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MA
KIN
G E
NER
GY:
CELLU
LA
R
RES
PIR
ATIO
N
WHERE WE LAST LEFT OFF:
**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 is the treasure chest catabolize glucose to produce ATP
C6H12O6 6O2 ATP 6H2O 6CO2+ + +
RESPIRATION = making ATP (& some heat)
by burning fuels in many small steps
CO2 + H2O + ATP (+ heat)
ATP
glucose
glucose + oxygen energy + water + carbondioxide
resp
irati
on
O2
+ heat
enzymes
ATP
Food digestion = bond breaking & electron movement (energy carrying)
Electron movementNOT alone → move as part of H atom p
e
+
H
+H
+ –loses e- gains e- oxidized reduced
oxidation reduction
C6H12O6 6O2 6CO2 6H2O ATP+ + +
oxidation
reductionH e-
HOW DO WE HARVEST ENERGY FROM FUELS?
Electron carriers move ele- by shuttling H atoms NAD+ NADH (reduced)FAD+2 FADH2 (reduced)
+ Hreduction
oxidation
P
O–
O–
O
–O
P
O–
O–
O
–O
CC
O
NH2
N+
H
adenine
ribose sugar
phosphates
NAD+
nicotinamideVitamin B3niacin
P
O–
O–
O
–O
P
O–
O–
O
–O
CC
O
NH2
N+
HNADH
carries electrons as a reduced molecule
reducing power!
H
Ele- Movement in Respiration
OVERVIEW OF CELLULAR RESPIRATION
4 metabolic stagesAnaerobic respiration (NO O2)
1. Glycolysisin cytosol
Aerobic respiration (O2)in mitochondria
2. Pyruvate oxidation3. Krebs cycle4. Electron transport chain
C6H12O6 6O2 ATP 6H2O 6CO2+ + + (+ heat)
1. GLYCOLYSIS
That’s not enoughATP for me!
“glyco – lysis” (splitting sugar)
Pathway observed in nearly ALL organisms
Speculated as one of oldest pathways, most fundamental
WHY?Inefficient
For every 1 glucose generate only 2 ATP
glucose pyruvate2x6C 3C
10 reactionsconvert
glucose (6C) to 2 pyruvate (3C)
produce: 4 ATP & 2 NADH
consumes:2 ATP
NET YIELD: 2 ATP & 2 NADH
glucoseC-C-C-C-C-C
fructose-1,6bPP-C-C-C-C-C-C-P
G3P x2C-C-C-P
Pyruvate x2C-C-C
OVERVIEW
G3P = glyceraldehyde-3-phosphate
ATP2
ADP2
ATP4
ADP4
NAD+2
2Pi
enzyme
enzyme
enzyme
enzyme
enzyme
enzyme
enzyme
2Pi
2H2 G3P x2
P~C-C-C-P
FEEDBACK CONTROL 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
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
glucosemore carbons to strip off = more
energy to harvest
O2
O2
O2
O2
O2
Is this enough to support life?
O2 present
Onto the Krebs Cycle!!!
ONWARD MITO!
intermembranespace inner
membrane
outermembrane
matrixcristae
MITOCHONDRIAL STRUCTURE REVIEW Double membrane
smooth outer membranehighly folded inner membrane
cristae intermembrane space
fluid-filled between membranesmatrix
inner fluid-filled spaceDNA, ribosomesenzymes
free in matrix & membrane-bound
mitochondrialDNA
Yield = 2C sugar + NADH + CO2
reduction
oxidation
Coenzyme APyruvate
Acetyl CoA
C-C-CC-CCO2
NAD+
2 x [ ]
Prepping for Krebs: formation of Acetyl CoA
pyruvate acetyl CoA + CO2
NAD
3C 2C 1C[2x ] Pyruvate enters matrix
3 step oxidation processreleases 2 CO2 reduces 2 NAD+ 2 NADH (moves e-)produces 2 acetyl CoA enters Krebs
cycle
Electron Carriers = Hydrogen Carriers
2. KREBS CYCLE aka Citric Acid Cycle
in mitochondrial matrix8 step pathway
each catalyzed by specific enzyme
step-wise catabolism of 6C citrate molecule (stripping out the carbons)
Appeared later than glycolysis – WHY?
