POST LAB ENZYME CATALYSIS LAB AP Lab #2 AP Biology

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

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