Chapter 9. Cellular Respiration STAGE 1: Glycolysis
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Transcript Chapter 9. Cellular Respiration STAGE 1: Glycolysis
Cellular Respiration
Stage 1:
Glycolysis
AP Biology
2007-2008
What’s the
point?
The point
is to make
ATP!
ATP
AP Biology
2007-2008
Glycolysis
Breaking down glucose
“glyco – lysis” (splitting sugar)
glucose pyruvate
2x 3C
6C
In the
cytosol?
Why does
that make
evolutionary
sense?
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
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occurs in cytosol
Evolutionary perspective
Prokaryotes
first cells had no organelles
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
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ALL cells still utilize glycolysis
You mean
we’re related?
Do I have to invite
them over for
the holidays?
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:
2Pi
enzyme
2 ATP & 2 NADH
DHAP = dihydroxyacetone phosphate
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G3P
= glyceraldehyde-3-phosphate
pyruvate
C-C-C
2 NAD+
2
4 ADP
4 ATP
Glycolysis summary
endergonic
invest some ATP
ENERGY INVESTMENT
ENERGY PAYOFF
G3P
C-C-C-P
4ATP
exergonic
harvest a little
ATP & a little NADH
like $$
in the
bank
NET YIELD
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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+
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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)
G3P
C-C-C-P
Energy Harvest
NAD+
NADH production
ADP
oxidize sugar
ATP
NAD+
Pi
6
NAD+
NADH
G3P donates H
reduce NAD+
Pi
NADH
7
phosphoglycerate
kinase
3-Phosphoglycerate
(3PG)
NADH
ADP
ATP
3-Phosphoglycerate
(3PG)
8
phosphoglyceromutase
G3P pyruvate
PEP sugar donates P
ADP ATP
Phosphoenolpyruvate
(PEP)
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Payola!
Finally some
ATP!
ADP
2-Phosphoglycerate
(2PG)
9
enolase
H2O
O P
C O
H C O
CH2OH
P
OH2O
Phosphoenolpyruvate
(PEP)
10
pyruvate kinase
ADP
ATP
Pyruvate
C
C
O
O
CH2
OC
ATP
Pyruvate
CHOH
CH2
O-
ATP production
2-Phosphoglycerate
(2PG)
OC
O
C O
CH3
P
Substrate-level Phosphorylation
In the last steps of glycolysis, where did
the P come from to make ATP?
9
the sugar substrateH O(PEP) enolase
OH2O
2
P is transferred
from PEP to ADP
kinase enzyme
ADP ATP
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Phosphoenolpyruvate
(PEP)
ADP
Phosphoenolpyruvate
(PEP)
10
pyruvate kinase
Pyruvate
I get it!
The PO4 came
directly from
the substrate!
Pyruvate
C
CH2
O
O
OC
ATP
ATP
ATP
ADP
C
O
C O
CH3
P
Energy accounting of glycolysis
2 ATP
2 ADP
glucose pyruvate
2x 3C
6C
4 ADP
4 ATP
Net gain = 2 ATP
some energy investment (-2 ATP)
small energy return (+4 ATP)
1 6C sugar 2 3C sugars
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All that work!
And that’s all
I get?
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
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O2
glucose pyruvate
2x 3C
6C
Hard way
to make
a living!
We can’t stop there!
G3P
DHAP
NAD+
Pi
NAD+
Pi
NADH
NADH
1,3-BPG
1,3-BPG
Glycolysis
glucose + 2ADP + 2Pi + 2 NAD+ 2 pyruvate + 2ATP + 2NADH
Going to run out of NAD+
without regenerating NAD+,
energy production would stop!
another molecule must accept
H from NADH
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recycle
NADH
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)
which path you
use depends on
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who
you are…
Krebs
cycle
ethanol
Fermentation (anaerobic)
Bacteria, yeast
pyruvate ethanol + CO2
3C
NADH
2C
1C
NAD+
beer, wine, bread
to glycolysis
Animals, some fungi
pyruvate lactic acid
3C
NADH
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3C
NAD+to glycolysis
cheese, anaerobic exercise (no O2)
Alcohol Fermentation
pyruvate ethanol + CO2
3C
NADH
2C
NAD+
Dead end process
at ~12% ethanol,
kills yeast
can’t reverse the
reaction
Count the
carbons!
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1C
bacteria
yeast
animals
Lactic Acid Fermentation
pyruvate lactic acid
3C
NADH
3C
NAD+
Reversible process
once O2 is available,
lactate is converted
back to pyruvate by
the liver
Count the
carbons!
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O2
Pyruvate is a branching point
Pyruvate
O2
O2
fermentation
anaerobic
respiration
mitochondria
Kreb’s cycle
aerobic respiration
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What’s the
point?
The point
is to make
ATP!
ATP
AP Biology
2007-2008
H+
And how do we do that? H
+
H+
H+
H+
H+
H+
H+
ATP synthase
set up a H+ gradient
allow H+ to flow
through ATP synthase
powers bonding
of Pi to ADP
ADP + P
ADP + Pi ATP
ATP
H+
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But…
Have we done that yet?
NO!
There’s still more
to my story!
Any Questions?
AP Biology
2007-2008