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CHAPTER 9
CELLULAR RESPIRATION: HARVESTING CHEMICAL ENERGY
PowerPoint® Lecture Presentations for
Biology
Eighth Edition
Neil Campbell and Jane Reece
1
Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
OVERVIEW: LIFE IS WORK
• LIVING CELLS REQUIRE ENERGY
FROM OUTSIDE SOURCES
• SOME ANIMALS, SUCH AS THE
GIANT PANDA, OBTAIN ENERGY
BY EATING PLANTS, AND SOME
ANIMALS FEED ON OTHER
ORGANISMS THAT EAT PLANTS
• THOSE THAT CAN MAKE THEIR
OWN FOOD: AUTOTROPHS
• THOSE THAT RECEIVE NUTRIENTS
AND ENERGY FROM OTHER
ORGANISMS: HETEROTROPHS
2
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• ENERGY FLOWS INTO AN
ECOSYSTEM AS SUNLIGHT
AND LEAVES AS HEAT
• PHOTOSYNTHESIS GENERATES
O2 AND ORGANIC
MOLECULES, WHICH ARE USED
IN CELLULAR RESPIRATION
• CELLS USE CHEMICAL ENERGY
STORED IN ORGANIC
MOLECULES TO REGENERATE
ATP, WHICH POWERS WORK 3
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CONCEPT 9.1: CATABOLIC PATHWAYS YIELD
ENERGY BY OXIDIZING ORGANIC FUELS
4
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CATABOLIC PATHWAYS AND PRODUCTION
OF ATP
(THINK OF CATASTROPHES BREAKING
THINGS DOWN)
• FERMENTATION IS A PARTIAL DEGRADATION OF SUGARS THAT
OCCURS WITHOUT O2 (YEAST, BACTERIA)
• AEROBIC RESPIRATION CONSUMES ORGANIC MOLECULES AND O2
AND YIELDS ATP (VERY EFFICIENT AND IS THE PREFERRED FORM OF
RESPIRATION)
• ANAEROBIC RESPIRATION IS SIMILAR TO AEROBIC RESPIRATION BUT
CONSUMES COMPOUNDS OTHER THAN O2 (LEAST PREFERRED
METHOD BECAUSE NOT AS EFFICIENT, WILL ONLY OCCUR IF NO
OTHER CHOICE)
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5
CELLULAR RESPIRATION INCLUDES BOTH AEROBIC AND ANAEROBIC
RESPIRATION BUT IS OFTEN USED TO REFER TO AEROBIC RESPIRATION
ALTHOUGH CARBOHYDRATES, FATS, AND PROTEINS ARE ALL CONSUMED
AS FUEL, IT IS HELPFUL TO TRACE CELLULAR RESPIRATION WITH THE SUGAR
GLUCOSE:
C6H12O6 + 6 O2  6 CO2 + 6 H2O + ENERGY (ATP + HEAT)
(GLUCOSE)
(OXYGEN) > (CARBON DIOXIDE)
(WATER)
YES, YOU NEED TO KNOW THIS FORMULA!
6
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THE BREAKDOWN OF GLUCOSE
• IS EXERGONIC (GIVES OFF ENERGY)
• ∆ G = -686 KCAL/MOL
• CAN HAPPEN SPONTANEOUSLY
7
THE PRINCIPLE OF REDOX
• CHEMICAL REACTIONS THAT
TRANSFER ELECTRONS BETWEEN
REACTANTS ARE CALLED
OXIDATION-REDUCTION
REACTIONS, OR REDOX
REACTIONS
• IN OXIDATION, A SUBSTANCE
LOSES ELECTRONS, OR IS OXIDIZED
• IN REDUCTION, A SUBSTANCE
GAINS ELECTRONS, OR IS REDUCED
(THE AMOUNT OF POSITIVE
CHARGE IS REDUCED)
9
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THE ELECTRON DONOR IS
CALLED THE REDUCING
AGENT (THIS IS THE OIL PART)
THE ELECTRON RECEPTOR IS
CALLED THE OXIDIZING
AGENT (THIS IS THE RIG PART)
SOME REDOX REACTIONS DO
NOT TRANSFER ELECTRONS
BUT CHANGE THE ELECTRON
SHARING IN COVALENT
BONDS
AN EXAMPLE IS THE
REACTION BETWEEN
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12
Fig. 9-UN3
OXIDATION OF ORGANIC FUEL MOLECULES
DURING CELLULAR RESPIRATION
During cellular respiration, the fuel (such as glucose) is oxidized,
and O2 is reduced:
becomes oxidized
