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Lecture 9

ENVS 1000U Lecture Notes - Lecture 9: Amylose, Reaction Rate, Starch


School
UOIT
Department
Environmental-Science
Course Code
ENVS 1000U
Professor
Mary Olaveson
Lecture
9

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Enzymes function and how they work
Enzymes are catalyst
o Substrate binds to the active site of the enzyme and is converted into a
reaction product
Cofactors/coenzymes and activators help with enzyme activity
Inhibitors stop substrates from binding to their active sites
Cofactors and Coenzymes and Activators
Non protein substances
Bind to active site of enzymes
Covalently bonded to active site, prosthetic group
Cofactors = metal ions like Fe, Zn, CO, Mg ect…..
Coenzymes = made from vitamins
Activators = bind to the enzyme (not necessarily to the active site), and change
the shape so that the activity of the enzyme is enhanced
Inhibitors
Either bind to the active site or bind to the enzyme somewhere else
They decrease enzyme activity
If they bind to the active site, they are usually similar in shape to the substrate
o So they compete with the substrate for the active site
o Inhibitors that compete with the substrate are called “competitive
inhibitors”
If there is a higher concentration of substrate then inhibitors, it removes the
inhibitor in “competitive inhibitors” ONLY
If the inhibitor binds somewhere else on the enzyme then it changes the shape of
the enzyme in the tertiary or quaternary structures
o These are called non-competitive inhibitors
o Inhibition CANT be reversed in this case
Enzyme rate
Enzyme rate is found experimentally by measuring;
o rate of substrate disappearance over time
or
o rate of product made over time
colorimetric assay is used to measure either one
spectrophotometer is used to measure the colorimetric assay
these curves on a graph are usually linear and reaches an evening out point (aka
plateau) when the substrate is limited
o enzymatic rate is = slope of linear portion of curve
absorbance of product appearance / time
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