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

Side one Side two

REACTANTS PRODUCTS

Side one Side two

REACTANTS PRODUCTS

Forward reaction

Reverse reaction

Side One Side Two

Initially

15 sec.

Record data – numbers of items on each side, go to clickerQuestions #1 and #2 after 15 sec.

Clicker Question #1: Is this process…?

A) dynamic

B) static

Clicker Question #2: Has the process reached equilibrium?

A) Yes

B) No

C) Not sure

Additional Rounds (time points) – continue recording data

Side One Side Two

Time 0

15 sec.

30 sec.

45 sec.

60 sec.

Clicker Question #3: Has the process reached equilibrium now?

A) Yes

B) No

C) Not sure

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?

Suppose 20 more molecules (labeled) are added to side 1

#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