becomes reduced
The electrons lose potential energy along the way and energy is
released, allowing it to be used for ATP synthesis
15
BIG PICTURE FOR ELECTRONS
• GLUCOSE -> NADH + FADH2 -> ELECTRON TRANSPORT TRAIN ->
OXYGEN
23
THE STAGES OF CELLULAR RESPIRATION: A
PREVIEW
HOW OXYGEN IS KILLING YOU
• CELLULAR RESPIRATION HAS THREE STAGES:
• GLYCOLYSIS (BREAKS DOWN GLUCOSE (6 CARBONS) INTO TWO
MOLECULES OF PYRUVATE (3 CARBONS APIECE)
• THE CITRIC ACID CYCLE (COMPLETES THE BREAKDOWN OF
GLUCOSE)
• OXIDATIVE PHOSPHORYLATION (ACCOUNTS FOR MOST OF THE ATP SYNTHESIS)
OXIDATIVE PHOSPHORYLATION ACCOUNTS FOR ALMOST 90% OF THE ATP
GENERATED BY CELLULAR RESPIRATION
• A SMALLER AMOUNT OF ATP IS FORMED IN GLYCOLYSIS AND THE CITRIC ACID
CYCLE BY SUBSTRATE-LEVEL PHOSPHORYLATION
24
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Fig. 9-6-1
Electrons
carried
via NADH
Glycolysis
Pyruvate
Glucose
Cytosol
ATP
Substrate-level
phosphorylation
25
Fig. 9-6-2
Electrons carried
via NADH and
FADH2
Electrons
carried
via NADH
Citric
acid
cycle
Glycolysis
Pyruvate
Glucose
Mitochondrion
Cytosol
ATP
ATP
Substrate-level
phosphorylation
Substrate-level
phosphorylation
26
Fig. 9-6-3
Electrons carried
via NADH and
FADH2
Electrons
carried
via NADH
Citric
acid
cycle
Glycolysis
Pyruvate
Glucose
Oxidative
phosphorylation:
electron transport
and
chemiosmosis
Mitochondrion
Cytosol
ATP
ATP
ATP
Substrate-level
phosphorylation
Substrate-level
phosphorylation
Oxidative
phosphorylation
27
Fig. 9-7
Substrate level phosphorylation
Enzyme
Enzyme
ADP
P
Substrate
+
ATP
Product
28
CONCEPT 9.2: GLYCOLYSIS HARVESTS CHEMICAL
ENERGY BY OXIDIZING GLUCOSE TO PYRUVATE
• GLYCOLYSIS (“SPLITTING OF SUGAR”) BREAKS DOWN GLUCOSE, A 6
CARBON SUGAR INTO TWO MOLECULES OF PYRUVATE EACH WITH 3
CARBONS, THIS IS AN ANAEROEBIC STEP IN CELL RESPIRATION
• GLYCOLYSIS OCCURS IN THE CYTOPLASM AND HAS TWO MAJOR PHASES:
• ENERGY INVESTMENT PHASE
• ENERGY PAYOFF PHASE
29
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WARNING:
• PER COLLEGE BOARD: MEMORIZATION OF THE STEPS IN GLYCOLYSIS
AND THE KREBS (CITRIC ACID) CYCLE, OR OF THE STRUCTURES OF THE
MOLECULES AND THE NAMES OF THE ENZYMES INVOLVED, ARE
BEYOND THE SCOPE OF THE COURSE AND THE AP EXAM
• EXCEPT FOR ATP SYNTHASE
30
CONCENTRATE ON BIG PICTURE STUFF
• WHAT SUBSTRATE AND ENERGY GOES IN
• WHAT SUBSTRATE/PRODUCT AND ENERGY COMES OUT
31
GLYCOLYSIS (BREAKDOWN)- HAPPENS IN THE
CYTOSOL
Substrate level
phosphorylation
32
• HTTP://WWW.YOUTUBE.COM/WATCH?V=CLXCQ0WFJKK&FEATURE=
RELATED
• CELLULAR RESPIRATION SONG TO “HEY THERE DELILAH”
33
Fig. 9-8
Energy investment phase
Glucose
2 ADP + 2 P
2 ATP
used
4 ATP
formed
Energy payoff phase
4 ADP + 4 P
2 NAD+ + 4 e– + 4 H+
2 NADH + 2 H+
2 Pyruvate + 2 H2O
Net
Glucose
4 ATP formed – 2 ATP used
2 Pyruvate + 2 H2O
2 ATP
34
2
NAD+
+ 4
e–
+4
H+
2 NADH + 2
H+
BIG PICTURE:
• WHAT GOES IN TO GLYCOLYSIS?
• WHAT COMES OUT OF GLYCOLYSIS?
• WHERE DOES GLYCOLYSIS OCCUR?
• IS IT ANAEROBIC OR AEROBIC?
• WHAT ENERGY GOES IN?
• WHAT ENERGY COMES OUT?
• WHAT IS THE NET ENERGY GAIN?
