Download O 2 - Madison Public Schools

**Glucose made as a byproduct of
photosynthetic reactions
Harvesting stored energy…
 Energy

stored in organic molecules
carbohydrates, fats, proteins
 Heterotrophs

eat food
digestive results…
 raw materials for synthesis
 fuels for energy
 controlled release of energy
 “burning” fuels occurs in series of
step-by-step enzyme-controlled reactions
 Glucose
respiration
 catabolize
is the treasure chest
glucose to produce ATP
glucose + oxygen  energy + water + carbon
dioxide
C6H12O6 + 6O2
 ATP + 6H2O + 6CO2 + heat
RESPIRATION = making ATP (& some heat)
by burning fuels in many small steps
ATP
ATP
O2
CO2 + H2O + ATP (+ heat)
glucose
enzymes
 Food
digestion = bond breaking & electron movement
(energy carrying)
 Electron movement
e

NOT alone → move as part of H atom
loses e-
gains e-
p
oxidized
+
+
reduced
+
–
H
oxidation
reduction
H
oxidation
C6H12O6 + 6O2
H e-
 6CO2 + 6H2O + ATP
reduction
Ele- Movement in Respiration
 Electron
carriers move ele- by shuttling H
atoms
NAD+  NADH (reduced)
 FAD+2  FADH2 (reduced)

NAD+
nicotinamide
Vitamin B3
niacin
NADH
O
H
C
N+
O–
O– P
reducing power!
–O
+
NH2
H
reduction
oxidation
N+
O–
O– P
O
O–
O– P
O–
O– P
adenine
–O
O
ribose sugar
O
C
O
phosphates
H H
carries electrons as a
reduced molecule
O
–O
–O
NH
4
metabolic stages
Anaerobic respiration (NO O2)
1. Glycolysis
 in cytosol
 Aerobic respiration (O2)
 in mitochondria
2. Pyruvate oxidation
3. Krebs cycle
4. Electron transport chain

C6H12O6 + 6O2
 ATP
+ 6H2O + 6CO2 (+ heat)
 “glyco
– lysis” (splitting sugar)
glucose      pyruvate
2x 3C
6C

Pathway observed in nearly ALL organisms
Speculated as one of oldest pathways, most
fundamental
 WHY?


Inefficient

For every 1 glucose generate only 2 ATP
That’s not enough
ATP for me!
glucose
C-C-C-C-C-C
10 reactions
 convert
glucose (6C) to
2 pyruvate (3C)
 produce:
4 ATP & 2 NADH
 consumes:
2 ATP
 NET YIELD:
2 ATP & 2 NADH
2
enzyme
2
enzyme
ATP
ADP
fructose-1,6bP
P-C-C-C-C-C-C-P
G3P = glyceraldehyde-3-phosphate
enzyme
enzyme
G3P x2
C-C-C-P
2Pi enzyme
enzyme
enzyme
2H
2
NAD+
2
G3P x2
P~C-C-C-P
2Pi
4
Pyruvate x2 4
C-C-C
ADP
ATP
 Why

use excess when its not needed?
[ATP] activates/inactivates phosphofructokinase
Enzyme used to make
1,6 fructose bisphosphate


Allosteric regulation!!!

2 active sites

1. forms 1,6 fructose bisphosphate
2. conformation change, inactivate

Is this enough to support life?
 Not

a lot of energy…
for 1 billon years+ life on Earth survived this
way
 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 present
O2
O2
O2
Onto the Krebs
Cycle!!!
 Double


smooth outer membrane
highly folded inner membrane





membrane
cristae
intermembrane space
 fluid-filled between membranes
matrix
 inner fluid-filled space
DNA, ribosomes
enzymes
intermembrane
 free in matrix & membrane-boundspace
outer
membrane
inner
membrane
cristae
matrix
mitochondrial
DNA
Prepping for Krebs:
formation of Acetyl CoA
NAD+
Pyruvate
C-C-C
2x
reduction
Coenzyme A
Acetyl CoA
CO2
C-C
oxidation
[ Yield = 2C sugar + NADH + CO ]
2
Electron Carriers = Hydrogen Carriers
 Pyruvate
[
enters matrix
2x pyruvate    acetyl CoA + CO2
3C
2C
1C
NAD
3 step oxidation process
 releases 2 CO2
 reduces 2 NAD+  2 NADH (moves e-)
 produces 2 acetyl CoA  enters Krebs cycle

]
1937 | 1953
 aka
 in
8
Citric Acid Cycle
mitochondrial matrix
step pathway
each catalyzed by specific enzyme
 step-wise catabolism of 6C citrate
molecule (stripping out the carbons)

