1. Cellular Respiration
Stage 1:
Glycolysis
AP Biology 2007-2008

2. What’s the
point?
The point
is to make
ATP!
ATP
AP Biology 2007-2008

3. Glycolysis
 Breaking down glucose
 “glyco – lysis” (splitting sugar) In the
cytosol?
glucose → → → → → pyruvate Why does
that make
6C 2x 3C 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
 occurs in cytosol That’s not enough
AP Biology ATP for me!

4. Evolutionary perspective
Enzymes
 Prokaryotes of glycolysis are
 first cells had no organelles “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
 ALL cells still utilize glycolysis
You mean
we’re related?
Do I have to invite
them over for
AP Biology the holidays?

5. glucose
Overview C-C-C-C-C-C
enzyme 2 ATP
10 reactions
enzyme 2 ADP
 convert fructose-1,6bP
glucose (6C) to P-C-C-C-C-C-C-P
2 pyruvate (3C) enzyme enzyme
enzyme
 produces: DHAP G3P
4 ATP & 2 NADH P-C-C-C C-C-C-P 2 NAD+
2H
 consumes: 2Pi enzyme
2
2 ATP enzyme
 net yield: 2Pi 4 ADP
enzyme
2 ATP & 2 NADH
pyruvate 4 ATP
DHAP = dihydroxyacetone phosphate
G3P Biology
AP
= glyceraldehyde-3-phosphate C-C-C

6. Glycolysis summary
ENERGY INVESTMENT endergonic
invest some ATP
-2 ATP
G3P
ENERGY PAYOFF C-C-C-P exergonic
harvest a little
4 ATP
ATP & a little NADH
like $$
in the
bank
NET YIELD net yield
2 ATP
AP Biology 2 NADH

7. 1st half of glycolysis (5 reactions)
CH2OH
Glucose “priming” Glucose
1
O
ATP
hexokinase
 get glucose ready ADP CH2 O P
O
to split Glucose 6-phosphate
2
 phosphorylate phosphoglucose
CH2 O P
glucose isomerase
O CH2OH
Fructose 6-phosphate
 molecular 3
ATP
rearrangement phosphofructokinase
P O CH2 CH2 O P
ADP O
 split destabilized Fructose 1,6-bisphosphate
glucose 4,5 aldolase
H
P O CH2 isomerase
C O Dihydroxyacetone C O
Glyceraldehyde 3
CHOH
CH2OH phosphate -phosphate (G3P)
CH2 O P
NAD+ Pi 6 Pi NAD+
NADH glyceraldehyde NADH
3-phosphate P O O
dehydrogenase
1,3-Bisphosphoglycerate 1,3-Bisphosphoglycerate CHOH
AP Biology
(BPG) (BPG) CH2 O P

8. 2nd half of glycolysis (5 reactions)
DHAP G3P
Energy Harvest P-C-C-C C-C-C-P
NAD+ Pi Pi NAD+
6
 NADH production NADH NADH
 G3P donates H ADP 7 ADP
phosphoglycerate O-
 oxidizes the sugar ATP
kinase ATP C
 reduces NAD+ 3-Phosphoglycerate 3-Phosphoglycerate CHOH
(3PG) (3PG)
 NAD+ → NADH 8
CH2 O P
O-
 ATP production phosphoglycero-
mutase C O
 G3P → → → pyruvate 2-Phosphoglycerate 2-Phosphoglycerate H C O P
(2PG) (2PG) CH2OH
 PEP sugar donates P
9 O-
 “substrate level H2O enolase H2O
C O
phosphorylation” O
C P
 ADP → ATP Phosphoenolpyruvate Phosphoenolpyruvate
CH2
(PEP) (PEP)
10 O-
ADP ADP
pyruvate kinase
Payola! ATP
C O
ATP
Finally some C O
AP Biology ATP! Pyruvate Pyruvate CH3

