Download Week III Lecture I slides

9/7/2015
THE CELLULAR RESPIRATION SAGA:
Glycolysis, Fermentation & Pyruvate Oxidation
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HOW DO WE GET ATP?
ATP is a product of cellular respiration
O2
Breathing
CO2
• Breath in O2
• O2 diffuses into bloodstream
• O2 diffuses into cells through the plasma membrane
Lungs
O2
Transported in
bloodstream
CO2
Muscle cells carrying out
Cellular Respiration
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CELLULAR RESPIRATION Oxygen molecules diffuse across the plasma membrane into the cell, then into the mitochondria
CO2
O2
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CELLULAR RESPIRATION
MANY steps result in products necessary to live
C6H12O6
6 O2
6 CO2
*Glucose
Oxygen
Carbon
dioxide
6 H2O
ATP
Heat
Water
*Glucose is the preferred molecule for respiration, but we can use 4
other types also
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CELLULAR RESPIRATION
Only about 34% of energy from glucose is transferred to ATP
C6H12O6
6 O2
6 CO2
6 H2O
Glucose
Oxygen
Carbon
dioxide
ATP
Heat
Water
Potential energy
Reactants
Amount of
energy released
Energy
Products
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PLAYERS OF CELLULAR RESPIRATION
Processes of oxidation and reduction (redox reactions)
• OXIDATION is the loss of electrons from a substance
• REDUCTION is the addition of electrons to a substance
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PLAYERS OF CELLULAR RESPIRATION
NAD+ is a coenzyme that accepts electrons and shuttles them around
• Coenzyme
• Organic molecule made from niacin (vitamin B3)
Some molecule with yummy electrons
• Take your vitamins!
NAD+
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PLAYERS OF CELLULAR RESPIRATION
NADH can hold two electrons
Becomes oxidized
NAD+
+ 2H
Becomes reduced
2 H+ + 2
+2H
NADH
H+
(carries)
2 electrons)
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PLAYERS OF CELLULAR RESPIRATION
Electron transport chains
NAD+
NADH
2
Energy released
and available
for making
ATP
2
1
−
2
O2
H2O
2 H+
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GLYCOLYSIS
Operation: “Break Down Glucose!”
Happens in the cytosol / cytoplasm
• Happens in 9 steps • No OXYGEN REQUIRED
• Phase 1: Energy Investment Phase (steps 1‐4)
• Phase 2: Energy Payoff Phase (steps 5‐9)
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GLYCOLYSIS
Reactants at each step are products for the next step.
Each step has its own enzyme(s)
Enzyme
Enzyme
A
Reaction
B
Enzyme
C
Reaction
D
Reaction
Glucose
2 Pyruvate
Glucose
GLYCOLYSIS
Energy Investment Phase
(Steps 1‐4)
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Glucose
ATP
Step
1
ADP
P
Less stable 6 carbon sugar
P
Even less stable 6 carbon sugar
P
EVEN less stable 6 carbon sugar
2
Invest 2 ATP molecules to break glucose into smaller sugars
ATP
3
ADP
P
4
P
P
Glyceraldehyde 3-phosphate
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(G3P)
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GLYCOLYSIS
Energy Payoff Phase Step 5 is a redox reaction
Two 3 Carbon Sugars
P
P
Redox
reaction
NAD+
NAD+
5
P
NADH
+ H+
Inorganic
Phosphate
5
P
NADH
+ H+
P
P
P
P
Two 3 Carbon Sugars
Becomes oxidized
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+2H
+2H
NAD+
+ 2H
Becomes reduced
2 H+ + 2
H+
NADH
(carries)
14
2 electrons)
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GLYCOLYSIS
Energy Payoff Phase (steps 6‐9)
P
P
ADP
P
P
ADP
6
6
ATP
ATP
P
4 ‐ ATP molecules are produced by SUBSTRATE LEVEL PHOSPHORYLATION
P
7
7
P
P
8
H2O
8
H2O
P
P
ADP
ADP
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9
ATP
ATP
Pyruvate
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SUBSTRATE LEVEL PHOSPHORYLATION
Transferring a phosphate group directly to an ADP
Enzyme
P
Enzyme
ADP
ATP
P
Substrate
(3 Carbon Sugar)
P
Product
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GLYCOLYSIS
Energy Payoff Phase (steps 6‐9)
P
P
P
ADP
P
ADP
6
6
ATP
ATP
P
P
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7
P
P
8
H2O
8
H2O
P
P
ADP
ADP
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9
ATP
ATP
Pyruvate
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GLYCOLYSIS
Starting with glucose
• 4 ATP’s made (synthesized)
• ‐2 ATP’s invested
= 2 net ATP’s synthesized
•
ATP
ATP
2 Pyruvate molecules synthesized from 1 glucose
• No Oxygen required!
• 2 NAD+s reduced to NADH’s
= 4 electrons banked
NADH
NADH
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GLYCOLYSIS
An ancient process that occurs in almost any living organism
Glycolysis can lead to aerobic or anaerobic respiration
You are here!
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LIFE AFTER GLYCOLYSIS
Glucose
2 ADP
+2 P
• Anaerobic
• Converting pyruvate to alcohol and CO2 2
ATP
Glycolysis
Option1: Alcohol Fermentation (EX: Yeast)
2 NAD+
2 NADH
• Recycles NADH to NAD+ (redox)
2 Pyruvate
2 NADH
2 CO2
2 NAD+
2 Ethanol
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LIFE AFTER GLYCOLYSIS
Option 2: Lactic Acid Fermentation (EX: Dairy)
2 ADP
+2 P
• Anaerobic
2
ATP
Glycolysis
Glucose
• Converting pyruvate to lactic acid and CO2 2 NAD+
2 NADH
• Recycles NADH to NAD+ (redox)
2 Pyruvate
2 NADH
2 NAD+
2 Lactate
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LIFE AFTER GLYCOLYSIS
Option 3: Continue with aerobic respiration
You are here!
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AEROBIC RESPIRATION
Next step: Pyruvate Oxidation in the mitochondria
Mitochondrion
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PYRUVATE OXIDATION
Cleans up the two pyruvates for the citric acid cycle
NAD+
NADH + H+
2
CoA
Pyruvate
Acetyl coenzyme A
1
CO2
3
Coenzyme A
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COMPARE OPTIONS
Fermentation vs. Pyruvate Oxidation
Fermentation
Pyruvate Oxidation
•
•
•
•
•
•
•
•
Follows Glycolysis
Anaerobic
Recycle NADH
Make lactic acid or Alcohol
• Make CO2
Follow Glycolysis
Aerobic
No recycling needed
Make acetyl CoA
(coenzyme)
• Make CO2
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Electrons carried by NADH
Glycolysis
Glucose
Pyruvate
CYTOSOL
ATP
Pyruvate
Oxidation
Citric Acid
Cycle
FADH2
Oxidative
Phosphorylation
(Electron transport
and chemiosmosis)
MITOCHONDRION
Substrate-level
phosphorylation
ATP
Substrate-level
phosphorylation
ATP
Oxidative
phosphorylation
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