• http://chatt.hdsb.ca/~duncand/FOV1-000D8CF8/FOV1-000E9546/FOV1-000E954C/Krebs%20Cycle.pdf
Cellular Respiration
The Mitochondria
The MitochondriaWhat
characteristics do you notice about
the mitochondria?
What features does it have?
Mitochondrial Structure
Mitochondrion vs. ChloroplastWhat do they have in common?
What appears different?
• Both have their own DNA
• Both are small like prokaryotes
• Both make energy
Why are mitochondria important?
• All cells require energy in the form of _______.
• Mitochondria are the “powerhouses” that supply that energy by performing cellular respiration
What is Cellular Respiration?• Cellular Respiration is the
process that releases energy by breaking down food molecules in the presence of oxygen.
• all eukaryotic cells*
• Takes energy from food (glucose) and turns it into a form cells can use (ATP)*.
O2CO2
Lungs
CO2 O2Bloodstream
BREATHING
CELLULAR RESPIRATION
Cell Respiration Equation
6O2 + C6H12O2 6CO2 + 6H2O + Energy*
Oxygen + Glucose Carbon Dioxide + Water + Energy
Does this equation look familiar? It should-It is the reverse of photosynthesis!
Parts of Cellular Respiration
• Cell Resp. is broken into three parts:*– 1. Glycolysis– 2. Kreb’s Cycle– 3. Electron Transport
Chain
• Each stage uses chemical energy to make ATP.
Step 1 - Glycolysis• One molecule of glucose is broken in half, producing two 3-
carbon molecules called pyruvic acid (pyruvate).– 2 ATP and 2 NADH are generated
• Occurs in ______________.Cytoplasm
Cell Respiration OverviewRespiration
StageReactants Energy
ProductsOther
ProductsNext Stop?
Glycolysis
Kreb’s Cycle
Electron Transport Chain
Cell Respiration OverviewRespiration
StageReactants Energy
ProductsOther
ProductsNext Stop?
Glycolysis Glucose
Kreb’s Cycle
Electron Transport Chain
Cell Respiration OverviewRespiration
StageReactants Energy
ProductsOther
ProductsNext Stop?
Glycolysis Glucose2 ATP
2 NADH
Kreb’s Cycle
Electron Transport Chain
Cell Respiration OverviewRespiration
StageReactants Energy
ProductsOther
ProductsNext Stop?
Glycolysis Glucose2 ATP
2 NADH2
Pyruvate
Kreb’s Cycle
Electron Transport Chain
Cell Respiration OverviewRespiration
StageReactants Energy
ProductsOther
ProductsNext Stop?
Glycolysis Glucose2 ATP
2 NADH2
Pyruvate
Pyruvate--> Kreb’s cycleNADH--> Electron Trans.
Chain ATP--> Cell use
Kreb’s Cycle
Electron Transport Chain
Cell Resp. – Why is it important?• Cells require energy
(ATP) to function
• Glucose holds energy, but it must be “released” and converted to ATP for cells to use
• Cellular respiration is the conversion of glucose to ATP
Glycolysis – Why is it important?• Glycolysis is the first
step in converting glucose to ATP
• Glucose is split up into two molecules of pyruvate– It takes 2 ATP to do this
Glycolysis • From glycolysis we get:– 2 molecules of ATP for
instant use*
– 2 molecules of NADH for ETC use
• NADH holds high energy e-*
– 2 molecules of pyruvate produce *
Advantages
Fast
Doesn’t requireoxygen
Disadvantages
Cell’s NAD+ gets used up so quickly,
glycolysis can’t go on for long
Doesn’t make all that much ATP
After Glycolysis…
Glycolysis
Fermentation
Alcoholic Fermentation
Lactic Acid Fermentation
Kreb’s CycleElectron
Transport Chain
Oxygen present
No oxygen present
Two Choices:
(Respiration)
Fermentation = No ATP
Respiration = Lots of ATP
Fermentation
• When no oxygen is present, glycolysis is followed by fermentation rather than the Kreb’s cycle
• Fermentation creates more electon carries (NAD+) so that glycolysis can make more ATP*
Fermentation
• Fermentation converts NADH to NAD+– Frees up NAD+ so
glycolysis can continue and make more ATP
• Fermentation is anaerobic*– Does not require
oxygen*
Types of Fermentation
• Alcoholic Fermentation (yeast* & bacteria)– Used to make cheese, bread, wine, buttermilk, etc..
