1. Cellular Respiration Harvesting Chemical Energy
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2. Chemical Recycling
The products of respiration are the raw materials for photosynthesis.
Photosynthesis produces glucose and oxygen, the raw materials for cellular respiration.
Chemical elements essential for life are recycled, but energy is not.
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3. ATP The Point is to Make ATP! What’s the point?
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4. Harvesting stored energy
Energy is stored in organic molecules
heterotrophs eat food
digest organic molecules
serve as raw materials for building & fuels for energy
controlled release of energy
series of step-by-step enzyme-controlled reactions (metabolic pathway)
We eat to take in the fuels to make ATP which will then be used to help us build biomolecules and grow and move and… live!
heterotrophs = “fed by others”
vs.
autotrophs = “self-feeders”
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5. Harvesting energy stored in glucose
Glucose is the model
breakdown of glucose to produce ATP
glucose + oxygen  carbon + water + energy
dioxide
+ heat
respiration
C6H12O6
6O2
6CO2
6H2O
ATP  +
Movement of hydrogen atoms from glucose to water
fuel (carbohydrates)
combustion = making heat energy by burning fuels in one step
respiration = making ATP (& less heat) by burning fuels in many small steps
ATP
glucose
CO2 + H2O + heat
CO2 + H2O + ATP (+ heat)
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6. Moving electrons in respiration
Electron carriers move electrons by shuttling H atoms around
There are 2 in Cellular respiration
NAD+ (NADH is reduced form
FAD+2 (FADH2 is reduced form)
reducing power!
How efficient!
Build once, use many ways
Nicotinamide adenine dinucleotide (NAD) — and its relative nicotinamide adenine dinucleotide phosphate (NADP) which you will meet in photosynthesis — are two of the most important coenzymes in the cell.
In cells, most oxidations are accomplished by the removal of hydrogen atoms. Both of these coenzymes play crucial roles in this.
Nicotinamide is also known as Vitamin B3 is believed to cause improvements in energy production due to its role as a precursor of NAD (nicotinamide adenosine dinucleotide), an important molecule involved in energy metabolism. Increasing nicotinamide concentrations increase the available NAD molecules that can take part in energy metabolism, thus increasing the amount of energy available in the cell.
Vitamin B3 can be found in various meats, peanuts, and sunflower seeds. Nicotinamide is the biologically active form of niacin (also known as nicotinic acid).
FAD is built from riboflavin — also known as Vitamin B2. Riboflavin is a water-soluble vitamin that is found naturally in organ meats (liver, kidney, and heart) and certain plants such as almonds, mushrooms, whole grain, soybeans, and green leafy vegetables. FAD is a coenzyme critical for the metabolism of carbohydrates, fats, and proteins into energy.
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7. Overview of cellular respiration
3 Stages
1. Glycolysis
2. Krebs cycle
3. Electron transport chain
C6H12O6
6O2
6CO2
6H2O
ATP  +
(+ heat)
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8. ATP The Point is to Make ATP! What’s the point?
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9. Glycolysis - The Gateway
Breaking down glucose
“glyco – lysis” (splitting sugar)
occurs in cytosol
Anaerobic (Does not require oxygen)
inefficient production of energy
glucose      pyruvate 2x 6C 3C
Why does it make sense that this happens in the cytosol?
Who evolved first?
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10. Glycolysis summary Energy Investment (endergonic) invest 2 ATP
Energy Yielding (exergonic)
harvest 4 ATP & 2 NADH
Glucose is a stable molecule it needs an activation energy to break it apart.
phosphorylate it = Pi comes from ATP.
make NADH & put it in the bank for later.
like $$ in the bank
Net Result
2 ATP
2 NADH
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11. Pyruvate is a branching point
Anaerobic
respiration
(fermentation) -
Other organic
electron acceptor
Aerobic
Respiration -
Oxygen accepts electrons
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12. Fermentation: Recycling NAD+?
Fermentation: The recycling of NAD+ using an organic electron acceptor instead of oxygen
aerobic respiration
to Krebs Cycle & Electron Transport Chain in mitochondria
anaerobic respiration
ethanol fermentation
lactic acid fermentation O2 O2
NADH
which path you use depends on who you are…
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13. Fermentation (anaerobic)
Alcoholic: Bacteria, yeast 1C 3C 2C
pyruvate  ethanol + CO2
NADH
NAD+
to glycolysis
Lactic Acid: Bacteria, fungi, human muscles
Count the carbons!!
Lactic acid is not a dead end like ethanol. Once you have O2 again, lactate is converted back to pyruvate by the liver and fed to the Kreb’s cycle.
pyruvate  lactic acid 3C
NADH
NAD+
to glycolysis
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14. Alcohol Fermentation pyruvate  ethanol + CO2 Dead end process
bacteria yeast
Alcohol Fermentation 1C 3C 2C
pyruvate  ethanol + CO2
NADH
NAD+
Dead end process
Makes our beer, wine, cheeses and other food products!
Count the carbons!
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15. Lactic Acid Fermentation
Bacteria
fungi
Lactic Acid Fermentation O2
pyruvate  lactic acid 3C 
NADH
NAD+
Reversible process
once O2 is available, lactate is converted to pyruvate by liver
Count the carbons!
