Competition and cooperation are important aspects of biological systems Essential Knowledge 4B1 Interactions between molecules affect their structure and function Life requires enzymes to speed up reactions ID: 414909
Download Presentation The PPT/PDF document "Enduring Understanding:" is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
Enduring Understanding: Competition and cooperation are important aspects of biological systems
Essential Knowledge
4.B.1: Interactions between molecules affect their structure and functionSlide2
Life requires enzymes to speed up reactions
Biological Catalysts
Reduce Energy Barrier
Enzymes belong to what class of
macrmolecule
?proteinsHow do enzymes work?They lower the activation energy required to get a reactions startedSlide3
Life requires enzymes to speed up reactions
The structure of an enzyme determines its function.
Induced Fit of substrate + enzyme = enzyme substrate complex
Why is the shape of an enzyme important?
Enzymes work with specific substrates
Enzymes must be able to bind to the substrate The substrate must be complementary to the surface properties (shape and charge) of the active site
The substrate must fit into the enzyme’s active siteSlide4
Life requires enzymes to speed up reactions
Figure 8.15-3
Substrates
Substrates enter active site.
Enzyme-substrate
complex
Enzyme
Products
Substrates are held
in active site by weak
interactions.
Active site can
lower E
A
and speed
up a reaction.
Active
site is
available
for two new
substrate
molecules.
Products are
released.
Substrates are
converted toproducts.
1
2
3
4
5
6Slide5
Enzyme Facts:Enzymes are reusableEnzymes are substrate specific
Enzymes lower the activation energy of a reaction
Enzymes change shape upon binding to the substrate – thus holding the substrate in such a way to favor breaking existing bonds and making new ones – Induced Fit
Life requires enzymes to speed up reactionsSlide6
Many enzymes require nonprotein helpers in order to function
Cofactors and coenzymes interact with enzymes to cause structural changes that alter the activity rate of the enzyme
The enzyme may only become active when all the appropriate cofactors or coenzymes are present and
bind to the appropriate sites on the enzyme
Interactions between molecules affect their structure and functionSlide7
What is the difference between a cofactor and a coenzyme?Cofactor – inorganic, such as the metal atoms zinc, iron and copper in ionic form
Coenzyme – organic molecule; many are vitamins
Interactions between molecules affect their structure and functionSlide8
Other molecules and the environment in which the enzyme acts can enhance or inhibit enzyme activity. Environmental factors that may alter enzyme shape (particularly the tertiary structure) thereby altering enzyme function
Temperature
pH
Salt concentration
Interactions between molecules affect their structure and functionSlide9
Optimal temperature for
typical human enzyme (37°C)
Optimal temperature for
enzyme of thermophilic
(heat-tolerant)
bacteria (77°C)
Temperature (°C)
(a) Optimal temperature for two enzymes
Rate of reaction
Rate of reaction
120
100
80
60
40
20
0
0
1
2
3
4
5
6
7
8
9
10
pH
(b) Optimal pH for two enzymes
Optimal pH for pepsin
(stomach
enzyme)
Optimal pH for trypsin
(intestinal
enzyme)Slide10
Molecules can bind reversibly or irreversibly to an enzyme’s active site or an allosteric site – changing the activity of the enzyme
Regulation of enzyme activity helps control metabolism
Allosteric regulation – (
allo
refers to “other”) a regulatory molecule binds to the enzyme at a site other than the active site - can either speed up (activator) or slow down (inhibitor) the reaction
Cooperativity – a substrate molecule binding to one active site in a multi-subunit enzyme triggers a shape change in all the subunits – increasing the reaction
Interactions between molecules affect their structure and functionSlide11
(a) Normal binding
(b) Competitive inhibition
(c) Noncompetitive
inhibition
Substrate
Active
site
Enzyme
Competitive
inhibitor
Noncompetitive
inhibitorSlide12
Regulatory
site (one
of four)
(a) Allosteric activators and inhibitors
Allosteric enzyme
with four subunits
Active site
(one of four)
Active form
Activator
Stabilized active form
Oscillation
Non-
functional
active site
Inactive form
Inhibitor
Stabilized inactive
form
Inactive form
Substrate
Stabilized active
form
(b) Cooperativity: another type of allosteric activationSlide13
Feedback inhibition is a common mode of metabolic control. An end product of a metabolic pathway can bind to an enzyme at the start of the pathway – changing the shape of the enzyme thereby “inhibiting” the reaction from taking place
Interactions between molecules affect their structure and functionSlide14
Active site
available
Isoleucine
used up by
cell
Feedback
inhibition
Active site of
enzyme 1 is
no longer able
to catalyze the
conversion
of threonine to
intermediate A;
pathway is
switched off.
Isoleucine
binds to
allosteric
site.
Initial
substrate
(threonine)
Threoninein active site
Enzyme 1(threoninedeaminase)
Intermediate AIntermediate B
Intermediate C
Intermediate D
Enzyme 2
Enzyme 3
Enzyme 4
Enzyme 5
End product
(isoleucine)Slide15
The change in function of an enzyme can be interpreted from data regarding the concentrations of product or substrate as a function of time. These representations demonstrate the relationship between an enzyme’s activity, the disappearance of substrate, and/or presence of a competitive inhibitor.
Interactions between molecules affect their structure and functionSlide16
What could we measure?Disappearance of H20
2
Production of H
2
O and/or production of O2Heat given off
Catalase + 2H2O2
Catalase/H
2
O
2
complex
Catalase + 2H
2
O + O
2