chemistry/biology interface equilibrium and enzyme kinetics (the worst 20 minutes of your...
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Chemistry/Biology InterfaceEquilibrium and Enzyme Kinetics
(The worst 20 minutes of your life…maybe?)
Reactionaries striving for equilibrium:Roberta Attanasio, Georgia State UniversityJung Choi, Georgia Institute of TechnologySteven Pomarico, Louisiana State UniversityWilliam A. Said, Georgia State UniversityTony Schwacha, University of PittsburghRupal Thazhath, Georgia Institute of TechnologyGrover Waldrop, Louisiana State University
Lillian Tong, Facilitator
Chemical Principles of Biology
• Part of an Introductory Biology course for either majors or non-majors
• Typically follows units on atoms, water and biomolecules
• Precedes units on bioenergetics
Course Learning Goals Applicable to Chemistry/Biology Interface
• Integrate principles of chemistry and physics to model biological systems
• Practice the process of science– Observation/data collection and analysis– Hypothesis generation and testing– Collaboration with others
Chemical equilibriumdemonstration
Equilibrium and enzyme kinetics – the worst 20 minutes of your life, maybe
Introduction to chemical equilibrium
Define chemical equilibrium
Clicker questions about equilibrium
Chemical equilibriumdemonstration revisited
Concept map dealing with
chemical equilibrium
Data collection
Data collection
Explanation chemical equilibrium constant
Clicker questions about chemical
equilibrium
Compare withpredictions
Inferring predictions
about demonstration
Pre-assessment forequilibrium and kinetics
= Assessment
= Lecture
= Data collection
= Active learning
Group brainstormingsession
Small discussion groupquestion
Introduction to enzyme kinetics
Enzyme kineticsclicker questions
Return to concept mapwith addition of enzymes
Take home assignment
Post unit assessment
Chemical Equilibrium Learning Goals
Students should be able to apply the principles of chemical equilibrium to explain dynamic biological processes such as antigen-antibody, ligand-receptor, and enzyme-substrate interactions.
Explain chemical equilibrium in terms of reactants and products – experiment with balls
Define equilibrium constant – experiment with balls Given the equilibrium constant, predict in which direction the
reaction will go – experiment with balls Demonstrate that equilibrium systems are dynamic with no
net change – experiment with balls
An experiment about equilibrium
• Items (colored balls) represent chemicals• Locations (different sides of the room) represent
different chemical states• Equal numbers of student volunteers on both sides of
the room. • On side1, students clap once, pick up balls and throw
them to side 2 one at a time (represents forward rate).
• On side 2, students face backwards, pick up a ball and then toss it to side 1 (represents reverse rate).
• Count balls on each side at 15-20 sec. intervals
Side One Side Two
Initially
15 sec.
Record data – numbers of items on each side, go to clickerQuestions #1 and #2 after 15 sec.
Additional Rounds (time points) – continue recording data
Side One Side Two
Time 0
15 sec.
30 sec.
45 sec.
60 sec.
We have reached a condition where the amount on each side remains constant, even though things are still
in motion. This is called equilibrium.
We can describe this condition in terms that relate the amount on side One (the reactants) to the
amount on side Two (the products)
Equilibrium constant
Think-pair-share: what is the equilibrium constant, and how would you describe in an equation the final condition in this experiment?
#4: Suppose 20 more items are added to side One. The equilibrium constant will
A) stay the same
B) increase
C) decrease
#5: Suppose 20 more items are added to side One. Items will move from
A) Side One to side Two
B) Side Two to side One
C) Both
D) Neither
#6: Suppose 20 more items are added to side One. In order to re-establish equilibrium, there
will be a net transfer of items
A) Side One to side Two
B) Side Two to side One
C) No net transfer will occur
Side One Side Two
Initially
Initially
15 Sec.
15 Sec.
30 Sec.
30 Sec.
Let’s redo the experiment with 20 additional labeled molecules to Side One
Do these data fit your predictions?
