headstart biology AS

  • Created by: charlie
  • Created on: 01-09-13 16:14


  • made from: 20 diff amino acids (C, H2, O2, N2, some S) 
  • held by strong covalent bonds
  • order of AA ---> determines structure of P ---> determines how it works 
  • each protein has original shape 

primary structure 

  • order in which AA are arranged in a chain 

secondary structure 

  • chains coil/ fold to pleats ---> held by weak forces of chem attraction (H2 bonds)

tertiary structure 

  • coil chain folded ---> ball ---> weak chem. bonds (H2) + strong (S bridges) 
  • protein roughly spherical = globular protein (e.g. enzymes) 
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  • made from: C, H2, O2 ... e.g. sugars, starch, cellulose (small, water-soluble, sweet molecules)
  • monosaccharides:  single units from which all othe carbs built ---> glucose + fructose 

  • disaccharides: 2 MS joined by chem. reaction + molecule of water (so condensation reaction)

starch is a polysaccharide

  • polymers- large molecules made from monomers which are monosaccharide 
  • made from 2 PS= amylose + amylopectin (polmers of glucose)
  • insoluble starch ---> good for storing glucose + ONLY found in plant cells 

cellulose is a PS

  • polymer of glucose (like starch but bonding is diff.)
  • cellulose molecules long + straight ---> several lie side by side---> form microfibrils (strengthens plant cell wall)
  • molecules held by weak H2 bonds 
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oils + fats made from: C, H2, O2 


  •  group of lipids that make up plant oils+animal fats 
  • made from glycerole molecule + 3 fatty acids 

a fatty acid= long chain of carbons, acid group at end(-COOH), double bond to O2, H2 molecules

  • saturated fatty acid= every carbon joined by single bond
  • unsaturated= one double bond or polyunsaturated= more than one double bond 

phospholipids= special type of lipid 

  • glycerole molecule, 2 fatty acids, phosphate group 
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  • speed up biochemical reactions acting as biological catalysts inc. ROR
  • sum of reactions = metabolism         single chain reaction= metabolic pathway 

activation energy 

  • every reaction requires e input= activation energy 
  • reaction needing high activation energy cant start at low temps
  • enzymes reduce acitvation energy 

enzymes are proteins 

  • globular proteins + order of amino acids determine structure + how it works 
  • break down or build molecules 
  • e.g digestive enzymes- help break down food to smaller molecules 
  • e.g DNA polymerase- builds molecules in DNA replication 
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enzymes part 2

active site 

  • substrate= substance thats acted upon enzyme 
  • active site= region of surface- substrate attaches + where catalyed reaction takes place 
  • soon as enzyme-substrate complex formed ---> products of rection released + start again

enzymes are specific 

  • catalyses one specific chemical reaction + substrate must be correct shapeto active site 
  • only one substrate will fit so only one chem. reaction 
  • change in active site affects enzyme performance 


  • inc. reaction faster as more e for enzyme 
  • high temp. vibrate rapidly + break weak bonds holding tertiary structure- shape changes + substrate no longer fits = denatured 

pH ---> acids+alkalis can denature enzymes ---> hydrogen ions  (H+) in acids + hydroxyl ions (OH-)in alakalis disrupt weak bonds + change active site

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