Transcript Bio1A - Lec 10 slides File

Cellular Respiration
Decarboxylation
Kreb’s
Oxidative Phosphorylation
Reading
Photosynthesis
Autotrophs
Chloroplast histology
Light Reactions
Dark Reaction
C-4 & CAM plants
Homework
Ch 9: Cellular Respiration
Ch 10: Photosynthesis
Ch 12 Prequiz
Ch 13 prequiz
Ch 14 Prequiz
Test 1 Postponed to Oct 10
Q&A Wed 10/5
Cell Respiration
Oxidation of C and Reduction of O
Reduction
C6H12O6 + 6 O2

Oxidation
6 CO2 + 6 H2O + Energy
(ATP + heat)
ΔG° = - 686 kcal/mole
But broken down in a
more controlled release
Stepwise oxidation
Each step releases significant energy
Nothing 100% efficient
Fig. 9-5
Electron shuttling by:
H2 + 1/2 O2
1/ O
2 2
2H
(from food via NADH)
2 H+ + 2 e–
Controlled
release of
energy for
synthesis of
ATP
Explosive
release of
heat and light
energy
Flour Mill
explosions
(a) Uncontrolled reaction
1/ O
2 2
(b) Cellular respiration
Fig. 9-6-3
The Stages of Cellular Respiration
Electrons carried
via NADH and
FADH2
Electrons
carried
via NADH
Glycolysis
Pyruvate
Glucose
Citric
acid
cycle
Pyruvate
oxidation
Oxidative
phosphorylation:
electron transport
& chemiosmosis
Mitochondrion
Cytosol
ATP
ATP
ATP
Substrate-level
phosphorylation
Substrate-level
phosphorylation
Oxidative
phosphorylation
Glycolysis
•
•
•
•
Cytosol
Simplest metabolic pathway
Most cells do it
Considered most primitive biochem process
mitochondria not needed
• 10 steps  10 enzymes
Glycolysis : Splitting of sugar
2 phases
Investment Phase
4 ADP & 2 NAD+
2 ATP
Glucose
Payoff phase
2 G3P
(C3)
(C6)
2 ADP
BPG
2Pyruvate
(C3)
4 ATP
2 NADH + H+
Investment Phase
Coupling
C  D
ΔG° = 5 kcal/mol
ATP  ADP + Pi
ΔG° = -7.3kcal/mol
C + ATP  D + ADP + Pi ΔG° = -2.3kcal/mol
E  F
ΔG° = 14 kcal/mol
Cannot be coupled to ATP, but maybe another reaction
G  H
ΔG° = -3 kcal/mol
Can be coupled but probably isn’t because it is already spontaneous
Which of the
following is a
possible ΔG?
a)-4
b)1
c)2
d)3
Which of the following is a possible
ΔG for ONLY:
Pi + Glu  G6P
Remember you coupled
this to ATP hydrolysis
a)-5
b)3
c)8
d)11
ATP  ADP + Pi
ΔG°= -7.3
kcal/mole
ATP + Glu  G6P + ADP
ΔG° < 0
Fig. 9-8
Glucose  CO2
Glycolysis
Kreb’s
ΔG° -686 kcal/mol
Oxidative Phosphorylation
4 ADP & 2 NAD+
2 ATP
Glucose
2 G3P
2 ADP
2Pyruvate
4 ATP
2 NADH + H+
Glucose  Pyruvate ΔG° -140 kcal/mol
Glycolysis : Energy investment phase
Glucose + 2ATP
2 G3P + 2 ADP
Use up 2 ATP because:
Glucose + Pi
2ATP
2 G3P
ΔG is
positive
2 ADP + 2 Pi
•Also “priming” G6P allow more glucose into the cell
& Blocks glucose from leaking out
•2nd ATP Hydrolysis step is essentially irreversible
committing molecule to the rest of glycolysis
How many total ATP are produced
during glycolysis?
Payoff phase
Investment Phase
4 ADP & 2 NAD+
2 ATP
Glucose
a)-2
b)4
c)10
d)32
2 G3P
2 ADP
2Pyruvate
4 ATP
2 NADH + H+
How many NET ATP are
produced during glycolysis?
a)-2
b)2
c)10
d)32
Payoff phase
1st oxidation step
oxidized
•Dehydrogenase
NAD+ involved
Oxidation of C
Coupled to reduction
of NAD+
Glyceraldehyde3-phosphate
2 x
2 NAD+
2 NADH
aka
G3P
GAP
PGAL
6
Triose phosphate
dehydrogenase
2Pi
+ 2 H+
•Large energy release
2 x
1, 3-Bisphosphoglycerate
BPG
For G3P +Pi  BPG?