35
ANSWER:
• GLUCOSE (6 CARBONS) GO IN
• 2 PYRUVATES COME OUT (3 CARBONS EACH)
• HAPPENS IN THE CYTOSOL OF THE CELL (NOT THE MITOCHONDRIA)
• IT IS ANAEROBIC
• INPUT OF 2 ATP
• OUTPUT OF 2 NADH AND 4 ATP
• OVERALL 2 NADH AND 2 ATP GAINED
36
CONCEPT 9.3: THE CITRIC ACID CYCLE
COMPLETES THE ENERGY-YIELDING OXIDATION
OF ORGANIC MOLECULES
REMEMBER: GLYCOLYSIS IS AN ANAEROBIC PROCESS THAT YIELDS 2
PYRUVATE
LESS THAN 25% OF THE CHEMICAL ENERGY IN GLUCOSE IS RELEASED FROM
GLYCOLYSIS
37
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IN THE PRESENCE OF O2 (MORE EFFICIENT), PYRUVATE ENTERS THE
MITOCHONDRION THROUGH ACTIVE TRANSPORT
BEFORE THE CITRIC ACID CYCLE CAN BEGIN, PYRUVATE MUST BE CONVERTED TO
ACETYL COA, (WHICH IS ACETYL COENZYME) A BY THE CAPTURE OF ELECTRONS
WHICH LINKS THE CYCLE TO GLYCOLYSIS
38
THE KREBS CYCLE
IS ALSO CALLED:
TRICARBOXYLIC ACID CYCLE (TCA)
OR
THE CITRIC ACID CYCLE
39
The net yield from the
Krebs cycle per
glucose:
 six CO2 molecules,
two ATP,
 eight NADH,
 and two FADH2.
 INCREDIBLY
IMPORTANT:
 There are 2 pyruvates
that need to go through
this cycle, so this wheel
turns 2x per glucose
40
WHERE ARE WE SO FAR WITH ENERGY:
• HOW MANY ATP DID WE NET FROM GLYCOLYSIS?
• HOW MANY ATP DID WE NET FROM KREBS?
• HOW MANY NADH DID WE NET FROM GLYCOLYSIS
• HOW MANY NADH DID WE NET FROM KREBS?
• HOW MANY FADH2 DID WE NET FROM KREBS?
41
ANSWER:
• 10 NADH
• 4 ATP
• 2 FADH2
42
• THE CITRIC ACID CYCLE,
ALSO CALLED THE KREBS
CYCLE, TAKES PLACE
WITHIN THE
MITOCHONDRIAL MATRIX
• THE CYCLE OXIDIZES
ORGANIC FUEL DERIVED
FROM PYRUVATE,
GENERATING 1 ATP, 3
NADH, AND 1 FADH2 PER
TURN
• THERE ARE 2 TURNS PER
GLUCOSE
43
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Fig. 9-11
Pyruvate
CO2
NAD+
CoA
NADH
+ H+
Acetyl CoA
CoA
CoA
Citric
acid
cycle
FADH2
2 CO2
3 NAD+
3 NADH
FAD
+ 3 H+
ADP + P i
ATP
44
• THE CITRIC ACID CYCLE HAS EIGHT STEPS, EACH CATALYZED BY A SPECIFIC
ENZYME
• THE ACETYL GROUP OF ACETYL COA JOINS THE CYCLE BY COMBINING WITH
OXALOACETATE, FORMING CITRATE
• THE NEXT SEVEN STEPS DECOMPOSE THE CITRATE BACK TO OXALOACETATE,
MAKING THE PROCESS A CYCLE
• THE NADH AND FADH2 PRODUCED BY THE CYCLE RELAY ELECTRONS
EXTRACTED FROM FOOD TO THE ELECTRON TRANSPORT CHAIN
45
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Fig. 9-12-1
This molecule
has 2 Carbon
Acetyl CoA
CoA—SH
This molecule
Has 4 carbons
1
They combine
To make a 6 C
molecule
Oxaloacetate
Citrate
Citric
acid
cycle
46
Fig. 9-12-2
Acetyl CoA
CoA—SH
H2O
1
Oxaloacetate
2
Citrate
Isocitrate
Citric
acid
cycle
Still 6 carbons, just
rearranged
47
Fig. 9-12-3
Acetyl CoA
CoA—SH
1
H2O
Oxaloacetate
2
Citrate
Isocitrate
NAD+
Citric
acid
cycle
NADH
+ H+
3
CO2
-Ketoglutarate
Lost a C as
byproduct
48
Fig. 9-12-4
Acetyl CoA
CoA—SH
1
H2O
Oxaloacetate
2
Citrate
Isocitrate
NAD+
Citric
acid
cycle
NADH
+ H+
3
CO2
CoA—SH
-Ketoglutarate
4
NAD+
Succinyl
CoA
CO2
NADH
+ H+
49
Lost another C
Fig. 9-12-5
Acetyl CoA
CoA—SH
1
H2O
Oxaloacetate
2
Citrate
Isocitrate
NAD+
Citric
acid
cycle
NADH
+ H+
3
CO2
CoA—SH
-Ketoglutarate
4
CoA—SH
Still 4 C but
rearranged
5
NAD+
Succinate
GTP GDP
Pi
Succinyl
CoA
CO2
NADH
