AP Notes, Outlines, Study Guides, Vocabulary, Practice Exams and more!

Enzymes

enzymes - proteins that control most reactions in cells

  • biocatalysts - speeds up metabolic reactions to biologically useful rates
  • lowers activation energy needed for reaction to start
  • substrate - reacting molecules that binds to the enzyme to make enzyme-substrate complex
    • active site - where substrate attaches to the enzyme
  • provides energy of activation to form the transition state (making substrate more reactive)
  • completes reaction when product formed, enzyme goes back to original shape
  • structure/shape determines enzyme’s function
  • denaturation - structural change to enzyme, can destroy its effectiveness
  • optimal conditions - the environmental conditions under which the enzyme works the best
  • phosphate-carrying molecules like ATP turn enzymes on/off through phosphorylation

effect of temperature on enzyme activity

  • heat usually increases rate of most chemical reactions (puts energy into the system)
  • extreme temperatures may denature enzymes

catechol oxidase - plant enzyme converting catechol to benzoquinone

  • benzoquinone responsible for brown color in bruised fruit
  • catechol >> catechol oxidase >> benzoquinone
  • no reaction if either catechol oxidase or catechol missing
  • low temperatures >> slower reaction
  • moderately high temperatures (about 40° C) >> fast reaction
  • extremely high temperatures (about 80° C) >> denatured enzyme, no reaction

effect of pH on enzyme activity

  • H+ and OH- groups from acids/bases react w/ side groups of enzyme molecules
  • lower pH >> more H+ ions
  • higher pH >> more OH- ions
  • can change enzyme shape enough to change active site

catalase - enzyme in plants/animals, speeds up hydrogen peroxide breakdown

  • 2 H2O2>> catalase >> 2 H2O + O2
  • no reaction if either catalase or hydrogen peroxide missing
  • works best in neutral pH
  • adding acid/base/buffer can change the pH

effect of inhibitors on enzyme activity  

  • competitive inhibition - inhibitors that compete for the same active site as a substrate
    • makes enzyme unavailable for substrate
  • can also bond to allosteric site and shut off enzyme
Subject: 
Biology
Subject X2: 
Biology

Need Help?

We hope your visit has been a productive one. If you're having any problems, or would like to give some feedback, we'd love to hear from you.

For general help, questions, and suggestions, try our dedicated support forums.

If you need to contact the Course-Notes.Org web experience team, please use our contact form.

Need Notes?

While we strive to provide the most comprehensive notes for as many high school textbooks as possible, there are certainly going to be some that we miss. Drop us a note and let us know which textbooks you need. Be sure to include which edition of the textbook you are using! If we see enough demand, we'll do whatever we can to get those notes up on the site for you!