Pyruvate + NADH alcohol + CO2 + NAD+*
Types of Fermentation• Lactic Acid Fermentation (bacterial & muscle cells,
– When muscles don’t get enough oxygen, lactic acid fermentation occurs
– Build up of lactic acid makes muscles sore
*pyruvate + NADH lactic acid + NAD+
The Rest of Cell Respiration
• If oxygen is present, the cell performs cellular respiration
• After glycolysis, 90% of the energy from glucose is still unused
• Final two steps in cell respiration extract that energy using oxygen– AEROBIC processes = require oxygen
Step 2 - The Kreb’s Cycle• Summary:
– During the Kreb’s cycle, pyruvate is broken down into CO2 + energy (NADH)*
• The Kreb’s cycle takes place in the matrix* of the mitochondria
Matrix
Kreb’s Cycle• Pyruvic acid enters the mitochondrial matrix• One carbon molecule is lost as CO2 while NAD+
NADH• Remaining two carbon molecules combine with
coenzyme A to form acetyl CoA
Kreb’s Cycle a.k.a Citric Acid Cycle
Kreb’s Cycle• Acetyl CoA is turned into CITRIC ACID.
– Kreb’s Cycle a.k.a. Citric Acid Cycle
• Citric acid is broken down and two CO2 molecules are released
• During this process, energy is released in the form of 8 NADH, 2 FADH2, and 2 ATP*
• The remaining molecule, OXALOACETIC ACID (OAA), is used to restart the cycle.
Cell Respiration OverviewRespiration
StageReactants Energy
ProductsOther
ProductsNext Stop?
Glycolysis Glucose2 ATP
2 NADH2
Pyruvate
Pyruvate--> Kreb’s cycleNADH--> Electron Trans.
Chain ATP--> Cell use
Kreb’s Cycle
Electron Transport Chain
Cell Respiration OverviewRespiration
StageReactants Energy
ProductsOther
ProductsNext Stop?
Glycolysis Glucose2 ATP
2 NADH2
Pyruvate
Pyruvate--> Kreb’s cycleNADH--> Electron Trans.
Chain ATP--> Cell use
Kreb’s Cycle 2 Pyruvate
Electron Transport Chain
Cell Respiration OverviewRespiration
StageReactants Energy
ProductsOther
ProductsNext Stop?
Glycolysis Glucose2 ATP
2 NADH2
Pyruvate
Pyruvate--> Kreb’s cycleNADH--> Electron Trans.
Chain ATP--> Cell use
Kreb’s Cycle 2 Pyruvate
2 ATP8 NADH2 FADH2
Electron Transport Chain
Cell Respiration OverviewRespiration
StageReactants Energy
ProductsOther
ProductsNext Stop?
Glycolysis Glucose2 ATP
2 NADH2
Pyruvate
Pyruvate--> Kreb’s cycleNADH--> Electron Trans.
Chain ATP--> Cell use
Kreb’s Cycle 2 Pyruvate
2 ATP8 NADH2 FADH2
6CO2 (waste)
OAA
Electron Transport Chain
Cell Respiration OverviewRespiration
StageReactants Energy
ProductsOther
ProductsNext Stop?
Kreb’s Cycle2
Pyruvate
2 ATP
8 NADH
2 FADH2
6 CO2 (waste)
OAA
CO2 --> breath
NADH & FADH2--> ETC
OAA --> restart Kreb’s
ATP--> cell use
Electron Transport Chain
Krebs Results
• From all this we got 3 different forms of energy:
1. ATP – immediate cell usage
2. NADH
3. FADH2
Electron carriers that will bring high-energy
electrons to ETC
Step 3 – Electron Transport Chain
What did the ETC do in photo-
synthesis?
Step 3 – Electron Transport Chain (ETC)• The electron transport chain uses high-energy
electrons from the Kreb’s cycle to make ATP• Occurs in ____________________.*Cristae (inner membrane)
Cristae (inner membrane)
Electron Transport Chain• Electrons from NADH and FADH2 are
transported to the ETC*
• At the end of the ETC sits oxygen*, which is very electronegative (it draws electrons near it) - this causes the electrons to travel down the ETC towards oxygen– Oxygen is the terminal electron acceptor
• At the end of the chain, a protein combines the electrons with H+ and O- to make H2O*
Electron Transport Chain• Every time 2 electrons move down the ETC, their
energy pumps H+ ions into the inner membrane space, creating a concentration gradient*
• The H+ ions then want to diffuse from the inner membrane space back to the matrix*
Meanwhile…
Electron Transport Chain• To cross the
membrane, H+ moves through ATP synthase molecules making a gradient with the H+ *– Each time they do, it
creates ATP – Chemiosmosis*
• Each pair of electrons yields 3 ATP molecules
Cell Respiration OverviewRespiration
StageReactants Energy
ProductsOther
ProductsNext Stop?
