POST LAB ENZYME CATALYSIS LAB AP Lab #2 AP Biology
Mar 26, 2015
POST LABENZYME CATALYSIS
LABAP Lab #2AP Biology
FIRST….
Let’s review the main
concepts and vocabulary!
What is an enzyme?
A specific type of proteinSpeeds up (catalyzes) chemical reactions LOWERS activation ENERGY
Are NOT used up during rxns instead are recycled/reused
Have primary, secondary, teritary, and (sometimes) quartnary structures
Can be denatured
http://www.stolaf.edu/people/giannini/flashanimat/enzymes/transition%20state.swf
What are the 4 conformational structure of a
protein?
1. Primary LINEAR amino acid sequence Peptide bonds hold protein together
2. Secondary Alpha helices and Beta pleated sheets Hydrogen bonds hold together this level
3. Tertiary More bonding/protein folding creates 3D
shape Ionic bonds, H bonds, Van der Waals forces,
disulfidge 4. Quartnary
2+ polypeptides put together (makes bigger proteins and enzymes)
http://www.stolaf.edu/people/giannini/flashanimat/proteins/protein%20structure.swf
http://www.hippocampus.org/Biology;jsessionid=1639F9E4709EA30A7D60337870E663BF•BIOMOLECULES ANIMATION: Structure/Function of Proteins
WHAT DO THE “R GROUPS” DO IN PROTEINS?
Each amino acid has UNIQUE R-groups attached to their carbon skeleton
Involved in secondary/tertiary structure bonding
Some R groups create:Nonpolar Amino Acids
(NO CHARGE!!!) Polar Amino Acids (+
or – CHARGE)
Enzyme Vocabulary Substrate = ?
SPECIFIC reactant that a SPECIFIC enzyme binds to
Active Site = ? Area on enzyme which binds to substrate
Induced fit = ?Occurs in enzyme-substrate complex
enzyme binds substrate “tighter” leading to quicker transition stateWeakens substrate bonds lowers EA
ACTIVE SITE IN AN ENZYME
http://highered.mcgraw-hill.com/sites/0072943696/student_view0/chapter2/animation__how_enzymes_work.html
WHAT IS “DENATURATION” AGAIN?
•When a protein unravels and loses its native conformation/shape
•3D shape (teritary) and secondary structures are disrupted!
•Enzyme function is lowered or stops•http://highered.mcgraw-hill.com/sites/0072943696/student_view0/chapter2/animation__protein_denaturation.html
•
WHY DOES PH DENATURE PROTEINS?
BASEexcess OH- ions
ACID =excess H+
Protein's shape is alteredActive site is blockedEnzyme cannot bind substrate and
make productes
WHY DOES TEMPERATUREDENATURE PROTEINS?
Kinetic energy changes Atoms move differently affects bonds
in protein A higher temperature generally
results in increase activity b/c molecular motion increases resulting in more molecular collisionsIf, however, temp rises above a certain
point, the heat will denature molecules move too fast and can’t H-bond
Cold temp’s SLOW DOWN or stop activity b/c molecular motion decrease
[SUBSTRATE] ALSO EFFECTS ENZYME ACTIVITY
If [ ] of enzyme is constant… at lower [substrate] [substrate]=
limiting factor As [substrate] increases, RATE of
enzyme activity also increasesHowever, at very high [substrate]
enzymes become saturated with substrate and a higher concentration of substrate does NOTHING to increase the reaction rateAll the enzymes are already in use
GRAPHS
POST LAB…
Lab #2: Enzyme
Catalysis
What is the substrate used in lab= ? H2O2 (hydrogen peroxide)
What is the enzyme used in lab= ? Catalase
What are the products used in lab= ? H2O (water) and O2 (oxygen gas)
CATALASE
+ O=OOxygen
gas
ENZYME
SUBSTRATE (REACTANT) PRODUCTS
NOTE: Oxygen gas(O2) forms
BUBBLES
WHY DOES H2O2 NEED TO BE BROKEN DOWN?
H2O2 is poisonous (TOXIC) to cells!H2O2 is naturally made during
cellular respiration (ATP production in cells)
REVIEW… PART A What did the catalase solution do when H2O2 was
added? Why?O2 bubbles formed
Catalase broke down H2O2 What did the liver and potato tissue do when H2O2
was added? Why?O2 bubbles formed
Catalase broke down H2O2 in BOTH tissues What did the boiled liver do when H2O2 was added?
Why? High temp’s denatured catalase enzyme
function stoppedNO bubbles (O2)
REVIEW… PART B What did we establish a BASELINE?
We needed to know HOW much H2O2 is in 3% solution
THIS IS OUR INITIAL AMOUNT OF H2O2
We put this amount of H2O2 is each cup to begin with
What did we use KMnO4 (potassium permanganate)?
Amount of KMnO4 = Amount of H2O2 LEFT inside cup
We used INITIAL and FINAL readings to determine TOTAL amount of KMnO4 in cup (equal to amount of H2O2)
TITRATION RXN
The Titration Reaction is below: 5 H2O2 + 2 KMNO4 + 3 H2SO4 K2SO4 + 2 MnSO4 + 8 H2O + 5
O2
** H2O2 reacts with 2 KMNO4 ; once H2O2 all used up KMNO4 can’t react anymore
REVIEW… PART DWhy did we use HCl (hydrochloric acid)? The hydrochloric acid (HCl) will “freeze” enzyme
reaction. WHY??? Adding H+ ions disrupts/BLOCKS active site Which cup should have the MOST H2O2 LEFT
(least amount of H2O2 decomposition)?0 sec cup. Why?
Enzyme had no time to work Which cup should have the LEAST H2O2 LEFT
(most amount of H2O2 decomposition)?360 sec cup. Why?
Enzyme had most time to work
RESULTS: ANALYSIS OF DATA
You need to: Calculate
the RATE OF ENZYMATIC REACTION
GRAPHS
CONCLUSIONS
Enzyme reaction rate is affected by:pH, temp, [substrate], & [enzyme]
SOME REAL-LIFE APPLICATIONS….
1. Bacterial enzymes and use of disinfectants Many disinfectants, such as chlorine,
iodine, iodophores, mercurials, silver nitrate, formaldehyde, and ethylene oxide, INACTIVATE bacterial enzymes and block metabolism.
2. Extremes of temperature to control bacteria. High temperatures, such as autoclaving,
boiling, and pasteurization, denature proteins and STOP functions
Cold temperatures, such as refrigeration or freezing, SLOW DOWN or STOP enzyme rxns
ENZYME TUTORIAL ANIMATION
http://www.hippocampus.org/AP%20Biology%20II Principles of Bioenergetics
View Part 1, 2, and 4