Products
Reactants
Forward rate
Reverse rate
Chemicalequilibrium
involves
? You describe this
Chemicalreactions
Free energy
Has higher energy
Has lower energy
Fill in the blue ovals, and add appropriate words to go with each arrow.
Group brainstorming session
• For next 5 minutes, discuss and list analogies for equilibrium in everyday life.
• We’ll select random groups to report verbally to rest of class.
ProductsReactantsconverts to
converts to
Chemicalequilibrium
involves
is theratio of reactants
to products
Chemicalreactions
Enzymes
Productsconverts to
converts to
Chemicalequilibrium
involves
is theratio of reactants
to products
Chemicalreactions
Enzymes catalyze/speed up
ReactantsSubstrates
ProductsSubstratesconverts to
converts to
Chemicalequilibrium
involves
is theratio of reactants
to products
Chemicalreactions
Enzymes catalyze/speed up
determines
Thermodynamics determinesthe direction of
Enzyme kinetics learning goals
• Explain the relationship between substrate concentration and the velocity of the reaction.
• Apply enzyme kinetics to explain physiological processes.
One enzymatic reaction:
• Glucose + ATP Glucose-6-P + ADP• Enzyme assay: measure G-6-P produced over
time, at different concentrations of glucose• Graph the slope (velocity = rate of product
formation) as a function of glucose concentration = [glucose]
Glucose is the substrate for two enzymes in the liver, hexokinase (HKase) and glucokinase (Gkase).
Their kinetics are shown in the figure.
Glucose is the substrate for two enzymes in the liver, hexokinase (HKase) and glucokinase
(Gkase). Their kinetics are shown in the figure.
Glucose is the substrate for two enzymes in the liver, hexokinase (HKase) and glucokinase
(Gkase). Their kinetics are shown in the figure.
Vmax
½ Vmax
Km
Glucose is the substrate for two enzymes in the liver, hexokinase (Hkase) and glucokinase
(Gkase). Their kinetics are shown in the figure.
Vmax
Vmax
Km Km
Hkase
Gkase
Why does the velocity plateau?
A) All the enzyme molecules are occupiedB) The enzyme stops workingC) Substrate is depleted
Gkase
HkaseVmax
Vmax
Km Km
Hkase
Gkase
Vmax
Vmax
Km Km
Hkase
Gkase
You haven’t eaten all day; your blood sugar is low. Which enzyme shows greater velocity?
A) hexokinaseB) glucokinase
Vmax
Vmax
Km Km
Hkase
Gkase
You eat a dozen glazed donuts, and your blood sugar skyrockets. Now which
enzyme has greater velocity?
• A) hexokinase
• B) glucokinase
Vmax
Vmax
Km Km
Hkase
Gkase
Small group discussion question:
• What would happen in people missing glucokinase?
Homework Assignment:
• Go to www.ncbi.nlm.nih.gov
• Click on OMIM (On-line Mendelian Inheritance in Man)
• Search for an enzyme deficiency.
• Turn in a one-page summary.
• 5 students selected at random will be called at next class to report.
Active Learning Components
• Clicker questions• Experiment about equilibrium• Concept mapping• Group activity – brainstorming for applications of
equilibrium to their daily lives• Homework assignment about enzyme deficiencies
Assessment
• Pre- and post-test for unit• Clicker questions – formative assessment• Concept map at end of chemical equilibrium unit –
formative assessment• Group brainstorming activity• Follow on questions in subsequent units: enzymes,
facilitated diffusion, chemiosmosis, cell signaling (receptor-ligand), antigen-antibody interactions, transcription factor binding, etc.
Addressing a Diversity of Learning Styles, Backgrounds
• Experiment is kinesthetic and visual• Recording numerical data – analytic• Brainstorming session on application addresses big picture
and is inclusive, as well as encouraging each to construct from their own experience.
• Concept mapping for wholistic learners• Clicker questions enable all students (including the quiet
ones) to participate.• Reading assignment from textbook for verbal learners• On-line research and writing for also for verbal learners• Graph of enzyme kinetics is visual as well as analytical