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Presentation on theme: "POST LAB ENZYME CATALYSIS LAB AP Lab #2 AP Biology."— Presentation transcript:


2 FIRST…. Lets 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 t/enzymes/transition%20state.swf t/enzymes/transition%20state.swf

5 What are the 4 conformational s t r u c t u r e o f a p r o t e i n ? 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)

6 20structure.swf;jsessionid=1639F9E4709EA30 A7D60337870E663BF 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 = ? 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 E A

9 ACTIVE SITE IN AN ENZYME http://highered.mcgraw- nzymes_work.html http://highered.mcgraw- 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 http://highered.mcgraw- n_denaturation.htmlhttp://highered.mcgraw- n_denaturation.html

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 cant H-bond Cold temps 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


15 POST LAB… Lab #2: Enzyme Catalysis

16 What is the substrate used in lab= ? H 2 O 2 (hydrogen peroxide) What is the enzyme used in lab= ? Catalase What are the products used in lab= ? H 2 O (water) and O 2 (oxygen gas) CATALASE +O= O Oxygen gas


18 WHY DOES H 2 O 2 NEED TO BE BROKEN DOWN? H 2 O 2 is poisonous (TOXIC) to cells! H 2 O 2 is naturally made during cellular respiration (ATP production in cells)

19 REVIEW… PART A What did the catalase solution do when H 2 O 2 was added? Why? O 2 bubbles formed Catalase broke down H 2 O 2 What did the liver and potato tissue do when H 2 O 2 was added? Why? O 2 bubbles formed Catalase broke down H 2 O 2 in BOTH tissues What did the boiled liver do when H 2 O 2 was added? Why? High temps denatured catalase enzyme function stopped NO bubbles (O 2 )

20 REVIEW… PART B What did we establish a BASELINE? We needed to know HOW much H 2 O 2 is in 3% solution THIS IS OUR INITIAL AMOUNT OF H 2 O 2 We put this amount of H 2 O 2 is each cup to begin with What did we use KMnO 4 (potassium permanganate) ? Amount of KMnO 4 = Amount of H 2 O 2 LEFT inside cup

21 We used INITIAL and FINAL readings to determine TOTAL amount of KMnO 4 in cup (equal to amount of H 2 O 2 )

22 TITRATION RXN The Titration Reaction is below: 5 H 2 O 2 + 2 KMNO 4 + 3 H 2 SO4 K 2 SO 4 + 2 MnSO 4 + 8 H 2 O + 5 O 2 ** H 2 O 2 reacts with 2 KMNO 4 ; once H 2 O 2 all used up KMNO 4 cant 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 H 2 O 2 LEFT (least amount of H 2 O 2 decomposition)? 0 sec cup. Why? Enzyme had no time to work Which cup should have the LEAST H 2 O 2 LEFT (most amount of H 2 O 2 decomposition)? 360 sec cup. Why? Enzyme had most time to work



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

27 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

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

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