What is a feasible G?
Remember:
NAD+  NADH + H+
ΔG° = 53 kcal/mole
Glyceraldehyde3-phosphate
2 x
2 NAD+
a)-61
2 NADH
6
Triose phosphate
dehydrogenase
2Pi
+ 2 H+
b)-8
c)-2
d)+40
2 x
1, 3-Bisphosphoglycerate
G3P +Pi  BPG
ΔG° = ?
NAD+  NADH + H+
ΔG° = 53 kcal/mole
G3P + NAD+  BPG + NADH + H+
a)-61
b)-8
c)-2
d)+40
oxidized
R-CHO  R-COOH
NAD+
NADH
ΔG° -10.3 kcal/mol
Only that it is neg is important
Glyceraldehyde3-phosphate
2 x
2 NAD+
2 NADH
6
Triose phosphate
dehydrogenase
2Pi
+ 2 H+
2 x
1, 3-Bisphosphoglycerate
BPG
Fig. 9-9-6
2 NAD+
2 NADH
+ 2 H+
6
Triose phosphate
dehydrogenase
2 Pi
2 1, 3-Bisphosphoglycerate
2 ADP
7
Phosphoglycerokinase
2 ATP
2 1, 3-Bisphosphoglycerate
2 ADP
2
3-Phosphoglycerate
ΔG° 7.3
2 ATP
2
ΔG° -7.3 kcal/mol
7
Phosphoglycerokinase
3-Phosphoglycerate
Overall ΔG° -0.1 kcal/mol
Substrate level phosphorylation
Transfer of a phosphate from substrate to
ADP to generate ATP
R-P + ADP
R
+ ATP
• A smaller amount of ATP is formed in glycolysis and the
citric acid cycle by substrate-level phosphorylation
• Oxidative phosphorylation accounts for almost 90% of
the ATP generated by cellular respiration
Pi + ADP
ATP
Fig. 9-9-9
2 NAD+
Substrate Phosphorylation
6
Triose phosphate
dehydrogenase
2 Pi
2 NADH
+ 2 H+
2 1, 3-Bisphosphoglycerate
2 ADP
7 Phosphoglycerokinase
2 ATP
2
Phosphoenolpyruvate
ΔG° -15 kcal/mol
2 ADP
2
3-Phosphoglycerate
8
Phosphoglyceromutase
2 ATP
2
10
Pyruvate
kinase
2-Phosphoglycerate
9
2 H2O
Enolase
2 Phosphoenolpyruvate
2 ADP
10
Pyruvate kinase
2 ATP
2
2
Pyruvate
Pyruvate
2
Phosphoenolpyruvate
2 ADP
10
Pyruvate kinase
2 ATP
2
Pyruvate
What is a possible free
energy change (ΔG) of
phosphoenolpyruvate to
pyruvate?
PEP  pyruvate + Pi
a)+5 kcal/mole
b)0
c) -5
d)-12
e)None of the above
What is the primary mechanism
of ATP generation in glycolysis?
a)ATP
b)NADP
c) substrate level phosphorylation
d)pyruvate
Which of the following is NOT a
product of glycolysis?
a)ATP
b)NADP
c)Lactic Acid
d)Pyruvate
Lactic acid fermentation
2 ADP + 2 P i
Glucose
2 ATP
Glycolysis
2 NAD+
2 NADH
+ 2 H+
2 Pyruvate
2 Lactate
Lactic acid fermentation
• 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
Why does a cell use fermentation?
a)To produce ATP
b) To produce lactic acid
c)To produce NAD+
d)To produce NADH
Fig. 9-8
How equilibrium affects Respiration
Normally (under aerobic conditions):
•Glucose resupplied
•Pyruvate & NADH used in next step
NADH + H+  NAD+
•ATP used for work
Anaerobic conditions (NO O2):
•Pyruvate & NADH not used (O2 is required)
• “Run out” of NAD+
Net
Glucose
2 ADP + 2 Pi
2 NAD+ + 4 e– + 4 H+
2 Pyruvate + 2 H2O
2 ATP
2 NADH + 2 H+
Alcohol fermentation
2 ADP + 2
Glucose
P
i
2 ATP
Glycolysis
2 Pyruvate
2 NAD+
2 Ethanol
2 NADH
+ 2 H+
2 CO2
2 Acetaldehyde
Many other forms including production of
methane and hydrogen gas
What is the enzyme for alcohol fermentation?
a)Kinase
b)Phosphotase
c)Dehydrogenase
d)protease
?
