1 / 16

Unit 2.2 Enzymes: a Special Class of Proteins

Unit 2.2 Enzymes: a Special Class of Proteins. Vocabulary:. Activation Energy : the amount of energy needed to get a reaction started. Enzyme : a special class of proteins that catalyze reactions in living organisms.

zenda
Download Presentation

Unit 2.2 Enzymes: a Special Class of Proteins

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Unit 2.2 Enzymes: a Special Class of Proteins

  2. Vocabulary: Activation Energy: the amount of energy needed to get a reaction started. Enzyme: a special class of proteins that catalyze reactions in living organisms. Catalyst: a substance that increases the rate of a reaction without being consumed as part of the reaction. Active site: part of an enzyme where a rxn occurs. Substrate: molecule(s) on which an enzyme acts. Denature: to deform or change the shape of, thereby rendering the enzyme inactive.

  3. I. Reactions: (abbreviated as “rxn”) catalyst • General reaction equation: reactant(s) product(s) • Reactant(s): • Reactants are the substance(s) that are “doing the reacting”; usually written on the left side of the equation/arrow. • Product(s): • Products are the substance(s) “produced” as part of the reaction; usually written on the right side of the equation/arrow. • Catalyst: • Any substance that speeds up a rxn without being consumed as part of the rxn. • If a catalyst is used, it is written above the arrow to show that it is not consumed as part of the reaction.

  4. Energy of Reactions: • Exergonic/Exothermic • exo = out, off; erg- = energy; therm = heat • Release energy • **Starting reactants have more energy than ending products** • Like a ball rolling downhill • Endergonic/ Endothermic • endo = in • Require/take in energy • **Starting reactants have less energy than ending products** • Like pushing a ball uphill

  5. Which rxn is exergonic? Which is endergonic?

  6. Activation Energy: amount of energy needed to start a reaction • Even if reaction is exergonic, may need energy to start. • Catalysts reduce activation energy: • Make reactions happen much faster, but are not consumed as part of the reaction, so can be reused again and again. • Enzymes are biological catalysts.

  7. “A” represents activation energy needed for rxn. • “B” represents activation energy needed when a catalyst is available (same reaction, less activation energy). • Is this rxnendergonic or exergonic?

  8. II. Enzymes • An enzyme is a protein whose function is to catalyze chemical reactions • Enzyme names end in “-ase” • Enzymes can be named for substrate on which they act: • Ex: lactase breaks down lactose; peroxidase breaks down peroxide • Or the type of reaction that the enzyme catalyzes: • Ex: DNA polymerase forms DNA polymers

  9. Structure of enzymes: • Active site has specific fit for substrate • Like a “lock-and-key” • Substrate: molecule(s) that an enzyme breaks apart or puts together • Active site: area of enzyme that interacts with substrate

  10. Enzymes reduce activation energy in two ways: • Holding substrate in correct orientation to make joining, bonding easier • Or may “twist” substrate to make breaking bonds easier

  11. IV. Speed of Reaction: • Three factors can change how fast a reaction occurs: • Amount of substrate • More substrate = faster rxn, until enzyme is working as fast as possible • Less substrate = slower rxn • Amount of enzyme • More enzyme = more rxns • Less enzyme = fewer rxns

  12. Temperature • As temp. decreases, then rxn slows down - why? • lower temp = less energy, so molecules have less energy, move more slowly • As temp. increases, then rxn speeds up – why? • higher temp = more energy, so molecules have more energy, move more quickly • But if temp. is too high, then “denatures” enzyme • Denature = deformed, changes shape of active site so substrate no longer fits

  13. V. Factors that affect enzyme function • Enzymes need correct conditions to keep correct shape: • Temperature: depends on organism • ~95-101°F for warm-blooded animals • pH: depends on the enzyme • Stomach enzymes need low pH (~2) • Intestinal enzymes need high pH (~8) • Amount of salt: depends on cell chemistry • Most need low salts (0.1M) • But halophilic algae/bacteria can stand higher amounts

  14. If conditions are not correct, then enzyme can deform - denature. • High temperatures: break hydrogen bonds that hold polypeptide chains together • Wrong pH: can change charge (+/-) of amino acids, deforms them • Too much salt: can change ionic interactions of amino acids, cause them to deform

  15. Warm-up answers for this unit:

  16. Warm-up answers for this unit:

More Related