AP Biology Lecture #14 Enzymes. 2007-2008 Factors that Affect Enzymes.
Transcript of AP Biology Lecture #14 Enzymes. 2007-2008 Factors that Affect Enzymes.
![Page 1: AP Biology Lecture #14 Enzymes. 2007-2008 Factors that Affect Enzymes.](https://reader030.fdocuments.us/reader030/viewer/2022032612/56649ef45503460f94c07b29/html5/thumbnails/1.jpg)
AP Biology
Lecture #14Enzymes
![Page 2: AP Biology Lecture #14 Enzymes. 2007-2008 Factors that Affect Enzymes.](https://reader030.fdocuments.us/reader030/viewer/2022032612/56649ef45503460f94c07b29/html5/thumbnails/2.jpg)
2007-2008
Factors that Affect Enzymes
![Page 3: AP Biology Lecture #14 Enzymes. 2007-2008 Factors that Affect Enzymes.](https://reader030.fdocuments.us/reader030/viewer/2022032612/56649ef45503460f94c07b29/html5/thumbnails/3.jpg)
Factors Affecting Enzyme Function• Enzyme concentration• Substrate concentration• Temperature • pH• Salinity• Activators• Inhibitors
catalase
![Page 4: AP Biology Lecture #14 Enzymes. 2007-2008 Factors that Affect Enzymes.](https://reader030.fdocuments.us/reader030/viewer/2022032612/56649ef45503460f94c07b29/html5/thumbnails/4.jpg)
Enzyme concentration
enzyme concentration
reac
tion
rate
What’shappening here?!
![Page 5: AP Biology Lecture #14 Enzymes. 2007-2008 Factors that Affect Enzymes.](https://reader030.fdocuments.us/reader030/viewer/2022032612/56649ef45503460f94c07b29/html5/thumbnails/5.jpg)
Factors affecting enzyme function • Enzyme concentration – as enzyme = reaction rate• more enzymes = more frequently collide with substrate
– reaction rate levels off• substrate becomes limiting factor• not all enzyme molecules can find substrate
enzyme concentration
reac
tion
rate
![Page 6: AP Biology Lecture #14 Enzymes. 2007-2008 Factors that Affect Enzymes.](https://reader030.fdocuments.us/reader030/viewer/2022032612/56649ef45503460f94c07b29/html5/thumbnails/6.jpg)
Substrate concentration
substrate concentration
reac
tion
rate
What’shappening here?!
![Page 7: AP Biology Lecture #14 Enzymes. 2007-2008 Factors that Affect Enzymes.](https://reader030.fdocuments.us/reader030/viewer/2022032612/56649ef45503460f94c07b29/html5/thumbnails/7.jpg)
Factors affecting enzyme function
substrate concentration
reac
tion
rate
• Substrate concentration – as substrate = reaction rate• more substrate = more frequently collide with enzyme
– reaction rate levels off• all enzymes have active site engaged• enzyme is saturated• maximum rate of reaction
![Page 8: AP Biology Lecture #14 Enzymes. 2007-2008 Factors that Affect Enzymes.](https://reader030.fdocuments.us/reader030/viewer/2022032612/56649ef45503460f94c07b29/html5/thumbnails/8.jpg)
37°
Temperature
temperature
reac
tion
rate
What’shappening here?!