1937 | 1953
Hans Krebs1900-1981
4C
6C
4C
4C
4C
2C
6C
5C
4C
CO2
CO2
citrate
acetyl CoACount the carbons!
3Cpyruvate
x2
oxidationof sugars
This happens twice for each glucose molecule
**Process regulated by + and – feedback control by [ATP]!!!**
4C
6C
4C
4C
4C
2C
6C
5C
4C
CO2
CO2
citrate
acetyl CoACount the electron carriers!
3Cpyruvate
reductionof electroncarriers
This happens twice for each glucose molecule x2 NADH
NADH
NADH
FADH2
ATP
•Fully oxidized
C6H12O6
CO2
•NET YIELD:(4 NADH) x 2(1 ATP) x 2(1 FADH2) x 2
8 NADH2 ATP
2 FADH2
How’s our savings?
LET’S RECAP… Glycolysis 2 ATP Kreb’s cycle 2 ATP
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
I need a lot
more ATP!
3. THE ETC!!!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!
THE PLAYERS…
Intermembrane space
Mitochondrial matrix
Q
C
NADH dehydrogenase
cytochromebc complex
cytochrome coxidase complex
Innermitochondrialmembrane
intermembranespace
mitochondrialmatrix
innermitochondrialmembrane
NAD+
Q
C
NADH H2O
H+
e–
2H+ + O2
H+H+
e–
FADH2
12
NADH dehydrogenase
cytochromebc complex
cytochrome coxidase complex
FAD
e–
H
H e- + H+
NADH NAD+ + H
H
pe
Building proton gradient!
What powers the proton (H+) pumps?…
Let’s Follow the Chain…
Ele- move in steps from carrier to carrier downhill to oxygeneach carrier more electronegativecontrolled oxidationcontrolled release of energy
Electrons Flow Downhill
H+
ADP + Pi
H+H+
H+
H+ H+
H+H+H+
SO, WHAT’S THE POINT??
Set up H+
gradient Allow protons
to flow through ATP synthase
Synthesize ATP
ADP + Pi ATP
CHEMIOSMOSIS!!!
Energy Conversion**The Rules: NADH = 3 ATP
FADH2 = 2 ATP
Glycolysis – 2 NADH
Conversion to – 2 NADH Acetyl CoA
Krebs cycle - 6 NADH 2 FADH2
ETC
6 ATP
6 ATP
18 ATP + 4 ATP = 22 ATP
34 ATP!!!
SUMMING IT UP!
2 ATP 2 ATP ~34 ATP+ +
~40 ATP
BEYOND SUGARS…
amino group = Waste, excreted as ammonia, urea, or uric acid
NH
HC—OH
||OH
|—C—|
R
waste glycolysisKrebs cycle
proteins amino acidshydrolysis
2C sugar = carbon skeleton = enters glycolysis or Krebs cycle
fatty acids 2C acetyl acetyl Krebs groups coA cycle
3C glycerol
entersglycolysisas G3P
enterKrebs cycleas acetyl CoA
2C fatty acids
fats glycerol + fatty acidshydrolysis
glycerol (3C) G3P glycolysis
Digestioncarbohydrates,
fats & proteinsall catabolized
through same pathways
enter at different points
cell extracts energy from every source
ENERGY FROM ALL AVENUES!
Why waste? Enough energy? Build stuff!!!
points in glycolysis & Krebs cycle used as link to pathways for synthesisrun pathways
“backwards”have extra fuel,
build fat!
Krebs cycleintermediaries amino
acids
pyruvate glucose
acetyl CoA fatty acids
What happens the absence of oxygen?
Pyruvate
O2
O2
aerobic respirationmitochondriaKrebs cycle
anaerobicrespirationfermentation
Dead end process ~12% ethanol, kills cells can’t reverse reaction
Alcohol Fermentation
Reversible process if O2 becomes available, lactate
converted to pyruvate by the liver
Lactic Acid Fermentation
ANAEROBIC FERMENATION: WHAT’S THE POINT???
recycleNADH
Bacteria, yeast
Animals, some fungi
1C3C 2Cpyruvate ethanol + CO2
pyruvate lactic acid3C 3C
beer, wine, bread
cheese, anaerobic exercise (no O2)
NADH NAD+
NADH NAD+
back to glycolysis
back to glycolysis
Commercial Uses…