+ H+
ADP
50
ATP
Fig. 9-12-6
Acetyl CoA
CoA—SH
H2O
1
Oxaloacetate
2
Citrate
Isocitrate
NAD+
Still 4 C but
rearranged
Citric
acid
cycle
NADH
+ H+
3
CO2
Fumarate
CoA—SH
6
-Ketoglutarate
4
CoA—SH
5
FADH2
NAD+
FAD
Succinate
GTP GDP
Pi
Succinyl
CoA
CO2
NADH
+ H+
ADP
51
ATP
Fig. 9-12-7
Acetyl CoA
CoA—SH
Still 4 C but
rearranged
H2O
1
Oxaloacetate
2
Malate
Citrate
Isocitrate
NAD+
Citric
acid
cycle
7
H2O
NADH
+ H+
3
CO2
Fumarate
CoA—SH
-Ketoglutarate
4
6
CoA—SH
5
FADH2
NAD+
FAD
Succinate
GTP GDP
Pi
Succinyl
CoA
CO2
NADH
+ H+
ADP
52
ATP
Fig. 9-12-8
Acetyl CoA
CoA—SH
NADH
+H+
H2O
1
NAD+
8
Oxaloacetate
2
Malate
Citrate
Isocitrate
NAD+
Citric
acid
cycle
7
H2O
NADH
+ H+
3
CO2
Fumarate
CoA—SH
6
-Ketoglutarate
4
CoA—SH
5
FADH2
NAD+
FAD
Succinate
GTP GDP
Pi
Succinyl
CoA
CO2
NADH
+ H+
ADP
53
ATP
CONCEPT 9.4: DURING OXIDATIVE
PHOSPHORYLATION, CHEMIOSMOSIS COUPLES
ELECTRON TRANSPORT TO ATP SYNTHESIS
• FOLLOWING GLYCOLYSIS AND THE CITRIC ACID CYCLE, NADH AND FADH2
ACCOUNT FOR MOST OF THE ENERGY EXTRACTED FROM FOOD
• REMEMBER THEY ACCEPTED ELECTRONS AND AT LEAST ONE PROTON
• THESE TWO ELECTRON CARRIERS DONATE ELECTRONS TO THE ELECTRON
TRANSPORT CHAIN, WHICH POWERS ATP SYNTHESIS VIA OXIDATIVE
PHOSPHORYLATION
• VIRTUAL CELL- ELECTRON TRANSPORT CHAIN
54
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THE PATHWAY OF ELECTRON TRANSPORT
• THE ELECTRON TRANSPORT CHAIN IS IN THE CRISTAE OF THE
MITOCHONDRION
• MOST OF THE CHAIN’S COMPONENTS ARE PROTEINS, WHICH EXIST IN
MULTIPROTEIN COMPLEXES NUMBERED I THROUGH IV
• THE CARRIERS ALTERNATE REDUCED AND OXIDIZED STATES AS THEY ACCEPT
AND DONATE ELECTRONS
• WHAT HAPPENS, A CARRIER ACCEPTS AN ELECTRON THEN HANDS IT DOWN
TO THE NEXT CARRIER
• ELECTRONS DROP IN FREE ENERGY AS THEY GO DOWN THE CHAIN AND ARE
FINALLY PASSED TO O2, FORMING H2O
55
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Fig. 9-13
NADH
You do not need to
Know the electron
Carrier proteins (called
Cytochromes)
50
2 e–
NAD+
FADH2
2 e–
40

FMN
FAD
Multiprotein
complexes
FAD
Fe•S 
Fe•S
Q
You need to know that
NADH
And
FADH2
Give their electrons that
They just got from
KREBS to the ETC
No ATP is made
Directly, it breaks the
Fall from high free
To smaller more
Manageable steps
ATP is made through
chemiosmosis

Cyt b
30
Fe•S
Cyt c1
I
V
Cyt c
Cyt a
Cyt a3
20
10
2 e–
(from NADH
or FADH2)
0
2 H+ + 1/2 O2
56
H2O
• ELECTRONS ARE TRANSFERRED FROM
NADH OR FADH2 TO THE ELECTRON
TRANSPORT CHAIN
• ELECTRONS ARE PASSED THROUGH A
NUMBER OF PROTEINS INCLUDING
CYTOCHROMES (EACH WITH AN IRON
ATOM) TO O2
• PROTONS ARE RELEASED INTO THE
INNER MEMBRANE SPACE OF THE
MITOCHONDRIA
• THE ELECTRON TRANSPORT CHAIN
GENERATES NO ATP
• THE CHAIN’S FUNCTION IS TO BREAK
THE LARGE FREE-ENERGY DROP FROM
FOOD TO O2 INTO SMALLER STEPS THAT
RELEASE ENERGY IN MANAGEABLE
AMOUNTS
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57
CHEMIOSMOSIS: THE ENERGY-COUPLING
MECHANISM
• ETC OCCURS IN THE INNER MEMBRANE OF THE
MITOCHONDRIA
• ELECTRON TRANSFER IN THE ELECTRON TRANSPORT
CHAIN CAUSES PROTEINS TO PUMP H+ FROM THE
MITOCHONDRIAL MATRIX TO THE INTERMEMBRANE
SPACE CAUSING A PROTON GRADIENT THAT HAS
