proteins making chemical reactions possible. energy and chemical reactions most chemical reactions...
TRANSCRIPT
Energy and chemical reactionsMost chemical reactions require energy to
begin - the energy required to start a chemical
reaction is called activation energy.
What are enzymes?Enzymes are proteins which reduce
activation energy allowing chemical reactions to occur in living things
Enzymes Act as Biological CatalystsCatalysts are inorganic molecules that speed up
chemical reactions - catalysts remain unchanged by the reaction that
they speed up. -one molecule of catalyst can catalyze (start) many chemical reactionsEnzymes speed up reactions in living things
-enzymes are not changed by the reaction they speed up
- one molecule of enzyme can catalyze (start) many reactions
Active SiteEnzymes have an area called an active site. - the active site is where the chemical
reaction occurs
The Shape of the Enzyme Determines FunctionThe active site of the enzyme fits with only
one type of molecule known as the substrate.Substrate is the molecule that the enzyme
acts on.The fact that the active site can only accept
one type of substrate is known as enzyme specificity
Enzyme ReactionsWritten as : Enzyme + Substrate ES Enzyme + Product - ES refers to the enzyme substrate complex, the time
when the substrate joins with the active site.
Example
Catalase + 2H2O2 ES Catalase + 2H2O + O2
enzyme substrate enzyme enzyme product product substrate complex
Lock & Key ModelSubstrate fits into the active site like a key
into a lockThe enzyme puts stress on the bond which reduces the amount of energy needed to break apart the substrateThe products of the reaction leave and make the enzyme available for more substrate
Induced Fit ModelSubstrate doesn’t quite
fit into the active siteSubstrate causes
(induces) the enzyme to
change shape – allows the substrate to fit into the active site
Enzyme stresses bonds
on substrate
Enzymes can build molecules
Substrate molecules can only bond one way.
Substrate moleculesfit into the active site in the best position to bond Once in the active site, the molecules of
substrate join
Enzyme InhibitorsInhibitors control the rate of enzyme activity - if there is too much of an enzyme’s product,
inhibitors can slow or even stop an enzyme’s activity
Two types of Inhibition - Competitive - Non
Competitive
Competitive InhibitionThe inhibitor is a molecule that can occupy part
of the active siteWhile the inhibitor is in the active site,
substrate can’t bind with the enzyme – inhibitors compete with the substrate for the active site
inhibitor competes with substrate inhibitor blocks the active site
Noncompetitive InhibitionThe inhibitor binds with the enzyme at a site away
from the active site.Inhibitor causes enzyme to change shape – prevents substrate from entering the active site
Inhibitor binds with enzyme Enzyme changes shape keeps substrate from active site
Feedback Inhibition Enzymes are often part of
a series of reactions called a biochemical pathway
- the product of one enzyme acts as the substrate for another enzyme
-the final product – acts as an inhibitor for the first enzyme in the pathway
- this stops the pathway and the production of the end-product stops as well
Feedback InhibitionThe end-product of the pathway is used for otherpurposes
As the end-product isused, its concentrationdrops
When the concentrationof the end-product dropsto a low level, inhibition endsand the enzyme pathway resumes operation
Co-Enzymes and Co-factorsCo-enzymes and Co-factors are molecules
that help certain enzymes to catalyze a reaction
- co-enzymes and co-factors often act as carriers of electrons, atoms or functional groups needed to complete a reaction.
Co-Enzymes and Co-Factors - while they bind to an enzyme’s active site, and
participate in the reaction, they are not changed by the reaction and aren’t considered substrates.
- Co-enzymes are organic molecules and include: NAD, NADP, FAD, vitamin B 1, vitamin B 6, and vitamin B 12
- Co-factors are inorganic molecules and include dietary minerals like zinc, iron, copper & potassium
Denatured Enzymes• Enzymes are proteins and if they are exposed to extremes of temp or pH lose their shape
- if a protein loses its shape, it loses its function - a protein that loses its shape is said to be denatured - if an enzyme is denatured, substrate can’t enter the active site
extreme temp
or pH
Common EnzymesAmylase - breaks down starchCatalase – breaks down H2O2
DNA polymerase – joins DNA nucleotides to build DNA
Lipase – break apart fatsLactase – breaks apart lactose – milk sugarProtease- breaks apart protein molecules
-What does –ase in a molecules’ name imply?