Transcript AP Biology - John D. O`Bryant School of Math & Science

AP Biology
John D. O’Bryant School of
Mathematics and Science
October 25, 2012
AP Biology
Agenda
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Do Now: HW Review
Outlining: Concept 9.5
Cellular Respiration: Lecture/Discussion
Quiz
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1. A deficiency of a citric acid cycle enzyme in both
mitochondria and the cytosol of some tissues (e.g. blood
lymphocytes) results in severe neurological abnormalities in
newborns. The disease is characterized by excretion in the
urine of abnormally high amounts of a-ketoglutarate,
succinate, and fumarate. What enzyme deficiency would
lead to these symptoms? (Or at least tell me the substrate
and the product of the particular citric acid cycle step
involved.) Propose a possible way to solve this deficiency.
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2
. Fluoroacetate, prepared commercially for rat control, is also produced by a
South African plant. After entering the cell, fluoroacetate is converted to
fluoroacetyl-CoA in a reaction catalyzed by the enzyme acetate
thiokinase.
The toxic effect of fluoroacetate
was studied in an experiment using intact isolated rat heart. After the heart was
perfused (supplied with) with 0.22 mM fluoroacetate, the measured rate of
glucose uptake and glycolysis decreased, and glucose 6-phosphate and
fructose 6-phosphate accumulated. Examination of the citric acid cycle
intermediates revealed that their concentrations were below normal, except for
citrate, with a concentration 10 times higher than normal.
a) Where did the block in the in the citric acid cycle occur? What caused
citrate to accumulate and the other cycle intermediates to be depleted?
b) Fluoroacetyl CoA is enzymatically transformed in the citric acid cycle. The
transformed product is very similar to citrate. Why does this product block the
citric acid cycle? How might the effect of the transformed product be
overcome?
c) Why is fluoroacetic acid poisoning fatal?
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3. Explain why one NADH molecule is worth 3 ATP's.
4. Explain why one FADH2 molecule is worth 2 ATP's.
5. A total of 36 (or 38) molecules of ATP are derived from a
glucose molecule via glycolysis followed by aerobic respiration.
Describe where these ATP molecules come from.
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Cellular Respiration
Stage 1:
Glycolysis
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2007-2008
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
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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
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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

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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
Count the
carbons!
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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
Count the
carbons!
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O2
animals
some fungi
recycle
NADH
Pyruvate is a branching point
Pyruvate
O2
O2
fermentation
anaerobic
respiration
mitochondria
Krebs cycle
aerobic respiration
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Cellular Respiration
Stage 2 & 3:
Oxidation of Pyruvate
Krebs Cycle
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2006-2007
Cellular respiration
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Cellular Respiration
Stage 4:
Electron Transport Chain
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2006-2007
Cellular respiration
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Electron Transport Chain
Inner
mitochondrial
membrane
Intermembrane space
C
Q
NADH
dehydrogenase
cytochrome
bc complex
Mitochondrial matrix
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cytochrome c
oxidase complex
Remember the Electron Carriers?
Glycolysis
glucose
Krebs cycle
G3P
2 NADH
Time to
break open
the piggybank!
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8 NADH
2 FADH2
Electron Transport Chain
Building proton gradient!
NADH  NAD+ + H
e
p
intermembrane
space
H+
H+
H  e- + H+
C
e–
NADH H
FADH2
NAD+
NADH
dehydrogenase
inner
mitochondrial
membrane
e–
Q
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H+
e–
H
FAD
2H+ +
cytochrome
bc complex
1
2
O2
H2O
cytochrome c
oxidase complex
mitochondrial
matrix
What powers the proton (H+) pumps?…
Stripping H from Electron Carriers
 Electron carriers pass electrons & H+ to ETC
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H cleaved off NADH & FADH2
electrons stripped from H atoms  H+ (protons)
 electrons passed from one electron carrier to next in
mitochondrial membrane (ETC)
 flowing electrons = energy to do work

transport proteins in membrane pump H+ (protons)
across inner membrane to intermembrane space
H+
+
H
H+
TA-DA!!
Moving electrons
do the work!
+
H
H+
H+
+
H+ H+ H
+
H+ H H+
C
e–
NADH
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+
H
H+
Q
e–
FADH2
FAD
NAD+
NADH
dehydrogenase
e–
2H+
cytochrome
bc complex
+
1
2
O2
H2O
cytochrome c
oxidase complex
ADP
+ Pi
ATP
H+
But what “pulls” the
electrons down the ETC?
H 2O
O2
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electrons
flow downhill
to O2
oxidative phosphorylation
Electrons flow downhill
 Electrons move in steps from
carrier to carrier downhill to oxygen
each carrier more electronegative
 controlled oxidation
 controlled release of energy

make ATP
instead of
fire!
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“proton-motive” force
We did it!
 Set up a H+
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H+
H+
H+
gradient
Allow the protons
to flow through
ATP synthase
Synthesizes ATP
ADP + Pi  ATP
Are we
there yet?
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H+
H+
H+
H+
H+
ADP + Pi
ATP
H+
Chemiosmosis
 The diffusion of ions across a membrane
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build up of proton gradient just so H+ could flow
through ATP synthase enzyme to build ATP
Chemiosmosis
links the Electron
Transport Chain
to ATP synthesis
So that’s
the point!
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1961 | 1978
Peter Mitchell
 Proposed chemiosmotic hypothesis