POTENTIAL TO DO WORK
58
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• H+ THEN MOVES BACK ACROSS THE
MEMBRANE, PASSING THROUGH
CHANNELS IN ATP SYNTHASE (AN
ENZYME)
• ATP SYNTHASE USES THE
EXERGONIC FLOW OF H+ TO DRIVE
PHOSPHORYLATION OF ATP FROM
ADP
• THIS IS AN EXAMPLE OF
CHEMIOSMOSIS, THE USE OF
ENERGY IN A H+ GRADIENT TO
DRIVE CELLULAR WORK
59
Fig. 9-14
INTERMEMBRANE SPACE
H+
Stator
Rotor
Internal
rod
Catalytic
knob
ADP
+
P
i
ATP
MITOCHONDRIAL MATRIX
60
• THE ENERGY STORED IN A H+ GRADIENT ACROSS A MEMBRANE COUPLES THE
REDOX REACTIONS OF THE ELECTRON TRANSPORT CHAIN TO ATP SYNTHESIS
• THE H+ GRADIENT IS REFERRED TO AS A PROTON-MOTIVE FORCE,
EMPHASIZING ITS CAPACITY TO DO WORK
• ATP SYNTHASE BIOLOGICAL GRADIENTS VIDEO
61
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Fig. 9-16
Inner membrane space
H+
H+
H+
H+
Protein complex
of electron
carriers
Cyt c
V
Q


ATP
synthase

FADH2
NADH
2 H+ + 1/2O2
H2O
FAD
NAD+
ADP + P i
(carrying electrons
from food)
ATP
H+
1 Electron transport chain
2 Chemiosmosis
matrix
Oxidative phosphorylation
62
AN ACCOUNTING OF ATP PRODUCTION BY CELLULAR
RESPIRATION
• DURING CELLULAR RESPIRATION, MOST ENERGY FLOWS IN THIS SEQUENCE:
GLUCOSE  NADH AND FADH2  ELECTRON TRANSPORT CHAIN 
PROTON-MOTIVE FORCE  ATP
• ABOUT 40% OF THE ENERGY IN A GLUCOSE MOLECULE IS TRANSFERRED TO
ATP DURING CELLULAR RESPIRATION, MAKING ABOUT 38 ATP
63
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Fig. 9-17
Electron shuttles
span membrane
CYTOSOL
2 NADH
Glycolysis
Glucose
2
Pyruvate
MITOCHONDRION
2 NADH
or
2 FADH2
6 NADH
2 NADH
2
Acetyl
CoA
+ 2 ATP
Citric
acid
cycle
+ 2 ATP
Maximum per glucose:
2 FADH2
Oxidative
phosphorylation:
electron transport
and
chemiosmosis
+ about 32 or 34 ATP
About
36 or 38 ATP
64
CONCEPT 9.5: FERMENTATION AND
ANAEROBIC RESPIRATION ENABLE CELLS TO
PRODUCE ATP WITHOUT THE USE OF
OXYGEN
• MOST CELLULAR RESPIRATION REQUIRES O2 TO PRODUCE ATP
• GLYCOLYSIS CAN PRODUCE ATP WITH OR WITHOUT O2 (IN AEROBIC OR
ANAEROBIC CONDITIONS)
• IN THE ABSENCE OF O2, GLYCOLYSIS COUPLES WITH FERMENTATION OR
ANAEROBIC RESPIRATION TO PRODUCE ATP
65
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• ANAEROBIC RESPIRATION USES
AN ELECTRON TRANSPORT
CHAIN WITH AN ELECTRON
ACCEPTOR OTHER THAN O2, FOR
EXAMPLE SULFATE
• FERMENTATION USES
PHOSPHORYLATION INSTEAD OF
AN ELECTRON TRANSPORT
CHAIN TO GENERATE ATP
66
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TYPES OF FERMENTATION
• FERMENTATION CONSISTS OF GLYCOLYSIS PLUS REACTIONS THAT REGENERATE NAD+, WHICH CAN BE REUSED
BY GLYCOLYSIS
• PYRUVIC ACID CAN GO THROUGH 3 DIFFERENT PATHWAYS
KREB’S IF OXYGEN IS PRESENT
LACTIC ACID FERMENTATION
ALCOHOL FERMENTATION
67
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AFTER GLYCOLYSIS IN ANAEROBES
THERE ARE TWO KINDS OF FERMENTATION
FERMENTATION IS BREAKING DOWN SUGAR WITHOUT OXYGEN
IN ONE TYPE SUGAR BREAKS DOWN INTO LACTIC ACID
C6H12O6  2 H+ + 2 C3H5O3-
68
LACTIC ACID FERMENTATION
THIS IS DONE BY YOUR MUSCLES WHEN THE DEMAND FOR ATP IS
HIGH, BUT YOU ARE LOW IN OXYGEN. (WHILE WORKING OUT) THIS
CAN CAUSE SORENESS IN THE MUSCLES.