Pyruvate decarboxylation &
citric acid (or kreb’s) cycle
completes the energy-yielding
oxidation of organic molecules
• In the presence of O2, pyruvate enters the
mitochondrial Matrix
• Before the citric acid cycle can begin, pyruvate
must be converted to acetyl CoA, which links
the cycle to glycolysis
Pyruvate oxidation
Step 1: pyruvate decarboxylation
CYTOSOL
MITOCHONDRION
NAD+
NADH
+ H+
2
1
Pyruvate
3
CO2
Coenzyme A
Acetyl CoA
Transport protein
/ pump
What is the enzyme?
Pyruvate Dehydrogenase
Fig. 9-10
Pyruvate  AcetylCoA is what
kind of reaction?
a)Substrate phosphorylation
b)Oxidative phosphorylation
c)condensation
d)Redox
Pyruvate dehydrogenase is likely
inhibited by:
Consider homeostasis
Consider feedback inhibition
O2 NADH
Glucose
NADH
a)pyruvate
b)ADP
c)ATP
d)O2
pyruvate
ATP
CO2
ATP is a competitive inhibitor, what will
happen to the enzyme kinetics of
pyruvate dehyrogenase as ATP builds up?
a)Vmax will go up
b)Vmax will go down
c)Km will shift right
d)Km will shift left
Pyruvate oxidation
Step 1: pyruvate decarboxylation
CYTOSOL
MITOCHONDRION
NAD+
NADH
+ H+
2
1
Pyruvate
3
CO2
Coenzyme A
Acetyl CoA
Transport protein
Oxidation  produces NADH
CoA carries 2 carbon unit to citric acid cycle
CO2 released
Fig. 9-10
AcetylCoA is starting material for Krebs cycle
• The citric acid cycle, also called the Krebs cycle,
takes place within the mitochondrial matrix
(except succinate dehydrogenase which is loosely
associated with inside membrane)
• The cycle oxidizes organic fuel derived from
pyruvate, generating 1 ATP, 3 NADH, and 1
FADH2 per turn
• Complete oxidation of glucose  CO2
Fig. 9-12-8
CoA for next pyruvate
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
ADP
ATP
Pi
Succinyl
CoA
NADH
+ H+
CO2
Pyruvate
CO2
NAD+
NADH
+ H+
Glycolysis
1 glucose  2 Pyruvates
2 NADH & 2ATP
CoA
Acetyl CoA
CoA
Pyruvate Decarboxylation
2 pyruvate  2 CO2
2 Acetyl CoA
2 NADH
Kreb’s
CoA
Citric
acid
cycle
FADH2
2 CO2
3 NAD+
3 NADH
+ 3 H+
FAD
ADP + P i
ATP
2 Acetyl  2 turns
1 turn 
•2 CO2
•3 NADH + H+
•1FADH2
•ATP
Total
4 CO2
6 NADH
2 FADH2
2 ATP
Before the krebs cycle, most of the
free energy from glucose was in:
a)Pyruvate
b)ATP
c)NADH
d)FADH
After the krebs cycle, most of the
free energy from glucose was in:
a)CO2
b)ATP
c)NADH
d)FADH
Fig. 9-8
Glucose  CO2
Glycolysis
Kreb’s
ΔG° -686 kcal/mol
Oxidative Phosphorylation
4 ADP & 2 NAD+
2 ATP
Glucose
2 G3P
2 ADP
2Pyruvate
4 ATP
2 NADH + H+
Glucose  Pyruvate ΔG° -140 kcal/mol
Lactic acid fermentation
2 ADP + 2 P i
Glucose
2 ATP
Glycolysis
2 NAD+
2 NADH
+ 2 H+
2 Pyruvate
2 Lactate
Lactic acid fermentation
• 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
Why does a cell use fermentation?
a)To produce ATP
b) To produce lactic acid
c)To produce NAD+
d)To produce NADH
Fig. 9-8
How equilibrium affects Respiration
Normally (under aerobic conditions):
•Glucose resupplied
•Pyruvate & NADH used in next step
NADH + H+  NAD+
•ATP used for work
Anaerobic conditions (NO O2):
•Pyruvate & NADH not used (O2 is required)
• “Run out” of NAD+
Net
Glucose
2 ADP + 2 Pi
2 NAD+ + 4 e– + 4 H+
2 Pyruvate + 2 H2O
2 ATP
2 NADH + 2 H+
Alcohol fermentation
2 ADP + 2
Glucose
P
i
2 ATP
Glycolysis
2 Pyruvate
2 NAD+
2 Ethanol
2 NADH
+ 2 H+
2 CO2
2 Acetaldehyde
Many other forms including production of
methane and hydrogen gas
What is the enzyme for alcohol fermentation?
a)Kinase
b)Phosphotase
c)Dehydrogenase
d)protease
?
