Review
The active site of an enzyme is the region that
a.
binds allosteric regulators of the enzyme.
b.
is involved in the catalytic reaction of the
enzyme.
c.
binds the products of the catalytic reaction.
d.
is inhibited by the presence of a coenzyme
or a cofactor.
e.
both A and B
AP Biology
2008-2009
Review
The active site of an enzyme is the region that
a.
binds allosteric regulators of the enzyme.
b.
is involved in the catalytic reaction of the
enzyme.
c.
binds the products of the catalytic reaction.
d.
is inhibited by the presence of a coenzyme
or a cofactor.
e.
both A and B
AP Biology
2008-2009
REVIEW
 If an enzyme solution is saturated with
substrate, the most effective way to obtain
an even faster yield of products is to
a.
add more of the enzyme.
b.
heat the solution to 90°C.
c.
add more substrate.
d.
add an allosteric inhibitor.
e.
add a noncompetitive inhibitor.
AP Biology
REVIEW
 If an enzyme solution is saturated with
substrate, the most effective way to obtain
an even faster yield of products is to
a.
add more of the enzyme.
b.
heat the solution to 90°C.
c.
add more substrate.
d.
add an allosteric inhibitor.
e.
add a noncompetitive inhibitor.
AP Biology
Review
Many different things can alter enzyme activity.
Which of the following underlie all types of
enzyme regulation?
 a. changes in the activation energy of the
reaction
 b. changes in the active site of the enzyme
 c. changes in the free energy of the reaction
 d. A and B only
 e. A, B, and C
AP Biology
Review
Many different things can alter enzyme activity.
Which of the following underlie all types of
enzyme regulation?
 a. changes in the activation energy of the
reaction
 b. changes in the active site of the enzyme
 c. changes in the free energy of the reaction
 d. A and B only
 e. A, B, and C
AP Biology
Review
How does a non-competitive inhibitor decrease the
rate of an enzyme reaction?
 a. by binding at the active site of the enzyme
 b. by changing the structure of the enzyme
 c. by changing the free energy change of the
reaction
 d. by acting as a coenzyme for the reaction
 e. by decreasing the activation energy of the
reaction
AP Biology
Review
How does a non-competitive inhibitor decrease the
rate of an enzyme reaction?
 a. by binding at the active site of the enzyme
 b. by changing the structure of the enzyme
 c. by changing the free energy change of the
reaction
 d. by acting as a coenzyme for the reaction
 e. by decreasing the activation energy of the
reaction
AP Biology
Making energy!
ATP
The point
is to make
ATP!
AP Biology
2008-2009
The energy needs of life
 Organisms are endergonic systems

What do we need energy for?
 synthesis
 building biomolecules
 reproduction
 movement
 active transport
 temperature regulation
AP Biology
Where do we get the energy from?
 Work of life is done by energy coupling

use exergonic (catabolic) reactions to
fuel endergonic (anabolic) reactions
digestion
+
synthesis
+
AP Biology
+
energy
+
energy
ATP
 Adenosine TriPhosphate

modified nucleotide
 nucleotide =
adenine + ribose + Pi  AMP
 AMP + Pi  ADP
 ADP + Pi  ATP
 adding phosphates is endergonic
How efficient!
Build once,
use many ways
AP Biology
high energy bonds
How does ATP store energy?
AMP
ADP
ATP
I think
he’s a bit
unstable…
don’t you?
O– O– O– O– O–
–O P –O
O– P –O
O––P
OO
P––O
O– P O–
O O O O O
 Each negative PO4 more difficult to add

a lot of stored energy in each bond
 most energy stored in 3rd Pi
 3rd Pi is hardest group to keep bonded to molecule
 Bonding of negative Pi groups is unstable


spring-loaded
Pi groups “pop” off easily & release energy
AP Biology
Instability of its P bonds makes ATP an excellent energy donor
How does ATP transfer energy?
ADP
ATP
O– O– O–
–O P –O
O– P –O
O– P O–
O O O
O–
–O P O – +
O
7.3
energy
 ATP  ADP

releases energy
 ∆G = -7.3 kcal/mole
 Fuel other reactions
 Phosphorylation

released Pi can transfer to other molecules
 destabilizing the other molecules
AP Biology
enzyme that phosphorylates = “kinase”
ATP / ADP cycle
Can’t store ATP
cellular
 good energy donor,
not good energy storage respiration
 too reactive
 transfers Pi too easily
 only short term energy
storage
 carbohydrates & fats are
long term energy storage
Whoa!
Pass me
the glucose
(and O2)!
AP Biology
ATP
7.3
kcal/mole
ADP + Pi
A working muscle recycles over
10 million ATPs per second
Oxidation - definitions
 Loss of electrons.
 Loss of energy.
 Loss of Hydrogens from Carbons.
AP Biology
Be careful not
Reduction - definitions
to use “reduction”
in lay terms!
 Gain of electrons.
 Gain of energy.
 Gain of Hydrogens to Carbons.
AP Biology
Overview of cellular respiration
 4 metabolic stages