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16. ATP The Point is to Make ATP! What’s the point?
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17. Pyruvate is a branching point
Anaerobic
respiration
(fermentation) -
Other organic
electron acceptor
Aerobic
Respiration -
Oxygen accepts electrons
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18. Cellular respiration
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19. Formation of Acetyl CoA
The link between glycolysis and the Krebs Cycle is the change of of pyruvate to acetyl CoA.
Pyruvate (3C) has to be “shortened” by one carbon so that in can enter the mitochondria
It must enter the cycle as a 2 carbon molecule, Acetyl-CoA (2C).
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20. Formation of Acetyl CoA
Releases 2 CO2 (count the carbons!)
Makes 2 NADH
Sometimes creates 2 ATP.
Acetyl CoA enters Krebs cycle
where does CO2 go? [ 2x ]
pyruvate    acetyl CoA + CO2 3C
NAD
NADH 2C 1C
CO2 is fully oxidized carbon == can’t get any more energy out it
CH4 is a fully reduced carbon == good fuel!!!
Take a deep breath… now exhale!
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21. Krebs cycle 1937 | 1953 aka Citric Acid Cycle Happens in mitochondria
Aerobic
5 step pathway
each catalyzed by specific enzyme
digestion of 6C molecule
Hans Krebs
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22. Count the carbons! x2 3C 2C 4C 6C 4C 6C 5C 4C 4C 4C
pyruvate 3C 2C
acetyl CoA
citrate 4C 6C x2 4C 6C
This happens twice for each glucose molecule
oxidation of sugars
CO2
A 2 carbon sugar went into the Krebs cycle and was taken apart completely. Two CO2 molecules were produced from that 2 carbon sugar. Glucose has now been fully oxidized!
But where’s all the ATP??? 5C 4C
CO2 4C 4C
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23. Kreb’s Cycle
Krebs cycle produces large quantities of electron carriers
NADH
FADH2
These go on to Electron Transport Chain
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24. Energy accounting of Krebs cycle
3 NAD + 1 FAD
3 NADH + 1 FADH2 2x
pyruvate          2CO2
1 ADP
1 ATP 3C
ATP
Net gain = 2 ATP
= 6 NADH + 2 FADH2
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25. So why the Krebs cycle? If the yield is only 2 ATP, then why?
value of NADH & FADH2
electron carriers carry energy in the form of excited electrons!!!
like $$ in the bank
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26. ATP The Point is to Make ATP! What’s the point?
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27. ATP accounting so far… There’s got to be a better way!
Glycolysis  2 ATP
Kreb’s cycle  2 ATP
Acetyl CoA  ~ 2 ATP
Life takes a lot of energy to run, need to extract more energy than 4 ATP!
There’s got to be a better way!
What’s the point?
A working muscle recycles over 10 million ATPs per second
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28. That sounds more like it!
There is a better way!
Electron Transport Chain
series of molecules built into inner mitochondrial membrane
transport proteins
transport of electrons down ETC linked to ATP synthesis
yields double-digit ATP!!!!!!!!!!!!!!!!
only in presence of O2 (aerobic) O2
That sounds more like it!
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29. Oooooh! Form fits function!
Mitochondria
Matrix
central fluid-filled space
Double membrane
outer membrane
inner membrane
highly folded cristae
fluid-filled space between membranes = intermembrane space
Oooooh! Form fits function!
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30. Time to break open the bank!
Remember the NADH?
Krebs cycle
Glycolysis
G3P
6 NADH
2 FADH2
4 NADH
Time to break open the bank!
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31. Electron Transport Chain
Electron carrier pass electrons to ETC
electrons passed from one electron carrier to next in mitochondrial membrane (ETC)
transport proteins in membrane pump H+ across inner membrane
Oxidation refers to the loss of electrons to any electron acceptor, not just to oxygen.
Uses exergonic flow of electrons through ETC to pump H+ across membrane. H+
TA-DA!!
NAD+ Q C
NADH
H2O H+ e–
2H+ + O2
FADH2 1 2
NADH dehydrogenase
bc1 complex
Cytochrome oxidase complex
FAD
ADP + Pi
ATP
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32. “proton-motive” force
We did it! H+
ADP + Pi
Set up a H+ gradient
Allow the H+ to flow through ATP synthase
Synthesizes ATP
ADP + Pi  ATP
ATP
Are we there yet?
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33. Electron Transport Chain
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34. Cellular respiration + + + ~38 ATP 2 ATP ~2 ATP 2 ATP ~34 ATP
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35. Summary of cellular respiration
C6H12O6
6O2
6CO2
6H2O
~38 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?
Where did the glucose come from?
from food eaten
Where did the O2 come from?
breathed in
Where did the CO2 come from?
oxidized carbons cleaved off of the sugars
Where did the CO2 go?
exhaled
Where did the H2O come from?
from O2 after it accepts electrons in ETC
Where did the ATP come from?
mostly from ETC
What else is produced that is not listed in this equation?
NAD, FAD, heat!
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