October 15 AP Biology - John D. O`Bryant School of Math & Science
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Transcript October 15 AP Biology - John D. O`Bryant School of Math & Science
AP Biology
John D. O’Bryant School of
Mathematics and Science
October 15, 2012
AP Biology
Agenda
Do Now (Quiz)
“Why is Patrick Paralyzed?” (case study)
Exam 1 discussion
“Lorenzo’s Oil” (?)
AP Biology
Do Now (Quiz)
1. Some bacteria are metabolically active in hot springs
because
A) they are able to maintain a cooler internal temperature.
B) high temperatures make catalysis unnecessary.
C) their enzymes have high optimal temperatures.
D) their enzymes are completely insensitive to temperature.
E) they use molecules other than proteins or RNAs as their
main catalysts.
AP Biology
Do Now (Quiz)
2. Which of the following statements describes enzyme
cooperativity?
A) A multi-enzyme complex contains all the enzymes of a
metabolic pathway.
B) A product of a pathway serves as a competitive inhibitor
of an early enzyme in the pathway.
C) A substrate molecule bound to an active site affects the
active site of several subunits.
D) Several substrate molecules can be catalyzed by the
same enzyme.
E) A substrate binds to an active site and inhibits
cooperation between enzymes in a pathway.
AP Biology
Do Now (Quiz)
3. A series of enzymes catalyze the reaction X → Y → Z →
A. Product A binds to the enzyme that converts X to Y at a
position remote from its active site. This binding decreases
the activity of the enzyme. What is substance X?
A) a coenzyme
B) an allosteric inhibitor
C) a substrate
D) an intermediate
E) the product
AP Biology
Do Now (Quiz)
4. A series of enzymes catalyze the reaction X → Y → Z →
A. Product A binds to the enzyme that converts X to Y at a
position remote from its active site. This binding decreases
the activity of the enzyme. Substance A functions as
A) a coenzyme.
B) an allosteric inhibitor.
C) the substrate.
D) an intermediate.
E) a competitive inhibitor.
AP Biology
Do Now (Quiz)
5. The molecule that functions as the reducing agent
(electron donor) in a redox or oxidation-reduction reaction
A) gains electrons and gains energy.
B) loses electrons and loses energy.
C) gains electrons and loses energy.
D) loses electrons and gains energy.
E) neither gains nor loses electrons, but gains or loses
energy.
AP Biology
Do Now (Quiz)
6. Using a series of arrows, draw the branched metabolic
reaction pathway described by the following statements.
∙ L can form either M or N.
∙ M can form O.
∙ O can form either P or R.
∙ P can form Q.
∙ R can form S.
∙ O inhibits the reaction of L to form M.
∙ Q inhibits the reaction of O to form P.
∙ S inhibits the reaction of O to form R.
AP Biology
Do Now (Quiz)
7. According to the figure you created from question 6,
which reaction would prevail if both Q and S were present
in the cell in high concentrations?
A) L → M
B) M → O
C) L → N
D) O → P
E) R → S
AP Biology
Metabolism & Enzymes
AP Biology
2007-2008
Factors that Affect Enzymes
AP Biology
2007-2008
Factors Affecting Enzyme Function
Enzyme concentration
Substrate concentration
Temperature
pH
Salinity
Activators
Inhibitors
AP Biology
catalase
Enzymes and temperature
Different enzymes function in different
organisms in different environments
reaction rate
human enzyme
hot spring
bacteria enzyme
37°C
AP Biology
temperature
70°C
(158°F)
How do ectotherms do it?
AP Biology
pH
What’s
happening here?!
trypsin
reaction rate
pepsin
pepsin
trypsin
0
AP Biology
1
2
3
4
5
6
pH
7
8
9
10
11
12
13
14
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 (end 10/11)
optimal pH?
most human enzymes = pH 6-8
depends on localized conditions
pepsin (stomach) = pH 2-3
trypsin (small intestines) = pH 8
AP Biology
0 1 2 3 4 5 6 7 8 9 10 11
Salinity
reaction rate
What’s
happening here?!
salt concentration
AP Biology
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!
AP Biology
Compounds which help enzymes
Fe in
Activators
hemoglobin
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
AP Biology
many vitamins
NAD (niacin; B3)
FAD (riboflavin; B2)
Coenzyme A
Mg in
chlorophyll
Compounds which regulate enzymes
Inhibitors
molecules that reduce enzyme activity
competitive inhibition
noncompetitive inhibition
irreversible inhibition
feedback inhibition
AP Biology
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
AP Biology
saturate solution with substrate
so it out-competes inhibitor
for active site on enzyme
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 poisoning
irreversible inhibitor of Cytochrome C,
an enzyme in cellular respiration
stops production of ATP
AP Biology
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
AP Biology
doesn’t breakdown the neurotransmitter,
acetylcholine
Allosteric regulation
Conformational changes by regulatory
molecules
inhibitors
keeps enzyme in inactive form
activators
keeps enzyme in active form
AP Biology Conformational
changes
Allosteric regulation
Metabolic pathways
ABCDEFG
5
6
enzyme enzyme enzyme
enzyme enzyme enzyme
enzyme
1
2
3
4
Chemical reactions of life
are organized in pathways
AP Biology
divide chemical reaction
into many small steps
artifact of evolution
efficiency
intermediate branching points
control = regulation
Efficiency
Organized groups of enzymes
enzymes are embedded in membrane
and arranged sequentially
Link endergonic & exergonic reactions
Whoa!
All that going on
in those little
mitochondria!
AP Biology
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
ABCDEFG
1
2
3
4
5
6
X
enzyme enzyme enzyme enzyme enzyme enzyme
AP Biology
allosteric inhibitor of enzyme 1
threonine
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
AP Biology
isoleucin
e
Don’t be inhibited!
Ask Questions!
AP Biology
2007-2008
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
O2 to bind
AP3Biology
Lorenzo’s Oil
AP Biology