Anaerobic respiration
1. Glycolysis
 respiration without O2
 in cytosol

Aerobic respiration
 respiration using O2
 in mitochondria
2. Pyruvate oxidation
3. Citric Acid Cycle
4. Electron transport chain
C H O6 +
AP Biology
6 12
6O2
 ATP + 6H2O + 6CO2 (+ heat)
Cells spend a lot of time making ATP!
The
point is to make
ATP!
What’s the
point?
AP Biology
Review
What is the term used for the metabolic
pathway in which glucose (C6H12O6) is
degraded to carbon dioxide (CO2) and
water?
 a. cellular respiration
 b. glycolysis
 c. fermentation
 d. citric acid cycle
 e. oxidative phosphorylation
AP Biology
Review
What is the term used for the metabolic
pathway in which glucose (C6H12O6) is
degraded to carbon dioxide (CO2) and
water?
 a. cellular respiration
 b. glycolysis
 c. fermentation
 d. citric acid cycle
 e. oxidative phosphorylation
AP Biology
Review
Which of the following statements is (are) correct
about an oxidation-reduction (or redox) reaction?
 a. The molecule that is reduced gains electrons.
 b. The molecule that is oxidized loses electrons.
 c. The molecule that is reduced loses electrons.
 d. The molecule that is oxidized gains electrons.
 e. Both A and B are correct.
AP Biology
Review
Which of the following statements is (are) correct
about an oxidation-reduction (or redox) reaction?
 a. The molecule that is reduced gains electrons.
 b. The molecule that is oxidized loses electrons.
 c. The molecule that is reduced loses electrons.
 d. The molecule that is oxidized gains electrons.
 e. Both A and B are correct.
AP Biology
Review
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
Review
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
Cellular Respiration
Stage 1:
Glycolysis
AP Biology
2007-2008
Glycolysis
 Breaking down glucose

“glyco – lysis” (splitting sugar)
glucose      pyruvate
2x 3C
6C

ancient pathway which harvests energy
 where energy transfer first evolved
 transfer energy from organic molecules to ATP
 still is starting point for ALL cellular respiration

but it’s inefficient
 generate only 2 ATP for every 1 glucose

occurs in cytosol
AP Biology
That’s not enough
ATP for me!
In the
cytosol?
Why does
that make
evolutionary
sense?
Evolutionary perspective
 Prokaryotes

first cells had no organelles
Enzymes
of glycolysis are
“well-conserved”
 Anaerobic atmosphere


life on Earth first evolved without free oxygen (O2)
in atmosphere
energy had to be captured from organic molecules
in absence of O2
 Prokaryotes that evolved glycolysis are ancestors
of all modern life

AP Biology
ALL cells still utilize glycolysis
Overview
glucose
C-C-C-C-C-C
10 reactions
enzyme
2 ATP
enzyme
2 ADP
convert
fructose-1,6bP
glucose (6C) to
P-C-C-C-C-C-C-P
enzyme
enzyme
2 pyruvate (3C)
enzyme
DHAP
G3P
 produces:
4 ATP & 2 NADH P-C-C-C C-C-C-P
2H
 consumes:
2Pi enzyme
2 ATP
enzyme
 net yield:
2Pi
enzyme
2 ATP & 2 NADH

DHAP = dihydroxyacetone phosphate
AP Biology
G3P
= glyceraldehyde-3-phosphate
pyruvate
C-C-C
2 NAD+
2
4 ADP
4 ATP
Glycolysis summary
endergonic
invest some ATP
ENERGY INVESTMENT
-2 ATP
ENERGY PAYOFF
G3P
C-C-C-P
4 ATP
exergonic
harvest a little
ATP & a little NADH
like $$
in the
bank
NET YIELD
AP Biology
net yield
2 ATP
2 NADH
1st half of glycolysis (5 reactions)
Glucose “priming”

get glucose ready
to split
 phosphorylate
CH2 O
O
P
Glucose 6-phosphate
2
P O
ADP
CH2 O
O
P
CH2
CH2
CH2OH
O
Fructose 1,6-bisphosphate
O CH2
C
4,5 aldolase
isomerase
O Dihydroxyacetone
CH2OH phosphate
Glyceraldehyde 3
-phosphate (G3P)
Pi
NAD+
Pi
6
glyceraldehyde
NADH
NADH
3-phosphate
P
dehydrogenase
1,3-Bisphosphoglycerate 1,3-Bisphosphoglycerate
(BPG)
(BPG)
H
C O
CHOH
CH2 O
NAD+
AP Biology
O
Fructose 6-phosphate
3
ATP
phosphofructokinase
split destabilized
glucose
P
ADP
phosphoglucose
isomerase
glucose
 molecular
rearrangement

