Lecture 10 2 enzymes
Download
1 / 19

Lecture 10-2 Enzymes - PowerPoint PPT Presentation


  • 173 Views
  • Uploaded on

Lecture 10-2 Enzymes. Enzymes. Biological catalysts Lower the activation energy, increase the speed of a reaction (millions of reactions per minute!). How Enzymes Work. Enzymes = large protein molecules that function as biological catalysts.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Lecture 10-2 Enzymes' - cain


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.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Lecture 10 2 enzymes
Lecture 10-2Enzymes


Enzymes
Enzymes

  • Biological catalysts

    • Lower the activation energy, increase the speed of a reaction (millions of reactions per minute!)


How Enzymes Work

  • Enzymes = large protein molecules that function as biological catalysts.

    • Catalyst = chemical that speeds up a reaction without being consumed

    • NOTE: enzyme names end in –ase and are often named after their substrates

      • The enzyme that hydrolyzes sucrose is sucrase

      • Hydrolases, Add water during Hydrolysis reactions


Energy of activation ea
Energy of activation(Ea)

  • There is an energy barrier that must be overcome before a chemical reaction can begin. This is called The energy of activation

  • Enzymes speed up the reaction by lowering the Ea barrier


How Enzymes Work

  • Energy of Activation

    • Enzymes lower the barrier

    • Eg.Mexican jumping bean


How Enzymes Work

The effect of an enzyme on the energy of activation


WITHOUT ENZYME

WITH ENZYME

Activation

energy

required

Less activation

energy required

Reactants

Reactants

Product

Product

PLAY

Animation: Enzymes

Figure 2.20


How Enzymes Work

  • Enzymes

    • Very selective

    • 3D shape that determines its specificity for a substrate

      • Substrate = the substance that the enzyme works on

    • Substrate binds to the enzyme in the active site

      • Pocket or groove on protein surface where binding occurs


Enzyme action
Enzyme action

Three basic steps involves in enzyme action:

1) The enzyme active site binds to the substrate.

2)The enzyme –substrate complex undergoes internal rearrangement that form the product. 3)The enzyme releases the the product of the reaction.



Product (P)e.g., dipeptide

Substrates (S)e.g., amino acids

Energy isabsorbed;bond isformed.

Water isreleased.

Peptidebond

+

H2O

Active site

Enzyme-substratecomplex (E-S)

Enzyme (E)

Enzyme (E)

1

2

Substrates bindat active site.Enzyme changesshape to holdsubstrates inproper position.

Internalrearrangementsleading tocatalysis occur.

3

Product isreleased. Enzymereturns to originalshape and isavailable to catalyzeanother reaction.

Figure 2.21


Substrates (S)e.g., amino acids

+

Active site

Enzyme-substratecomplex (E-S)

Enzyme (E)

1

Substrates bindat active site.Enzyme changesshape to holdsubstrates inproper position.

Figure 2.21, step 1


Substrates (S)e.g., amino acids

Energy isabsorbed;bond isformed.

Water isreleased.

+

H2O

Active site

Enzyme-substratecomplex (E-S)

Enzyme (E)

1

2

Substrates bindat active site.Enzyme changesshape to holdsubstrates inproper position.

Internalrearrangementsleading tocatalysis occur.

Figure 2.21, step 2


Product (P)e.g., dipeptide

Substrates (S)e.g., amino acids

Energy isabsorbed;bond isformed.

Water isreleased.

Peptidebond

+

H2O

Active site

Enzyme-substratecomplex (E-S)

Enzyme (E)

Enzyme (E)

1

2

Substrates bindat active site.Enzyme changesshape to holdsubstrates inproper position.

Internalrearrangementsleading tocatalysis occur.

3

Product isreleased. Enzymereturns to originalshape and isavailable to catalyzeanother reaction.

Figure 2.21, step 3


Characteristics of enzymes
Characteristics of Enzymes

  • Often named for the reaction they catalyze; usually end in -ase (e.g., hydrolases, oxidases)

  • Some enzymes are purely protein.

  • Some functional enzymes (holoenzymes) consist of two parts:

    • Apoenzyme (protein)

    • Cofactor (metal ion) or coenzyme (a vitamin)


Characteristics of Enzymes

  • Cofactors

    • Nonprotein helpers

      • May be inorganic substances

        • Zinc, iron or copper

        • Magnesium is a cofactor essential for proper functioning of chlorophyll

  • Coenzymes

    • Organic helpers

      • Vitamins

        • Vitamin B6 is used to convert one amino acid to another


  • Enzyme activity is affected by its environment

    • Temperature affects molecular motion

      • Enzyme’s optimal temperature is when there is the highest rate of contact between the enzyme and substrate

      • Temperature too high – denaturation

        • Changes the shape and the function of the enzyme

    • Salt concentration

      • Salt interferes with some of the chemical bonds that maintain protein shape

    • pH

      • Same is true for pH outside of the 6-8 range.eg.digestive enzyme produce in pancreas are activated in small intestine.


Characteristics of enzymes1
Characteristics of Enzymes

  • Sometimes enzymes are inactivated immediately after they have performed .eg.

    blood clot formation.



ad