revolutionary idea at the time
proton motive force
1920-1992
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Pyruvate from
cytoplasm
Inner
+
mitochondrial H
membrane
H+
Intermembrane
space
Electron
transport
C system
Q
NADH
Acetyl-CoA
1. Electrons are harvested
and carried to the
transport system.
NADH
Krebs
cycle
e-
e-
FADH2
e-
2. Electrons
provide energy
to pump
protons across
the membrane.
e-
H2O
3. Oxygen joins
with protons to
form water.
1 O
2 +2
2H+
O2
H+
CO2
ATP
Mitochondrial
matrix
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H+
ATP
ATP
4. Protons diffuse back in
down their concentration
gradient, driving the
synthesis of ATP.
H+
ATP
synthase
Cellular respiration
2 ATP
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+
2 ATP
+
~36 ATP
Summary of cellular respiration
C6H12O6 + 6O2
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 6CO2 + 6H2O + ~40 ATP
Where did the glucose come from?
Where did the O2 come from?
Where did the CO2 come from?
Where did the CO2 go?
Where did the H2O come from?
Where did the ATP come from?
What else is produced that is not listed
in this equation?
 Why do we breathe?
AP Biology
Taking it beyond…
 What is the final electron acceptor in
H+
H+
H+
C
Electron Transport Chain?
e–
NADH
O2
Q
e–
FADH2
FAD
NAD+
NADH
dehydrogenase
e–
2H+ +
cytochrome
bc complex
1
2
O2
H2O
cytochrome c
oxidase complex
 So what happens if O2 unavailable?
 ETC backs up
nothing to pull electrons down chain
 NADH & FADH2 can’t unload H

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 ATP production ceases
 cells run out of energy
 and you die!
What’s the
point?
The point
is to make
ATP!
ATP
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2006-2007
Do Now (Quiz)
 1. Which H+ ion has just passed through the inner mitochondrial
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membrane by diffusion?
A) hydrogen ion A
B) hydrogen ion B
C) hydrogen ion C
D) hydrogen ion D
E) hydrogen ion E
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Do Now (Quiz)
 As a scientist employed by the FDA, you've been asked to
sit on a panel to evaluate a pharmaceutical company's
application for approval of a new weight loss drug called
Fat Away. The company has submitted a report
summarizing the results of their animal and human testing.
In the report, it was noted that Fat Away works by affecting
the electron transport chain. It decreases the synthesis of
ATP by making the mitochondrial membrane permeable to
H+ which allows H+ to leak from the mitochondrial matrix to
the intermembrane space. This effect leads to weight loss.
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Do Now (Quiz)
 2. Fat Away prevents ATP from being made by
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A) blocking access of H+ to ATP synthetase.
B) glycolysis from occurring.
C) preventing the conversion of NADH to NAD+.
D) lowering body temperature.
E) slowing down the Krebs cycle.
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Do Now (Quiz)
 3. To obtain energy from starch and glycogen, the body
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must begin by
A) hydrolyzing the starch to glucose and the glycogen to
amino acids.
B) hydrolyzing both starch and glycogen to glucose.
C) converting both starch and glycogen to fatty acids.
D) removing nitrogen atoms from both molecules.
E) removing one glucose at a time with a condensation
reaction.
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Do Now (Quiz)
4. Which of the following statements regarding glycolysis is
false?
 A) Glycolysis is considered to be an ancient metabolic system
because it does not require oxygen.
 B) Glycolysis is considered to be an ancient metabolic system
because it is not located in a membrane-bound organelle.
 C) Glycolysis is considered to be an ancient metabolic system
because it occurs universally.
 D) Glycolysis is considered to be an ancient metabolic system
because it is the most efficient metabolic pathway for ATP
synthesis.
 E) Glycolysis is considered to be an ancient metabolic system
because glucose is the universal substrate for glycolysis.

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Do Now (Quiz)
 5. A child is born with a rare disease in which mitochondria
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are missing from skeletal muscle cells. However, the
muscles still function. Physicians find that
A) the muscles contain large amounts of lactate following
even mild physical exercise.
B) the muscles contain large amounts of carbon dioxide
following even mild physical exercise.
C) the muscles require extremely high levels of oxygen to
function.
D) the muscle cells cannot split glucose to pyruvate.
E) the muscles require extremely large amounts of carbon
dioxide to function.

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Do Now (Quiz)
 6. Which kind of metabolic poison would most directly
interfere with glycolysis?

A) an agent that reacts with oxygen and depletes its
concentration in the cell
B) an agent that binds to pyruvate and inactivates it
C) an agent that closely mimics the structure of glucose but
is not metabolized
D) an agent that reacts with NADH and oxidizes it to NAD+
E) an agent that blocks the passage of electrons along the
electron transport chain
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Do Now (Quiz)
 7. How does pyruvate enter the mitochondrion?

A) active transport
B) diffusion
C) facilitated diffusion
D) through a channel
E) through a pore
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Lab: Alcoholic Fermentation in Yeast
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Lorenzo’s Oil
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