CH2OH
Glucose
1
ATP
hexokinase
O
P
O
CHOH
CH2 O
P
O
P
2nd half of glycolysis (5 reactions)
DHAP
P-C-C-C
Energy Harvest

NADH production
 oxidizes the sugar
 reduces NAD+
 NAD+  NADH

ATP production
 G3P    pyruvate
 “substrate level
phosphorylation”
 ADP  ATP
NAD+
Pi
G3P
C-C-C-P
AP Biology
NAD+
NADH
NADH
7
phosphoglycerate
kinase
ADP
ATP
3-Phosphoglycerate
(3PG)
ADP
ATP
3-Phosphoglycerate
(3PG)
8
phosphoglyceromutase
2-Phosphoglycerate
(2PG)
ADP
CHOH
CH2
O P
C O
H C O
CH2OH
P
OH2O
Phosphoenolpyruvate
(PEP)
10
pyruvate kinase
ADP
ATP
ATP
Pyruvate
OC
O-
2-Phosphoglycerate
(2PG)
9
enolase
H2O
Phosphoenolpyruvate
(PEP)
Payola!
Finally some
ATP!
Pi
6
Pyruvate
C
O
C O
CH2
OC
O
C
O
CH3
P
Energy accounting of glycolysis
2 ATP
2 ADP
glucose      pyruvate
2x 3C
6C
4 ADP
4 ATP
2 NAD+
2
 Net gain = 2 ATP + 2 NADH


All that work!
And that’s all
I get?
But
glucose has
so much more
to give!
some energy investment (-2 ATP)
small energy return (4 ATP + 2 NADH)
AP 1Biology
6C sugar  2 3C sugars
Is that all there is?
 Not a lot of energy…

for 1 billon years+ this is how life on
Earth survived
 no O2 = slow growth, slow reproduction
 only harvest 3.5% of energy stored in glucose
 more carbons to strip off = more energy to harvest
O2
O2
O2
O2
AP Biology
O2
glucose     pyruvate
2x 3C
6C
Hard way
to make
a living!
But can’t stop there!
G3P
DHAP
NAD+
raw materials  products
Pi
+
NADH
NAD
NADH
Pi
1,3-BPG
NAD+
Pi
+
NADH
NAD
1,3-BPG
NADH
7
ADP
Glycolysis
6
Pi
ADP
ATP
ATP
3-Phosphoglycerate
(3PG)
3-Phosphoglycerate
(3PG)
2-Phosphoglycerate
(2PG)
2-Phosphoglycerate
(2PG)
glucose + 2ADP + 2Pi + 2 NAD+  2 pyruvate + 2ATP
+ 2NADH
8
 Going to run out of NAD+


9
H2O
without regenerating NAD+,
energy production would stop! Phosphoenolpyruvate
(PEP)
another molecule must accept HADP
10
from NADH
ATP
 so
AP Biology
NAD+ is freed up for another round
Pyruvate
H2O
Phosphoenolpyruvate
(PEP)
ADP
ATP
Pyruvate
How is NADH recycled to NAD+?
Another molecule
must accept H
from NADH
H2O
O2
recycle
NADH
with oxygen
without oxygen
aerobic respiration
anaerobic respiration
“fermentation”
pyruvate
NAD+
NADH
acetyl-CoA
CO2
NADH
NAD+
lactate
acetaldehyde
NADH
NAD+
lactic acid
fermentation
which path you
use depends on
AP Biology
who
you are…
Krebs
cycle
ethanol
alcohol
fermentation
Fermentation (anaerobic)
 Bacteria, yeast
pyruvate  ethanol + CO2
3C
NADH
2C
NAD+
 beer, wine, bread
1C
back to glycolysis
 Animals, some fungi
pyruvate  lactic acid
3C
NADH

AP Biology
3C
NAD+back to glycolysis
cheese, anaerobic exercise (no O2)
Alcohol Fermentation
pyruvate  ethanol + CO2
3C
NADH
2C
NAD+ back to glycolysis
 Dead end process
 at ~12% ethanol,
kills yeast
 can’t reverse the
reaction
AP Biology
1C
bacteria
yeast
recycle
NADH
Lactic Acid Fermentation
pyruvate  lactic acid

3C
NADH
3C
NAD+ back to glycolysis
 Reversible process
 once O2 is available,
lactate is converted
back to pyruvate by
the liver
AP Biology
O2
animals
some fungi
recycle
NADH
Pyruvate is a branching point
Pyruvate
O2
O2
fermentation
anaerobic
respiration
mitochondria
Krebs cycle
aerobic respiration
AP Biology
What’s the
point?
The point
is to make
ATP!
ATP
AP Biology
2007-2008