1. POST LAB ENZYME CATALYSIS LAB
AP Lab #2
AP Biology

2. Let’s review the main concepts and vocabulary!
FIRST….
Let’s review the main concepts and vocabulary!

3. What is an enzyme? A specific type of protein
Speeds 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

4. http://www.stolaf.edu/people/giannini/flashanima t/enzymes/transition%20state.swf

5. What are the 4 conformational structure of a protein?
Primary
LINEAR amino acid sequence
Peptide bonds hold protein together
Secondary
Alpha helices and Beta pleated sheets
Hydrogen bonds hold together this level
Tertiary
More bonding/protein folding  creates 3D shape
Ionic bonds, H bonds, Van der Waals forces, disulfidge
Quartnary
2+ polypeptides put together (makes bigger proteins and enzymes)

6.
BIOMOLECULES ANIMATION: Structure/Function of Proteins

7. 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)

8. Enzyme Vocabulary Substrate = ? Active Site = ? Induced fit = ?
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 state
Weakens substrate bonds  lowers EA

9. ACTIVE SITE IN AN ENZYME
hill.com/sites/ /student_view0/chapter2/animation__how_e nzymes_work.html

10. 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

11. WHY DOES PH DENATURE PROTEINS?
BASE
excess OH- ions
ACID =
excess H+
Protein's shape is altered
Active site is blocked
Enzyme cannot bind substrate and make productes

12. WHY DOES TEMPERATURE DENATURE 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 collisions
If, 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

13. [SUBSTRATE] ALSO EFFECTS ENZYME ACTIVITY
If [ ] of enzyme is constant…
at lower [substrate]  [substrate]= limiting factor
As [substrate] increases, RATE of enzyme activity also increases
However, at very high [substrate]  enzymes become saturated with substrate and a higher concentration of substrate does NOTHING to increase the reaction rate
All the enzymes are already in use

14. GRAPHS

15. Lab #2: Enzyme Catalysis
POST LAB…
Lab #2: Enzyme Catalysis

16. + O=O 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=O
Oxygen gas

17. NOTE: Oxygen gas(O2) forms BUBBLES
ENZYME
SUBSTRATE (REACTANT)
PRODUCTS

18. 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)

19. 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?
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 stopped
NO bubbles (O2)

20. 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

21. We used INITIAL and FINAL readings to determine TOTAL amount of KMnO4 in cup (equal to amount of H2O2)

22. 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

23. REVIEW… PART D Why 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

24. RESULTS: ANALYSIS OF DATA
You need to: Calculate the RATE OF ENZYMATIC REACTION

25. GRAPHS

26. CONCLUSIONS Enzyme reaction rate is affected by:
pH, temp, [substrate], & [enzyme]

27. SOME REAL-LIFE APPLICATIONS….
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.
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

28. ENZYME TUTORIAL ANIMATION
Principles of Bioenergetics
View Part 1, 2, and 4