 Appeared
later than glycolysis – WHY?
Hans Krebs
1900-1981
Count the carbons!
pyruvate
3C
2C
acetyl CoA
6C
4C
This happens
twice for each
glucose molecule
4C
by + and –
feedback control
by [ATP]!!!**
6C
oxidation
of sugars
CO2
x2
4C
**Process regulated
4C
citrate
5C
4C
CO2
Count the electron carriers!
pyruvate
3C
4C
acetyl CoA
6C
4C
NADH
This happens
twice for each
glucose molecule
2C
6C
reduction
of electron
carriers
CO2
x2
4C
FADH2
4C
NADH
5C
4C
ATP
citrate
CO2
NADH
How’s our savings?
•Fully oxidized
C6H12O6

CO2
•NET YIELD:
(4 NADH) x 2
(1 ATP) x 2
(1 FADH2) x 2
8 NADH
2 ATP
2 FADH2
 2 ATP
 Kreb’s cycle  2 ATP
 Glycolysis
 Life
takes a lot of energy to
run, need to extract more
energy than 4 ATP!
 Fun
Fact!!!
A working muscle recycles over
10 million ATPs per second
 Proteins
built into
inner mitochondrial membrane
along cristae
 transport proteins & enzymes

 In
presence of O2
 Ele-
shuttled (by NADH &
FADH2)down ETC pump H+ to
create H+ gradient →
chemiosmosis!!!
 yields ~36 ATP from 1 glucose!
Inner
mitochondrial
membrane
Intermembrane space
C
Q
NADH
dehydrogenase
cytochrome
bc complex
Mitochondrial matrix
cytochrome c
oxidase complex
Let’s Follow the Chain…
Building proton gradient!
NADH  NAD+ + H
e
p
intermembrane
space
H+
H+
H  e- + H+
H+
C
Q
e–
NADH H
e–
e–
H
FADH2
FAD
2H+ +
NAD+
NADH
dehydrogenase
inner
mitochondrial
membrane
cytochrome
bc complex
1
O2
H 2O
2
cytochrome c
oxidase complex
mitochondrial
matrix
What powers the proton (H+) pumps?…
Electrons Flow Downhill
 Ele-
move in steps from
carrier to carrier downhill to oxygen
 each carrier more electronegative
 controlled oxidation
 controlled release of energy
 Set
H+
H+ gradient
up
 Allow protons
to flow through ATP
synthase
 Synthesize ATP
H+
H+
H+
H+
H+
H+
H+
ADP + Pi  ATP
ADP + Pi
CHEMIOSMOSIS!!!
H+
Energy Conversion
**The Rules: NADH = 3 ATP
FADH2 = 2 ATP
 Glycolysis
–
2 NADH
6 ATP
 Conversion
to – 2 NADH
6 ATP
Acetyl CoA
 Krebs
 ETC
cycle - 6 NADH
2 FADH2
34 ATP!!!
18 ATP +
4 ATP =
22 ATP
2 ATP
+
2 ATP
+
~34 ATP
proteins      amino acids
hydrolysis
waste
O
H
H |
||
C—OH
N —C—
H |
R
amino group =
Waste, excreted as
ammonia, urea, or
uric acid
glycolysis
Krebs cycle
2C sugar =
carbon skeleton =
enters glycolysis or
Krebs cycle
fats  
   glycerol + fatty acids
hydrolysis
glycerol (3C)   G3P   glycolysis
fatty acids  2C acetyl  acetyl  Krebs
groups
coA
cycle
3C glycerol
enters
glycolysis
as G3P
2C fatty acids
enter
Krebs cycle
as acetyl CoA
 Digestion
 carbohydrates,
fats &
proteins
 all catabolized
through same
pathways
 enter at different
points
 cell extracts energy
from every source
Why waste? Enough energy?
Build stuff!!!
 points
in glycolysis &
Krebs cycle used as
link to pathways for
synthesis
 run pathways
“backwards”
 have extra fuel,
build fat!
pyruvate
  glucose
Krebs cycle
intermediaries
acetyl CoA

amino
acids
  fatty acids
What happens the
absence of oxygen?
Pyruvate
O2
O2
anaerobic
respiration
fermentation
aerobic respiration
mitochondria
Krebs cycle
Alcohol Fermentation
Dead end process
 ~12% ethanol, kills cells
 can’t reverse reaction
Lactic Acid Fermentation
Reversible process
 if O2 becomes available, lactate converted to
pyruvate by the liver
recycle
NADH
Commercial Uses…
 Bacteria,
yeast
pyruvate  ethanol + CO2
3C
NADH
2C
NAD+
 beer, wine, bread
 Animals,
1C
back to glycolysis
some fungi
pyruvate  lactic acid
3C
NADH
3C
NAD+back to glycolysis
 cheese, anaerobic exercise (no O2)


ETC
ATP Synthase