walls Cellulose microfibrils in a plant cell wall  Microfibril CH 2 OH OH OHOH O O O CH 2 OH O O OH O CH 2 OH OH O O CH 2 OH O O OHOH O O OHOH O O OH CH 2 OHOH O O CH 2 OH OH O CH 2 OH O O OHCH 2 OH OH  Glucose monomer O O O O O O Parallel cellulose molecules are held together by hydrogen bonds between hydroxyl groups attached to carbon atoms 3 and 6. About 80 cellulose molecules associate to form a microfibril, the main architectural unit of the plant cell wall. A cellulose molecule is an unbranched  glucose polymer. OH O O Cellulose molecules Figure 5.8

Cellulose is difficult to digest Animals can’t break the bonds between the glucose molecules –dietary fiber Animals that eat plants have bacteria in their stomachs that can break the bonds of cellulose- allow their hosts to digest plants Figure 5.9

Chitin, another important structural polysaccharide Is a polymer of a form of glucose with an attached functional group Is found in the exoskeleton of arthropods Figure 5.10 A–C (a) The structure of the chitin monomer. O CH 2 O H OH H H H NH C CH 3 O H H (b) Chitin forms the exoskeleton of arthropods. This cicada is molting, shedding its old exoskeleton and emerging in adult form. (c) Chitin is used to make a strong and flexible surgical thread that decomposes after the wound or incision heals. OH

Other Uses for Carbohydrates Cell surface markers – carbohydrates attached to parts on the cell membrane where they act to identify the cell ABO blood groups are identified by carbohydrates on their surface