carbohydrates

• amylase breaks down starch into maltose in a hydrolysis reaction
• maltase breaks down maltose into glucose with hydrolysis
• sucrase breaks down sucrose into glucose and fructose using a hydrolysis reaction
• monosaccharides are monomers which larger carbohydrates are made frkm
• a condensation reaction between two monosaccharides forms a glycosidic bond
• disaccharides are formed by the condensation of two monosaccharides
• maltose is a disaccharide formed from the condensation of two glucose molecules
• sucrose is a disaccharide formed by a condensation reaction of a glucose and fructose molecule
• lactose is a disaccharide formed by the condensation of a glucose and a galactose molecule
• glucose have 2 isomers, alpha and beta
• alpha glucose OH BELOW

  
• beta glucose OH ABOVE

  
• polysaccharides are formed from the condensation of many glucose units
• glycogen and starch (polysaccharide) are formed by the condensation of a alpha glucose
• cellulose (polysaccharide) is formed by the condensation of beta glucose
• monosaccharides

  • simplest sugars
  • white crystalline solids
  • disolve in water to form sweet tasting solutions
  • ex, glucose, fructose, galactose
• condensation reaction forms a glycosidic bond between two monosaccharides
• GLUCOSE+FRUCTOSE=SUCROSE

  enzyme used- sucrase
• GLUCOSE+GALACTOSE=LACTOSE

  enzyme used- lactase
• GLUCOSE+GLUCOSE=MALTOSE

  enzyme used- maltase
• condensation is making the monomers join to form longer polymers
• hydrolysis breaks polymers down into monomers using a water molecule to break the bond
• Sucrose is not a reducing sugar
• all monosaccharides and some disaccharides (maltose) are reducing sugars

  • they readily reduce other chemicals when in solution
• testing for reducing sugars using BENEDICTS SOLUTION

  • heat sample with benedict’s
  • if sample stays blue no reducing sugar present
  • if sample forms green, yellow, orange, brick red precipitate there is a reducing sugar present
• non reducing sugars are some disaccharides like sucrose

  • non reducing sugars need to be hydrolysed
  • (by boiling with HCL)
  • into their constituent monosaccharides
  • reducing sugars test (benedict’s) is then preformed
• Test for NON REDUCING SUGARS

  • heat sample with benedicts reagent
  • if sample forms green- brick red, reducing sugar is present
  • if sample stays blue, no reducing sugar present
  • so boil a new sample with dilute HCL, then neutralise sample by adding sodium hydrogen carbonate (alkali)
  • heat sample with benedicts reagent
  • if sample stays blue NO NON REDUCING SUGAR PRESENT❌
  • if sample forms green,yellow,orange,brick red precipitate NON REDUCING SUGAR IS PRESENT ✅
• a polysaccharide is formed when more than two monosaccharides are joined together by condensation reactions using glycosidic bonds
• polysaccharide can be broken down into their constituent monosaccharides by HYDROLYSIS reactions
• CELLULOSE

  • made of long straight unbranched chains of BETA glucose
  • each chain linked together by lots of HYDROGEN bonds which form strong fibres called MICROFIBRILS
  • MICROFIBRILS ARE ARRANGED PARALLEL GROUPS CALLED FIBRES
  • strong fibres mean cellulose provide structural support for the cells
• Beta glucose in cellulose is held together by glycosidic bond
• function of a cellulose cell wall

  • provides rigidity to the plant cell
  • prevents plant cell bursting (LYSIS) when water enters by osmosis
• Starch is formed by maltose (alpha)
• Plant cells use glucose in respiration, however glucose cannot be stored as it is soluble and has an OSMOTIC effect on the cell. plants therefore store glucose in the form of starch as it is INSOLUBLE
• Structure of Starch

  • starch is mix of two polysaccharides
  • amylose and amylopectin
  • both are made from king chains of alpha glucose linked together with GLYCOSIDIC bonds formed burning condensation reactions
• Structure of AMYLOPECTIN

  • short term store
  • long and branched
  • side branches allow the enzymes to hydrolyse the glycosidic bonds easily
  • alpha glucose is released very quickly
• structure of AMYLOSE

  • long term store
  • long and unbranched
  • compact
  • coiled structure held in place by hydrogen bonds
  • good for storage as you can fit more in a small space
• AMYLOSE

  • a long unbranched chain of ALPHA glucose molecules coiled into a spiral, held together by hydrogen bonds (it has glycosidic bonds inbetween the glucose)
  • bond between each alpha glucose is 1,4
• AMYLOPECTIN

  • made up of branched chains on alpha glucose molecules
  • a 1,6 linkage from branches
  • a 1,4 linkage between alpha glucoses
• starch is good energy store as

  • insoluble (doesn’t dissolve and affect the osmotic balance of cells, preventing water from entering cells and causing them to swell)
  • compact structure ( coiled and branched amylopectin) large amounts of energy can be stored in a small place