carbohydrates

• monosaccharides are the simple sugar (simplest form of carbohydrate). cant be broken down into simpler sugars by hydrolysis. examples include: alpha and beta glucose, fructose, ribose and galactose
• monosaccharides are classified by the number of carbon atoms they have
• ribose is an example of a pentose sugar. it has 5 carbon atoms. it is a component of a nucleotide
• alpha glucose


  the hydroxyl group on carbon 1 is on the opposite side to carbon 6
• beta glucose


  the hydroxyl group on carbon 1 is on the same side as carbon 6
• glucose

  -soluble (polar- lots of OH hydroxyl groups- more electronegative than H)

  -small molecule

  -readily respired

  -can be joined together to form starch or glycogen
• glucoses properties linked to in real life

  -small molecule- easily enter cells

  -solubility- react with a soluble enzyme, glucose also has to be soluble

  -glucose is hydrophilic so is therefore soluble and can be used in respiration
• the different structures of alpha and beta glucose means they give functional diversity when polymerised or joined together to form a new molecule
• maltose

  2 alpha glucoses joined together through a condensation reaction
• glycosidic bond

  covalent bond between 2 monosaccharides in a disaccharide- made in a condensation reaction
• sucrose

  alpha glucose and fructose
• lactose

  alpha glucose and galactose
• cellobiose

  2 beta glucose
• polysaccharides

  complex carbohydrate chain composed of many monosaccharides joined together formed by glycosidic bonds. examples include: cellulose, starch and glycogen
• starch

  -polymer of alpha glucose

  -plant storage polysaccharide

  -insoluble in water

  -made up of two types of molecule:

  -amylopectin

  -amylose
• amylose

  -insoluble in water (non-polar)

  -carbon 1 bonds to carbon 4 (1,4 glycosidic bond)

  -chain curls in a helix and shape is help by hydrogen bonds

  -unbranched, straight chain molecule
• amylopectin

  -poly-(1,4) alpha-glucose with about 4% (1,6) branches

  -gives it more open molecular structure than amylose

  -branched molecule- increased surface area for enzymes to break it down faster- release energy source faster

  -more ends, can be hydrolysed faster- releases glucose monomers
• iodine test for starch

  blue-black- iodine fits into the helix of the amylase molecule, making it turn blue-black
• glycogen


  -for animals- energy demands are higher than those of a plant

  -found in liver and muscle cells

  -poly (1,4) alpha glucose

  -9% (1,6) branches

  -similar to amylopectin but more branched- breaks down more rapidly- mobilised very quickly to glucose
• cellulose

  -beta glucose

  -cell walls- mechanically strong

  -(1,4) glycocidic

  -straight chains that form stacks

  -microfibril

  -unbranched chains

  -microfibril is very strong

  -lots of microfibril together form fibres
• digesting cellulose

  -dietary fibre

  -cant be digested- dont have specific enzymes for beta
• starch is a good energy storage molecule because it is highly branched, its a compact molecule, insoluble, large and can be hydrolysed to form alpha- glucose
• glycogen is a good energy storage molecule because it is insoluble, compact, highly branched, large and is made of alpha- glucose- animals
• In cellulose, individual beta-glucose monomers join together using glycosidic bonds, whereas cellulose chains are held together by hydrogen bonds.
• cellulose is a strong molecule because it is a long straight unbranched molecule, that can form hydrogen bonds between adjacent chains and can form microfibrils