KREBS AND THE ETC SLOW DOWN, DECREASING THE ATP
PRODUCTION
MUSCLE CELLS CAN STILL DO A BIT OF GLYCOLYSIS W/O OXYGEN
GLUCOSE IS CONVERTED TO PYRUVIC ACID THEN AN ENZYME
CONVERTS THAT TO LACTIC ACID
THIS REACTION FREES UP THE NAD WHILE GIVING 2 ATP (ANOTHER
NADH IS REOXIDIZED DURING FERMENTATION)
THE LACTIC ACID BUILDS UP, CAUSING FATIGUE, AND THE MUSCLE
69
• IN LACTIC ACID FERMENTATION, PYRUVATE IS REDUCED TO NADH,
FORMING LACTATE AS AN END PRODUCT, WITH NO RELEASE OF CO2
• LACTIC ACID FERMENTATION BY SOME FUNGI AND BACTERIA IS USED TO
MAKE CHEESE AND YOGURT
• HUMAN MUSCLE CELLS USE LACTIC ACID FERMENTATION TO GENERATE ATP
WHEN O2 IS SCARCE
70
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Fig. 9-18b
2 ADP + 2 P i
Glucose
2 ATP
Glycolysis
2 NAD+
2 NADH
+ 2 H+
2 Pyruvate
2 Lactate
71
(b) Lactic acid fermentation
ALCOHOL FERMENTATION
• GLYCOLYSIS IS ANAEROBIC AND YIELDS 2 ATP, AND 2 NADH AND
PYRUVATE (REALLY PYRUVIC ACID THAT GETS THE ACETYL COENZYME A
ATTACHED)
• YEASTS/BACTERIA CONVERT PYRUVIC ACID TO ETHYL ALCOHOL
• DURING ALCOHOL FERMENTATION NADH LOSES ELECTRONS AND THE H+
• THE NAD IS FREED TO GO BACK THROUGH GLYCOLYSIS
• THE OVERALL ENERGY FOR THE YEAST/BACTERIA WOULD ONLY BE THE 2
ORIGINAL ATP
• JUST ENOUGH TO STAY ALIVE
72
ALCOHOLIC FERMENTATION
SUGAR BREAKS DOWN
INTO CARBON DIOXIDE
AND ETHANOL
 C6H12O6  2 CO2 + 2 C2H5OH
ETHANOL IS THE ACTIVE
INGREDIENT IN WINE,
BEER AND SPIRITS.
THE CARBON DIOXIDE
PRODUCED IN THIS
MANNER CAN BE USED
TO ALLOW BREAD TO
RISE
73
• IN ALCOHOL FERMENTATION, PYRUVATE IS CONVERTED TO ETHANOL IN
TWO STEPS, WITH THE FIRST RELEASING CO2
• ALCOHOL FERMENTATION BY YEAST IS USED IN BREWING, WINEMAKING,
AND BAKING
74
Animation: Fermentation Overview
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Fig. 9-18a
2 ADP + 2 P i
Glucose
2 ATP
Glycolysis
2 Pyruvate
2 NAD+
2 Ethanol
2 NADH
+ 2 H+
2 CO2
2 Acetaldehyde
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(a) Alcohol fermentation
FERMENTATION AND AEROBIC RESPIRATION
COMPARED
• BOTH PROCESSES USE GLYCOLYSIS TO OXIDIZE GLUCOSE AND OTHER
ORGANIC FUELS TO PYRUVATE
• THE PROCESSES HAVE DIFFERENT FINAL ELECTRON ACCEPTORS: AN ORGANIC
MOLECULE (SUCH AS PYRUVATE OR ACETALDEHYDE) IN FERMENTATION AND
O2 IN CELLULAR RESPIRATION
• CELLULAR RESPIRATION PRODUCES 38 ATP PER GLUCOSE MOLECULE;
FERMENTATION PRODUCES 2 ATP PER GLUCOSE MOLECULE
• 3 ANIMALS THAT BREATH THROUGH THEIR BUTTS
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• OBLIGATE ANAEROBES CARRY OUT
FERMENTATION OR ANAEROBIC RESPIRATION
AND CANNOT SURVIVE IN THE PRESENCE OF O2
• YEAST AND MANY BACTERIA ARE FACULTATIVE
ANAEROBES, MEANING THAT THEY CAN
SURVIVE USING EITHER FERMENTATION OR
CELLULAR RESPIRATION (PREFERRED METHOD)
Clostridium tetani
an obligate anaerobe
• IN A FACULTATIVE ANAEROBE, PYRUVATE IS A
FORK IN THE METABOLIC ROAD THAT LEADS TO
TWO ALTERNATIVE CATABOLIC ROUTES
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Fig. 9-19
Glucose
CYTOSOL
Glycolysis
Pyruvate
No O2 present:
Fermentation
O2 present:
Aerobic cellular
respiration
MITOCHONDRION
Ethanol
or
lactate
Acetyl CoA
Citric
acid
cycle
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THE EVOLUTIONARY SIGNIFICANCE OF
GLYCOLYSIS
GLYCOLYSIS OCCURS IN NEARLY ALL ORGANISMS
GLYCOLYSIS PROBABLY EVOLVED IN ANCIENT PROKARYOTES BEFORE THERE
WAS OXYGEN IN THE ATMOSPHERE
IT IS BELIEVED SINCE THE CATABOLIC PATHWAY DOESN’T REQUIRE OTHER
ORGANELLES THAT IT WAS EVOLVED VERY EARLY ON IN HISTORY
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QUESTION:
• CONSIDER THE NAD FORMED DURING GLYCOLYSIS.
