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Enzymes - PowerPoint PPT Presentation


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Enzymes. Enzymes are…. Proteins that act as catalysts (accelerate reactions) by creating a new reaction pathway Not specific for what they catalyze and do not permanently change during reactions. Function of Enzymes.

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Presentation Transcript
enzymes are
Enzymes are…
  • Proteins that act as catalysts (accelerate reactions) by creating a new reaction pathway
  • Not specific for what they catalyze and do not permanently change during reactions
function of enzymes
Function of Enzymes
  • Enzymes work by lowering the activation energy (the amount of energy needed to start a reaction).
check for understanding
Check for Understanding

With your partner, label the products, reactants, activation energy, progress of reaction, and free energy on the image below.

Question: Using this image, what is one thing that the enzyme does in this reaction?

enzyme substrate complex

Enzyme

Enzyme-Substrate Complex
  • Substrate is the substance an enzyme acts on and is specific for each enzyme
  • Active site is the region of the enzyme that binds to the substrate

Active Site

Substrate

lock and keys model

S

E

E

E

Enzyme may be used again

Enzyme-substrate complex

P

P

Reaction coordinate

Lock-and-Keys Model
lock and keys model1
Lock-and-Keys Model
  • Keys = Substrates (multiple can bind to each enzyme)
  • Lock = Active Site on the Enzyme
  • As a result of the reaction, the products change shape
  • After the reaction is complete, the substrates are released, freeing up the enzymes to bind with more substrate
check for understanding1
Check for Understanding

With your partner, using what we just discussed, fill in the boxes on the diagram below. Include the name of the part of the enzyme or substrate, and the events that are taking place for the boxes labeled #1-4.

slide9

Substrate matching the enzyme approaches the active site

Product

Product

The substrate bonds to the active site forming the enzyme-substrate complex

The products formed are released and the enzyme is free to bind to a new substrate

The enzyme speeds up the reaction, changing the shape of the substrate

Active Site

Enzyme

induced fit

Active Site

substrate

Enzyme

induced fit

Induced Fit
  • A change in the configuration of an enzyme’s active site (H+ and ionic bonds are involved).
  • Induced by the substrate.
factors that impact enzyme function
Factors that Impact Enzyme Function
  • Temperature
  • pH
  • Substrate Concentration
  • Inhibitors
temperature

Denaturation

Enzyme activity

10

0

20

30

40

50

Temperature / °C

Temperature
  • Enzymes move faster as temperature increases
  • Above optimum temperature, the enzyme denatures – preventing it from binding with the substrate
slide13

Enzyme activity

Trypsin

Pepsin

5

11

9

3

1

7

pH

pH

Optimum pH values

  • Extreme pH will result in denaturation
  • Enzyme structure changes
  • Substrate will no longer fit
  • pH levels different for different enzymes
substrate concentration
Substrate Concentration
  • More substrate causes the substrate to use up the available enzyme faster
  • Once all of the enzyme is bound, the reaction will slow and move at a constant state
competitive inhibitors

Enzyme

Competitive Inhibitors
  • Chemicals that resemble an enzyme’s normal substrate and compete with it for the active site

Substrate

noncompetitive inhibitors

Noncompetitive

Inhibitor

Enzyme

active site

altered

Noncompetitive Inhibitors
  • Chemicals that bind to part of the enzyme (not the active site), resulting in changing the shape of the active site  prevents the substrate from binding

Substrate