Enzymes

• Enzyme

  biological catalyst that increases rate of reaction in a living organisms
• Enzymes

  • They are large proteins made up of long chains of amino acids
  • They can fold into different shapes, each shape being a unique enzyme that catalyzes a particular chemical reaction
  • they are special proteins that act as biological catalysts, and often breaks down (or joins together) molecules
• How enzymes work

  1. Enzyme has an active site with a unique shape complementary to the substrate

  2. Substrate binds to active site

  3. Enzyme catalyzes the reaction, speeding it up

  4. Enzyme is released and can be used again
• Substrate

  The reactant in a chemical reaction
• Products

  The smaller pieces that the substrate is broken into during a reaction
• Enzymes do not change the chemical equilibrium, they only speed up the process
• Lock and key model

  Original model where substrate had to fit perfectly into active site, like a key in a lock
• Induced fit model


  More realistic model where enzyme changes shape slightly to better fit the substrate, like a hand in a rubber glove
• The active site of an enzyme is complementary to the substrate
• Enzymes allow specific reactions to be catalyzed because the substrate must fit the active site
• Monomers-> many small molecules that are bonded together to make a polymer
• Polymers -> large molecule made from many monomers bonded together
• Enzymes are specific
• Enzymes are biological catalysts
• active site-> specific 3D shape on the enzyme that a substrate fits into
• Substrate-> a molecule that fits into an enzymes active site
• Every enzyme has an optimum temperature
• Denature-> when an enzymes active site permanantly changes shape, so it can no longer bind to its substrate
• optimum temperature-> best temperature for the enzyme to work
• Problems that come with increasing the temperature

  1. requires lots of energy
  2. can damage cells
  3. also speeds up non-useful reactions
• synthesis-> molecules go in to make bigger molecule
• 1. Enzyme
  2. + Substrate
  3. enzyme- substrate complex
  4. enzyme+products(break down)
• the active site is complementary to the substrate, so it will only catalyse that specific reaction
• denature-> proteins lose their shape and function, substrate and active site doesnt fit anymore
• Denatured


  Enzyme cannot bind to substrate and catalyze reaction anymore due to active site changing shape
• Optimal temperature


  Temperature at which rate of reaction is highest
• How pH affects enzymes

  1. If pH gets too high or too low, it will lower the rate of reaction

  2. At first, active site just changes a bit so substrate can still fit but less well

  3. Soon, active site changes shape so much that substrate can't fit at all and enzyme becomes denatured
• Optimal pH


  pH at which enzyme works best
• Most enzymes in our body work best at neutral pHs of around 7
• Enzymes that work in the stomach have an optimal pH of around 2 to function in the acidic environment
• Denaturation can be caused by high temperatures or pH levels
• Synthesis-> molecules go through to make a bigger molecule
• Enzymes called carbohydrase convert carbohydrates into simple sugars. Amylase is an example of carbohydrase. Breaks down starch
• Carbohydrate- Starch-> Enzymes (Carbohydrase)-> Glucose molecules (sugar)
• Proteases convert proteins into amino acids
• Protein molecule-> Enzymes (Protease)-> Amino Acids
• Lipase convert lipids into glycerol and fatty acids
• Lipid-> Enzyme (Lipase)-> Glycerol + Fatty acid
• When lipids are broken down, the fatty acids will lower the pH of the solution they are in
• An enzyme is a special type of catalyst that is made by a living organism. We sometimes call them biological catalysts.  Enzymes are large proteins, so made from a long chain of amino acids.