Enzymes

• All metabolic reactions require enzymes
• What do all cellular reactions include

  Building reactions: Ex. making proteins for amino acids (anabolic)

  Break down reactions: Ex. Digesting foods to extract nutrients (catabolic)
• Catalyst make reactions happen
• How do catalysts make reactions happen 


  Every reaction requires a bit of energy to get going, called activation energy. Enzymes provide this energy
• Each reaction has its own enzymes, in fact they are named after it.

  Enzymes names end in “ase” - exceptions to the end are proteases: pepsin, trypsin, erepsin
• Since there are a lot of reactions in the body, there are a lot of different enzymes.
• Because reactions have to occur slowly to prevent energy release/ uptake from damaging cells (several steps)
• Why are enzymes so specific

  Their shape: the enzyme and the substrate (what the enzyme “works on“) fit together like puzzle pieces (known as the lock + key model)
• The part of the enzyme that is specific to the substrate is the active site. So… different enzymes
• Once the reaction has Occurred, the enzyme is released and is free to catalyze another reaction, Since they can be re-used over and over, we don’t need many enzymes of each kind
• Factors that Effect enzyme activity

  Temperature

  pH

  Enzyme substrate concentration

  Competitive inhibitors

  Co-enzymes + co-factors
• What temperature does the bodies enzymes work best at

  37 (body temp)
• Hypothermia - lower temperatures 


  molecular collisions slow down, therefor enzymes and substrates don’t find each other as much
• High fever - Higher temperatures

  Proteins denature = enzymes and substrates no longer fit

  this is reversible
• At 55 degrees, proteins coagulate

  this is irreversible
• Where on the pH scale do enzymes in the body work best


  7 pH

  exceptions: Stomach enzymes, works best at 2-3 because of stomach acid

  Intestinal enzymes, work best at basic pH (8-9 because sodium biocarbonate)
• Changing the optimal pH results in denature of the enzyme
• More substrate


  Faster reactions until all the enzymes are occupied
• More enzymes 


  faster reactions until there is substrate available
• What are co-enzymes made up of

  Vitamins (Organic)
• What are cofactors made of

  Minerals (inorganic)
• Co-Enzymes and Co-Factors 


  Both help make the enzyme fit better with the substrate
• Competitive Inhibitors

  Chemicals that are similar in shape to an enzymes substrate BUT unlike substrates, they do not leave the enzymes once they bind (stop enzymes)

  Ex. Sulfa drugs (antibiotics) > competitive inhibitors that kill bacteria
• When there is no food, the bacteria is dead

  When there is Food, bacteria is happy
• Mechanisms that controls enzymes 


  Used to turn enzymes on and off
• Metabolic pathways


  Enzymes are found at each step
• What happens when there is too much final product 


  Stop the FIRST enzyme in the pathway until all the product is used up = FEEDBACK INHIBITION
• What happened when there is too much initial substance

  Activate (speed up) the LAST enzyme so that all the other others have to follow suit = PRECURSOR ACTIVATION