Glycolysis Glucose2 ATP
2 NADH2
Pyruvate
Pyruvate--> Kreb’s cycleNADH--> Electron Trans.
Chain ATP--> Cell use
Kreb’s Cycle 2 Pyruvate
2 ATP8 NADH2FADH2
6 CO2 (waste)
OAA
CO2 --> breath
NADH & FADH2--> Electron Trans. ChainOAA --> restart Kreb’s
ATP--> cell use
Electron Transport Chain
Cell Respiration OverviewRespiration
StageReactants Energy
ProductsOther
ProductsNext Stop?
Glycolysis Glucose2 ATP
2 NADH2
Pyruvate
Pyruvate--> Kreb’s cycleNADH--> Electron Trans.
Chain ATP--> Cell use
Kreb’s Cycle 2 Pyruvate
2 ATP8 NADH2 FADH2
6 CO2 (waste)
OAA
CO2 --> breath
NADH & FADH2--> Electron Trans. ChainOAA --> restart Kreb’s
ATP--> cell use
Electron Transport Chain
NADHFADH2
Cell Respiration OverviewRespiration
StageReactants Energy
ProductsOther
ProductsNext Stop?
Glycolysis Glucose2 ATP
2 NADH2
Pyruvate
Pyruvate--> Kreb’s cycleNADH--> Electron Trans.
Chain ATP--> Cell use
Kreb’s Cycle 2 Pyruvate
2 ATP8 NADH2 FADH2
6 CO2 (waste)
OAA
CO2 --> breath
NADH & FADH2--> Electron Trans. ChainOAA --> restart Kreb’s
ATP--> cell use
Electron Transport Chain
NADHFADH2
32 ATP
Cell Respiration OverviewRespiration
StageReactants Energy
ProductsOther
ProductsNext Stop?
Glycolysis Glucose2 ATP
2 NADH2
Pyruvate
Pyruvate--> Kreb’s cycleNADH--> Electron Trans.
Chain ATP--> Cell use
Kreb’s Cycle 2 Pyruvate
2 ATP8 NADH2 FADH2
6 CO2 (waste)
OAA
CO2 --> breath
NADH & FADH2--> Electron Trans. ChainOAA --> restart Kreb’s
ATP--> cell use
Electron Transport Chain
NADHFADH2
32 ATP H20
Cell Respiration OverviewRespiration
StageReactants Energy
ProductsOther
ProductsNext Stop?
Glycolysis Glucose2 ATP
2 NADH2
Pyruvate
Pyruvate--> Kreb’s cycleNADH--> Electron Trans.
Chain ATP--> Cell use
Kreb’s Cycle 2 Pyruvate
2 ATP8 NADH2 FADH2
6 CO2 (waste)
OAA
CO2 --> breath
NADH & FADH2--> Electron Trans. ChainOAA --> restart Kreb’s
ATP--> cell use
Electron Transport Chain
NADHFADH2
32 ATP H20
ATP--> Cell useH20-->
NAD+ & FAD+ --> recycled
The Totals
Glycolysis ? ATP
Kreb’s Cycle &Electron Transport ?? ATP
_______
Total ?? ATP
The Totals
Glycolysis 2 ATP
Kreb’s Cycle &Electron Transport ?? ATP
_______
Total ?? ATP
The Totals
Glycolysis 2 ATP
Kreb’s Cycle &Electron Transport 34 ATP
_______
Total ?? ATP
The Totals
Glycolysis 2 ATP
Kreb’s Cycle &Electron Transport 34 ATP
_______
Total 36 ATP
Think about it…
• What types of cells can perform cellular respiration:– Animal cells?– Plant cells?– Bacterial cells?– Yeast cells?– Anything else you can think of?
Think about this one…
• In what situations would a cell perform fermentation over respiration? Explain.
Think About This One!
• Why might you lose weight (a lot of weight) if your mitochondria suddenly lost the ability to couple electron transport to the production of ATP?
Comparison of Fermentation to Cellular Respiration
Lactic Acid Alcoholic Cellular respirationglucose
glycolysis (pyruvic acid)
lactic acid
2 ATP
glucose glucose
glycolysis (pyruvic acid) glycolysis (pyruvic acid)
carbon dioxide
alcohol
2 ATP 36 ATP
water
carbon dioxide
Cellular Respiration vs. Fermentation
How Do Other Food Molecules Enter Metabolism?• Fat, carbohydrates and proteins enter the
cellular respiration pathway at different points
• The most likely point is at acetyl CoA
• Overall Cell Respiration