• WHAT IS THE FINAL ACCEPTOR FOR ITS ELECTRONS DURING
FERMENTATION?
• WHAT IS THE FINAL ACCEPTOR FOR ITS ELECTRONS DURING AEROBIC
RESPIRATION
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ANSWER:
• A DERIVATIVE OF PYRUVATE LIKE ACETALDEHYDE DURING ALCOHOL
FERMENTATION OR PYRUVATE ITSELF DURING LACTIC ACID
FORMATION
• OXYGEN
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CONCEPT 9.6: GLYCOLYSIS AND THE CITRIC
ACID CYCLE CONNECT TO MANY OTHER
METABOLIC PATHWAYS
• GYCOLYSIS AND THE CITRIC ACID CYCLE ARE MAJOR INTERSECTIONS TO
VARIOUS CATABOLIC AND ANABOLIC PATHWAYS
• WE DON’T EAT A LOT OF FREE GLUCOSE, BUT GET MOST OUR CALORIES
FROM FATS, PROTEINS, SUCROSE, STARCH ETC
• ALL THESE MOLECULES CAN BE USED IN CELLULAR RESPIRATION
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THE VERSATILITY OF CATABOLISM
• CATABOLIC PATHWAYS FUNNEL ELECTRONS FROM MANY KINDS OF
ORGANIC MOLECULES INTO CELLULAR RESPIRATION
• GLYCOLYSIS ACCEPTS A WIDE RANGE OF CARBOHYDRATES
• PROTEINS MUST BE DIGESTED TO AMINO ACIDS;
• AMINO ACIDS WILL GO TO CREATE MORE PROTEINS BUT AMINO GROUPS CAN
FEED GLYCOLYSIS OR THE CITRIC ACID CYCLE (THE AMINO GROUP MUST BE
REMOVED THROUGH DEAMINATION)
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• FATS ARE DIGESTED TO GLYCEROL (USED IN THE INTERMEDIATE
GLYCERALDEHYE-3-PHOSPHATE IN A STEP IN GLYCOLYSIS) AND FATTY ACIDS
(USED IN GENERATING ACETYL COA)
• FATTY ACIDS ARE BROKEN DOWN BY BETA OXIDATION AND YIELD ACETYL
COA (2 CARBON FRAGMENT) AND NADH AND FADH2
• AN OXIDIZED GRAM OF FAT PRODUCES MORE THAN TWICE AS MUCH ATP
AS AN OXIDIZED GRAM OF CARBOHYDRATE
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Fig. 9-20
Proteins
Carbohydrates
Amino
acids
Sugars
Fats
Glycerol
Fatty
acids
Glycolysis
Glucose
Glyceraldehyde-3- P
NH3
Pyruvate
Acetyl CoA
Citric
acid
cycle
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Oxidative
phosphorylation
BIOSYNTHESIS (ANABOLIC PATHWAYS)
•
REVIEW: NOT USUALLY SPONTANEOUS, REQUIRE ENERGY,
•
∆ G IS POSITIVE
•
THE BODY USES SMALL MOLECULES TO BUILD OTHER SUBSTANCES (LIKE AMINO ACIDS USED TO MAKE PROTEINS)
•
THESE SMALL MOLECULES MAY COME DIRECTLY FROM FOOD, FROM GLYCOLYSIS, OR FROM THE CITRIC ACID CYCLE
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ANABOLIC STEROIDS (BECAUSE I’M
THINKING ABOUT IT)
• MIMIC THE AFFECT OF
TESTOSTERONE IN THE BODY
• INCREASE PROTEIN SYNTHESIS
WITH BUILD UP IN BODY TISSUE
RESULTING
• INCREASE IN MALE
CHARACTERISTICS
• PROBLEMS: LIVER DAMAGE, HEART
DAMAGE, HIGH CHOLESTEROL,
HIGH BLOOD PRESSURE
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REGULATION OF CELLULAR RESPIRATION VIA
FEEDBACK MECHANISMS
• FEEDBACK INHIBITION IS THE MOST COMMON MECHANISM FOR CONTROL
• A LOT OF “END PRODUCT” SENDS A MESSAGE TO THE STARTING POINT OR AN
EARLIER INTERMEDIATE STEP TO SLOW DOWN PRODUCTION
• IF ATP CONCENTRATION BEGINS TO DROP, RESPIRATION SPEEDS UP; WHEN
THERE IS PLENTY OF ATP, RESPIRATION SLOWS DOWN (YOUR BODY IS EFFICIENT
AND DOESN’T WANT TO WASTE THIS ENERGY)
• CONTROL OF CATABOLISM IS BASED MAINLY ON REGULATING THE ACTIVITY 89
OF
ENZYMES AT STRATEGIC POINTS IN THE CATABOLIC PATHWAY
