Unit book

• How are monomers joined together?

  A condensation reaction
• How are polymers broken down into their monomers?

  A hydrolysis reaction
• Maltose monosaccharides


  α glucose + α glucose
• Lactose monosaccharides


  α glucose + galactose
• Sucrose monosaccharides


  α glucose + fructose
• Difference between α glucose and β glucose

  α : at C1, the OH group is below the ring

  β : at C1, the OH group is above the ring
• Storage polysaccharides


  • Animals: Glycogen
  • Plants: Starch (Amylose or Amylopectin)
• Structural polysaccharide


  Plants: Cellulose
• Amylose vs Amylopectin

  Amylose:

  • Polymer of glucose joined by α 1-4 glycosidic bonds
  • Forms helix with 6 glucose molecules per turn and about 300 per helix
  • Compact so can be stored in small spaces

  Amylopectin:

  • Polymer of glucoses joined by α 1-4 glycosidic bond & branches of α 1-6 glycosidic bonds
  • Branched rather than helical
  • Easily hydrolysed to provide energy for respiration
• Features & function of starch

  • Insoluble- doesn't affect water potential & osmosis
  • Large + insoluble- Doesn't diffuse out of cells
  • Compact- Lots of glucose can be stored in 1 place
  • Branched (amylopectin)- more enzymes can hydrolyse bonds simultaneously
  • When hydrolysed, forms α glucose- easily transported for respiration
• What is the structure of cellulose?


  β glucose molecules joined by β 1-4 glycosidic bonds in straight, parallel, cross-linked chains; the chains are joined by hydrogen bonds forming microfibrils, forming cellulose fibre
• Glycogen feature and advantage


  1. Insoluble - Does not affect water potential and osmosis
  2. Insoluble - So does not diffuse out of cells
  3. Compact - So lots of glucose can be stored in small places
  4. Highly branched - So many ends can be simultaneously hydrolysed by enzymes
• Amylopectin vs Glycogen

  Amylopectin:

  1. Monomer - α glucose
  2. Bonds - α 1-4 glycosidic, α 1-6 glycosidic
  3. Structure - Branched and helical
  4. Location - Plants

  Glycogen:

  1. Monomer - α glucose
  2. Bonds - α 1-4 glycosidic, α 1-6 glycosidic
  3. Structure - Heavily branched and helical
  4. Location - Animals
• Test for reducing & non-reducing sugars


  1. Add Benedict's solution (deep blue due to Cu2+) to the sample and heat to 95°C
  2. A colour change from blue to green/yellow/orange/red precipitate indicates the presence of a reducing sugar

  Non reducing sugar:

  1. If there is no change, heat a fresh sample with HCl + wait for 5 mins to hydrolyse the glycosidic bonds
  2. Neutralise solution by adding sodium hydrogen carbonate
  3. Add Benedict's solution and heat to 95°C
• Triglyceride


  Glycerol + 3 fatty acid molecules held together by ester bonds
• Roles of lipids


  • Source of energy - when oxidised, produce more than 2x energy as the same mass as a carbohydrate & release water
  • Waterproofing - Insoluble in water so can be used in waterproofing
  • Insulation - fats are slow conductors of heat; when stored beneath the body surface, they retain heat. Also insulate neurons
  • Protection - fat is often stored around delicate organs
• Properties of phospholipids


  • Due to polarity, phospholipids form a hydrophobic barrier between inside & outside the cell
  • Phosphate heads help to keep the structure of the cell
  • Phospholipids allow for the formation of glycolipids at the cell membrane which is important for cell recognition
• How many different amino acids are there?

  ~20
• Amino acids structure

  NH2 (amine group), COOH (carboxyl group, R (variable group)

  
• Fibrous vs globular proteins

  Fibrous:

  • Little to no tertiary structure
  • Long parallel polypeptide chains
  • Cross linkages at intervals- makes stable
  • Long fibres and sheets formed
  • Mostly insoluble
  • Most have a structural role

  e.g. Keratin (hair & outer layer of skin), Collagen (in connective tissue), Silk

  
  

  Globular:

  • Complex tertiary structure
  • Folded into spherical/globular shape
  • Usually insoluble in water
  • Some have a quaternary structure
  • Roles in metabolic reactions

  e.g. Haemoglobin, Enzymes
• Biuret test for protein

  Blue -> deep purple
• Enzyme

  A protein with a tertiary structure, produced in cells. They catalyse reactions in living organisms
• How enzymes work

  Enzymes catalyse a reaction by lowering the activation energy by weakening/bending the bonds in the substrate
• Lock and key vs Induced fit model

  In the lock and key theory, the active site fits the substrate exactly whereas in the induced fit model, the active site changes slightly as the substrate binds to it
• As temperature increases

  The rate of reaction increases
• As temperature increases beyond optimum temperature

  The rate of reaction decreases
• Reason for decreased rate of reaction with increasing temperature beyond optimum

  • Enzyme molecules gain more kinetic energy; tertiary structure bonds vibrate so much that they break
  • Enzyme loses its specific 3D shape, active site changes/denatured and substrate can no longer fit
  • Results in fewer successful collisions
  • Less enzyme/substrate complexes formed
  • Less product formed
• Reason for increased rate of reaction with increasing temperature


  • Enzyme and substrate molecules gain more kinetic energy, results in more successful collisions
  • More enzyme/substrate complexes formed per unit time
  • More product formed

  
• pH affect on enzyme controlled reactions

  A:

  • As pH decreases from optimum and becomes more acidic, r.o.r decreases
  • More H+ ions present disrupt bonds within enzyme active site; no longer complementary & do not join. Fewer enzyme/substrate complexes formed per unit time

  
• Affect of increase pH on enzyme-controlled reactions

  • As pH decreases away from optimum and becomes more alkaline, r.o.r. decreases
  • More OH- ions disrupt bonds with enzyme & active site, active site and substrate no longer join. Fewer enzyme/substrate complexes formed per unit time & less product formed

  
• Affect of increases Enzyme concentration on rate of reaction

  
• Affect of substrate concentration on rate of reaction

  
• Enzyme inhibitors

  • Enzymes can be inhibited, or stopped from working by inhibitors
  • Inhibitors can be used to control the enzyme activity to control the amount of product made or substrate used
  • Disadvantages: many poisons inhibitors respiratory enzymes causing cell death

  
• Affect of competitive inhibitor on rate of reaction

  Slows rate of reaction but will produce the same amount of product

  
• What is a competitive inhibitor & why it is competitive

  • A competitive inhibitor has a similar shape to the substrate which can bind to the active site
  • Which prevents the substrate from binding to the active site and forming an enzyme/substrate complex
• Enzyme-product inhibition

  Too many products forming will give a higher concentration of the inhibitor molecules which then slows the rate of enzyme/substrate complexe formation. This is how cellular enzymes regulated their rate of reaction

  
• DNA

  Deoxyribonucleic acid

  • Polymer of nucleotide monomers
  • Form the instructions for the synthesis of proteins found wishing organisms
  • Contain deoxyribose sugar
• RNA


  Ribonucleic acid

  • Single stranded polynucleotide that exists in 3 forms (mRNA, tRNA, rRNA)
  • Each form plays a part in the synthesised of proteins within cells
• DNA components

  • Phosphate group
  • Deoxyribose sugar
  • Nitrogenous base:

  1. Adenine
  2. Thymine
  3. Guanine
  4. Cytosine

  
• RNA components

  • Phosphate group
  • Ribose sugar
  • Nitrogenous base:

  1. Adenine
  2. Uracil
  3. Guanine
  4. Cytosine