![Page 9: AP Biology Lecture #14 Enzymes. 2007-2008 Factors that Affect Enzymes.](https://reader030.fdocuments.us/reader030/viewer/2022032612/56649ef45503460f94c07b29/html5/thumbnails/9.jpg)
Factors affecting enzyme function• Temperature– Optimum T° • greatest number of molecular collisions• human enzymes = 35°- 40°C – body temp = 37°C
– Heat: increase beyond optimum T°• increased energy level of molecules disrupts bonds in
enzyme & between enzyme & substrate– H, ionic = weak bonds
• denaturation = lose 3D shape (3° structure)– Cold: decrease T°• molecules move slower • decrease collisions between enzyme & substrate
![Page 10: AP Biology Lecture #14 Enzymes. 2007-2008 Factors that Affect Enzymes.](https://reader030.fdocuments.us/reader030/viewer/2022032612/56649ef45503460f94c07b29/html5/thumbnails/10.jpg)
Enzymes and temperature• Different enzymes function in different
organisms in different environments
37°Ctemperature
reac
tion
rate
70°C
human enzymehot springbacteria enzyme
(158°F)
![Page 11: AP Biology Lecture #14 Enzymes. 2007-2008 Factors that Affect Enzymes.](https://reader030.fdocuments.us/reader030/viewer/2022032612/56649ef45503460f94c07b29/html5/thumbnails/11.jpg)
How do ectotherms do it?
![Page 12: AP Biology Lecture #14 Enzymes. 2007-2008 Factors that Affect Enzymes.](https://reader030.fdocuments.us/reader030/viewer/2022032612/56649ef45503460f94c07b29/html5/thumbnails/12.jpg)
7
pH
pH
reac
tion
rate
20 1 3 4 5 6 8 9 10
pepsin trypsin
What’shappening here?!
11 12 13 14
pepsin
trypsin
![Page 13: AP Biology Lecture #14 Enzymes. 2007-2008 Factors that Affect Enzymes.](https://reader030.fdocuments.us/reader030/viewer/2022032612/56649ef45503460f94c07b29/html5/thumbnails/13.jpg)
Factors affecting enzyme function• pH– changes in pH• adds or remove H+
• disrupts bonds, disrupts 3D shape – disrupts attractions between charged amino acids – affect 2° & 3° structure– denatures protein
– optimal pH?• most human enzymes = pH 6-8– depends on localized conditions– pepsin (stomach) = pH 2-3– trypsin (small intestines) = pH 8
720 1 3 4 5 6 8 9 10 11
![Page 14: AP Biology Lecture #14 Enzymes. 2007-2008 Factors that Affect Enzymes.](https://reader030.fdocuments.us/reader030/viewer/2022032612/56649ef45503460f94c07b29/html5/thumbnails/14.jpg)
Salinity
salt concentration
reac
tion
rate
What’shappening here?!
![Page 15: AP Biology Lecture #14 Enzymes. 2007-2008 Factors that Affect Enzymes.](https://reader030.fdocuments.us/reader030/viewer/2022032612/56649ef45503460f94c07b29/html5/thumbnails/15.jpg)
Factors affecting enzyme function• Salt concentration– changes in salinity• adds or removes cations (+) & anions (–)• disrupts bonds, disrupts 3D shape – disrupts attractions between charged amino acids – affect 2° & 3° structure– denatures protein
– enzymes intolerant of extreme salinity• Dead Sea is called dead for a reason!
![Page 16: AP Biology Lecture #14 Enzymes. 2007-2008 Factors that Affect Enzymes.](https://reader030.fdocuments.us/reader030/viewer/2022032612/56649ef45503460f94c07b29/html5/thumbnails/16.jpg)
Compounds which help enzymes• Activators– cofactors • non-protein, small inorganic compounds
& ions– Mg, K, Ca, Zn, Fe, Cu– bound within enzyme molecule
– coenzymes• non-protein, organic molecules – bind temporarily or permanently to
enzyme near active site• many vitamins– NAD (niacin; B3)– FAD (riboflavin; B2)– Coenzyme A
Mg inchlorophyll
Fe inhemoglobin
![Page 17: AP Biology Lecture #14 Enzymes. 2007-2008 Factors that Affect Enzymes.](https://reader030.fdocuments.us/reader030/viewer/2022032612/56649ef45503460f94c07b29/html5/thumbnails/17.jpg)
Cofactors and Coenzymes• Some enzymes need assistance in the form of
cofactors• Minerals – inorganic cofactors – Examples: Potassium, Sodium, Calcium
• Vitamins – organic cofactors or coenzymes– Examples: The specialized nucleotides NAD+ and FAD act
as cofactors for enzymatic reactions; NAD+ contains the vitamin niacin and FAD contains the vitamin riboflavin
![Page 18: AP Biology Lecture #14 Enzymes. 2007-2008 Factors that Affect Enzymes.](https://reader030.fdocuments.us/reader030/viewer/2022032612/56649ef45503460f94c07b29/html5/thumbnails/18.jpg)
Some coenzymes accept and hold onto electrons (e-) and protons (H+) during the breakdown glucose
Why are these coenzymes required?