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DIABETES- INSULIN RESISTANT TYPE
• INSULIN SIGNALS THE BODY TO REMOVE GLUCOSE FROM THE BLOOD STREAM
AND DELIVER IT TO CELLS
• INSULIN ALSO SPEEDS UP THE CONVERSION OF GLUCOSE TO GLYCOGEN (THE
STORAGE FORM OF CARBS WE USE); INCREASES THE UPTAKE OF AMINO ACIDS
AND THE SYNTHESIS OF PROTEINS
• IF SOMEONE IS INSULIN RESISTANT OR DOESN’T PRODUCE ENOUGH INSULIN
THEN THESE THINGS ACCUMULATE IN THE BLOOD
• AT FIRST THE BETA CELLS WILL INCREASE INSULIN PRODUCTION BUT EVENTUALLY
THE BETA CELLS THAT SECRETE INSULIN CAN’T KEEP UP
• HIGH GLUCOSE CAUSES EXCESSIVE THIRST AND FATIGUE
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INSULIN DEPENDENT DIABETES
• GLUCOSE ACCUMULATES IN THE BLOOD BECAUSE THE PANCREAS
ISN’T PRODUCING ENOUGH INSULIN TO GET THE GLUCOSE INTO THE
CELLS (SO, THIRST AND FATIGUE BECAUSE YOUR BODY DOESN’T DO
CELLULAR RESPIRATION AS EFFICIENTLY)
• THESE PATIENTS INJECT THEMSELVES WITH INSULIN SO THAT THE
GLUCOSE DOES GO INTO THE CELLS AND THE BODY USES IT TO
BREAK DOWN FOR ENERGY
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• HTTP://WWW.YOUTUBE.COM/WATCH?V=GH2P5CMCC0M
• BOZEMAN ON CELL RESPIRATION
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EVOLUTION CONNECTION
• ATP SYNTHASES ARE FOUND IN THE PROKARYOTIC PLASMA
MEMBRANE AND IN MITOCHONDRIA AND CHLOROPLASTS. WHAT
DOES THIS SUGGEST ABOUT THE EVOLUTIONARY RELATIONSHIP OF
THESE EUKARYOTIC ORGANELLES TO PROKARYOTES?
• HOW MIGHT THE AMINO ACID SEQUENCES OF THE ATP SYNTHASES
FROM THE DIFFERENT SOURCES SUPPORT OR REFUTE YOUR
HYPOTHESIS?
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• HAD EVOLUTIONARY ORIGIN IN MITOCHONDRIA AND PLASTIDS WHEN
THEY WERE ORIGINALLY THEIR OWN INDEPENDENT PROKARYOTE
• THESE ANCESTORS WERE CAPABLE OF SYNTHESIZING ATP
• WE CAN SEQUENCE THE AMINO ACIDS FOR SIMILARITIES BETWEEN THE
MITOCHONDRIA, CHLOROPLASTS AND PROKARYOTES IF THEY ARE
HIGHLY CONSERVED IT WOULD SUGGEST COMMON ANCESTRY
• IF THE ENZYMES ARE SIMILAR THIS WOULD SUGGEST COMMON
ANCESTRY TOO
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Fig. 9-21
Glucose
AMP
Glycolysis
Fructose-6-phosphate
–
Stimulates
+
Phosphofructokinase
–
Fructose-1,6-bisphosphate
Inhibits
Inhibits
Pyruvate
ATP
Citrate
Acetyl CoA
Citric
acid
cycle
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Oxidative
phosphorylation
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YOU SHOULD NOW BE ABLE TO:
1.
EXPLAIN IN GENERAL TERMS HOW REDOX REACTIONS ARE INVOLVED IN
ENERGY EXCHANGES
2.
NAME THE THREE STAGES OF CELLULAR RESPIRATION; FOR EACH, STATE
THE REGION OF THE EUKARYOTIC CELL WHERE IT OCCURS AND THE
PRODUCTS THAT RESULT
3.
IN GENERAL TERMS, EXPLAIN THE ROLE OF THE ELECTRON TRANSPORT
CHAIN IN CELLULAR RESPIRATION
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4.
EXPLAIN WHERE AND HOW THE RESPIRATORY ELECTRON TRANSPORT
CHAIN CREATES A PROTON GRADIENT
5.
DISTINGUISH BETWEEN FERMENTATION AND ANAEROBIC RESPIRATION
6.
DISTINGUISH BETWEEN OBLIGATE AND FACULTATIVE ANAEROBES
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