9. Substrate-level Phosphorylation
 In the last steps of glycolysis, where did
the P come from to make ATP?
 the sugar substrate O
H
(PEP) enolase
2
9
H2O
O-
C O
O
P is transferred Phosphoenolpyruvate
(PEP)
Phosphoenolpyruvate
(PEP)
C
CH2
P
from PEP to ADP ADP 10 ADP
O-
kinase enzyme ATP
pyruvate kinase
ATP
C O
C O
ADP → ATP Pyruvate Pyruvate CH3
ATP
I get it!
The Pi came
directly from
the substrate!
AP Biology

10. Energy accounting of glycolysis
2 ATP 2 ADP
glucose → → → → →
pyruvate
6C 2x 3C
4 ADP 4 ATP All that work!
And that’s all
I get?
2 NAD+ 2 But
glucose has
so much more
 Net gain = 2 ATP + 2 NADH to give!
 some energy investment (-2 ATP)
 small energy return (4 ATP + 2 NADH)
 1 6C sugar → 2 3C sugars
AP Biology

11. 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 glucose → → → → pyruvate
6C 2x 3C
O2
Hard way
O2 to make
a living!
AP Biology
O2

12. But can’t stop there! DHAP G3P
NAD+ Pi Pi NAD+
raw materials → products NADH
NAD+ Pi 6 Pi NADH
NAD+
NADH 1,3-BPG 1,3-BPG NADH
ADP 7 ADP
Glycolysis ATP ATP
3-Phosphoglycerate 3-Phosphoglycerate
(3PG) (3PG)
glucose + 2ADP + 2Pi + 2 NAD+ → 2 pyruvate + 2ATP + 2NADH
8
2-Phosphoglycerate 2-Phosphoglycerate
 Going to run out of NAD+ (2PG)
9
(2PG)
H2O H2O
 without regenerating NAD+,
energy production would stop! Phosphoenolpyruvate Phosphoenolpyruvate
(PEP) (PEP)
 another molecule must accept HADP 10 ADP
from NADH ATP ATP
 so Pyruvate Pyruvate
AP Biology NAD+ is freed up for another round

13. How is NADH recycled to NAD+?
with oxygen without oxygen
Another molecule aerobic respiration anaerobic respiration
must accept H pyruvate
“fermentation”
from NADH
H2O NAD+
CO2
O2 NADH NADH acetaldehyde
recycle acetyl-CoA NADH
NAD+
NADH
lactate NAD+
lactic acid
fermentation
which path you Krebs
ethanol
use depends on cycle
alcohol
who you are…
AP Biology fermentation

14. Fermentation (anaerobic)
 Bacteria, yeast
pyruvate → ethanol + CO2
3C 2C 1C
NADH NAD+
back to glycolysis→→
 beer, wine, bread
 Animals, some fungi
pyruvate → lactic acid
3C 3C
NADH NADback to glycolysis→→
+

AP Biology cheese, anaerobic exercise (no O2)

15. bacteria
Alcohol Fermentation yeast
recycle
pyruvate → ethanol + CO2 NADH
3C 2C 1C
NADH NAD+ back to glycolysis→→
 Dead end process
 at ~12% ethanol,
kills yeast
 can’t reverse the
reaction
Count the
carbons!
AP Biology

16. animals
some fungi
Lactic Acid Fermentation recycle
O2
pyruvate → lactic acid
→
NADH
3C 3C
NADH NAD+ back to glycolysis→→
 Reversible process
 once O2 is available,
lactate is converted
back to pyruvate by
the liver
Count the
carbons!
AP Biology

17. Pyruvate is a branching point
Pyruvate
O2 O2
fermentation
anaerobic
respiration
mitochondria
Krebs cycle
aerobic respiration
AP Biology

18. What’s the
point?
The point
is to make
ATP!
ATP
AP Biology 2007-2008

19. H+
H+ H+ H+
And how do we do that? 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+
But… Have we done that yet?
AP Biology

20. NO!
There’s still more
to my story!
Any Questions?
AP Biology 2007-2008