Enzymes are not used up or modified during a reaction
If the enzyme accepted the e- or H+ it would be modified
![Page 19: AP Biology Lecture #14 Enzymes. 2007-2008 Factors that Affect Enzymes.](https://reader030.fdocuments.us/reader030/viewer/2022032612/56649ef45503460f94c07b29/html5/thumbnails/19.jpg)
Factors Affecting Enzyme Activity:Activation by Phosphorylation
![Page 20: AP Biology Lecture #14 Enzymes. 2007-2008 Factors that Affect Enzymes.](https://reader030.fdocuments.us/reader030/viewer/2022032612/56649ef45503460f94c07b29/html5/thumbnails/20.jpg)
Compounds which regulate enzymes• Inhibitors– molecules that reduce enzyme activity– competitive inhibition– noncompetitive inhibition– irreversible inhibition– feedback inhibition
![Page 21: AP Biology Lecture #14 Enzymes. 2007-2008 Factors that Affect Enzymes.](https://reader030.fdocuments.us/reader030/viewer/2022032612/56649ef45503460f94c07b29/html5/thumbnails/21.jpg)
Competitive Inhibitor • Inhibitor & substrate “compete” for active site– penicillin
blocks enzyme bacteria use to build cell walls– disulfiram (Antabuse)
treats chronic alcoholism• blocks enzyme that
breaks down alcohol • severe hangover & vomiting
5-10 minutes after drinking
• Overcome by increasing substrate concentration– saturate solution with substrate
so it out-competes inhibitor for active site on enzyme
![Page 22: AP Biology Lecture #14 Enzymes. 2007-2008 Factors that Affect Enzymes.](https://reader030.fdocuments.us/reader030/viewer/2022032612/56649ef45503460f94c07b29/html5/thumbnails/22.jpg)
Non-Competitive Inhibitor • Inhibitor binds to site other than active site– allosteric inhibitor binds to allosteric site – causes enzyme to change shape
• conformational change• active site is no longer functional binding site
– keeps enzyme inactive– some anti-cancer drugs
inhibit enzymes involved in DNA synthesis • stop DNA production• stop division of more cancer cells
– cyanide poisoningirreversible inhibitor of Cytochrome C, an enzyme in cellular respiration• stops production of ATP
![Page 23: AP Biology Lecture #14 Enzymes. 2007-2008 Factors that Affect Enzymes.](https://reader030.fdocuments.us/reader030/viewer/2022032612/56649ef45503460f94c07b29/html5/thumbnails/23.jpg)
Comparison
![Page 24: AP Biology Lecture #14 Enzymes. 2007-2008 Factors that Affect Enzymes.](https://reader030.fdocuments.us/reader030/viewer/2022032612/56649ef45503460f94c07b29/html5/thumbnails/24.jpg)
Irreversible inhibition• Inhibitor permanently binds to enzyme– competitor• permanently binds to active site
– allosteric• permanently binds to allosteric site • permanently changes shape of enzyme• nerve gas, sarin, many insecticides (malathion,
parathion…)– cholinesterase inhibitors
» doesn’t breakdown the neurotransmitter, acetylcholine
![Page 25: AP Biology Lecture #14 Enzymes. 2007-2008 Factors that Affect Enzymes.](https://reader030.fdocuments.us/reader030/viewer/2022032612/56649ef45503460f94c07b29/html5/thumbnails/25.jpg)
Allosteric regulation• Conformational changes by regulatory
molecules – inhibitors• keeps enzyme in inactive form
– activators • keeps enzyme in active form
Conformational changes Allosteric regulation
![Page 26: AP Biology Lecture #14 Enzymes. 2007-2008 Factors that Affect Enzymes.](https://reader030.fdocuments.us/reader030/viewer/2022032612/56649ef45503460f94c07b29/html5/thumbnails/26.jpg)
Allosteric regulation
![Page 27: AP Biology Lecture #14 Enzymes. 2007-2008 Factors that Affect Enzymes.](https://reader030.fdocuments.us/reader030/viewer/2022032612/56649ef45503460f94c07b29/html5/thumbnails/27.jpg)
Cooperativity • Substrate acts as an activator– substrate causes conformational
change in enzyme• induced fit
– favors binding of substrate at 2nd site– makes enzyme more active & effective• hemoglobin
Hemoglobin 4 polypeptide chains can bind 4 O2; 1st O2 binds now easier for other 3
O2 to bind
![Page 28: AP Biology Lecture #14 Enzymes. 2007-2008 Factors that Affect Enzymes.](https://reader030.fdocuments.us/reader030/viewer/2022032612/56649ef45503460f94c07b29/html5/thumbnails/28.jpg)
Coupled Reactions Involving Enzymes
![Page 29: AP Biology Lecture #14 Enzymes. 2007-2008 Factors that Affect Enzymes.](https://reader030.fdocuments.us/reader030/viewer/2022032612/56649ef45503460f94c07b29/html5/thumbnails/29.jpg)
allosteric inhibitor of enzyme 1
Feedback Inhibition• Regulation & coordination of production– product is used by next step in pathway– final product is inhibitor of earlier step
• allosteric inhibitor of earlier enzyme• feedback inhibition
– no unnecessary accumulation of product
A B C D E F G enzyme1
enzyme2
enzyme3
enzyme4
enzyme5
enzyme6
X
![Page 30: AP Biology Lecture #14 Enzymes. 2007-2008 Factors that Affect Enzymes.](https://reader030.fdocuments.us/reader030/viewer/2022032612/56649ef45503460f94c07b29/html5/thumbnails/30.jpg)
Feedback inhibition• Example– synthesis of amino acid,
isoleucine from amino acid, threonine
– isoleucine becomes the allosteric inhibitor of the first step in the pathway• as product accumulates it
collides with enzyme more often than substrate does
threonine
isoleucine
![Page 31: AP Biology Lecture #14 Enzymes. 2007-2008 Factors that Affect Enzymes.](https://reader030.fdocuments.us/reader030/viewer/2022032612/56649ef45503460f94c07b29/html5/thumbnails/31.jpg)
Normal Enzematic Activity Compared to Inhibited Activity
![Page 32: AP Biology Lecture #14 Enzymes. 2007-2008 Factors that Affect Enzymes.](https://reader030.fdocuments.us/reader030/viewer/2022032612/56649ef45503460f94c07b29/html5/thumbnails/32.jpg)
Oxidation/Reduction (Redox) ReactionsOne compound gains e- or H+ lost by another compound
The oxidized compound loses electrons or H+
The reduced compound gains electrons or H+
Reduction acts as a mechanism for storing energy
![Page 33: AP Biology Lecture #14 Enzymes. 2007-2008 Factors that Affect Enzymes.](https://reader030.fdocuments.us/reader030/viewer/2022032612/56649ef45503460f94c07b29/html5/thumbnails/33.jpg)
Oxidation/Reduction (Redox) Reactions
![Page 34: AP Biology Lecture #14 Enzymes. 2007-2008 Factors that Affect Enzymes.](https://reader030.fdocuments.us/reader030/viewer/2022032612/56649ef45503460f94c07b29/html5/thumbnails/34.jpg)
2007-2008
Don’t be inhibited! Ask Questions!