Pyruvate decarboxylation &
citric acid (or kreb’s) cycle
completes the energy-yielding
oxidation of organic molecules
• In the presence of O2, pyruvate enters the
mitochondrial Matrix
• Before the citric acid cycle can begin, pyruvate
must be converted to acetyl CoA, which links
the cycle to glycolysis
Pyruvate oxidation
Step 1: pyruvate decarboxylation
CYTOSOL
MITOCHONDRION
NAD+
NADH
+ H+
2
1
Pyruvate
3
CO2
Coenzyme A
Acetyl CoA
Transport protein
/ pump
What is the enzyme?
Pyruvate Dehydrogenase
Fig. 9-10
Coenzyme A
Carries acetyl groups
From vit B5
Pyruvate  AcetylCoA is what
kind of reaction?
a)Substrate phosphorylation
b)Oxidative phosphorylation
c)condensation
d)Redox
Pyruvate dehydrogenase is likely
inhibited by:
Consider homeostasis
Consider feedback inhibition
O2 NADH
Glucose
NADH
a)pyruvate
b)ADP
c)ATP
d)O2
pyruvate
ATP
CO2
ATP is a competitive inhibitor, what will
happen to the enzyme kinetics of
pyruvate dehyrogenase as ATP builds up?
a)Vmax will go up
b)Vmax will go down
c)Km will shift right
d)Km will shift left
Pyruvate oxidation
Step 1: pyruvate decarboxylation
CYTOSOL
MITOCHONDRION
NAD+
NADH
+ H+
2
1
Pyruvate
3
CO2
Coenzyme A
Acetyl CoA
Transport protein
Oxidation  produces NADH
CoA carries 2 carbon unit to citric acid cycle
CO2 released
Fig. 9-10
AcetylCoA is starting material for Krebs cycle
• The citric acid cycle, also called the Krebs cycle,
takes place within the mitochondrial matrix
(except succinate dehydrogenase which is loosely
associated with inside membrane)
• The cycle oxidizes organic fuel derived from
pyruvate, generating 1 ATP, 3 NADH, and 1
FADH2 per turn
• Complete oxidation of glucose  CO2
Fig. 9-12-8
CoA for next pyruvate
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
ADP
ATP
Pi
Succinyl
CoA
NADH
+ H+
CO2
Pyruvate
CO2
NAD+
NADH
+ H+
Glycolysis
1 glucose  2 Pyruvates
2 NADH & 2ATP
CoA
Acetyl CoA
CoA
Pyruvate Decarboxylation
2 pyruvate  2 CO2
2 Acetyl CoA
2 NADH
Kreb’s
CoA
Citric
acid
cycle
FADH2
2 CO2
3 NAD+
3 NADH
+ 3 H+
FAD
ADP + P i
ATP
2 Acetyl  2 turns
1 turn 
•2 CO2
•3 NADH + H+
•1FADH2
•ATP
Total
4 CO2
6 NADH
2 FADH2
2 ATP
Before the krebs cycle, most of the
free energy from glucose was in:
a)Pyruvate
b)ATP
c)NADH
d)FADH
After the krebs cycle, most of the
free energy from glucose was in:
a)CO2
b)ATP
c)NADH
d)FADH
oxidative phosphorylation
1. electron transport
& 2. ATP synthesis
• Following glycolysis and the citric acid cycle,
NADH and FADH2 account for most of the energy
extracted from food (Oxidation products)
• These two electron carriers donate electrons to
the electron transport chain, which powers ATP
synthesis via oxidative phosphorylation
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
• The carriers alternate reduced and oxidized
states as they accept and donate electrons
Coenzyme Q = Ubiquinone (UQ)
hydrophobic – located in membrane / Cristae
Like NAD+ CoQ is an electron carrier
oxidized
UQ + 2H+ + 2e-
reduced

UQH2
Cytochromes
-a, -a3, -b, -c, -c1
Heme (with iron) -containing proteins complexes
also undergo Redox
Diff proteins with diff hemes
Free energy of electrons gradually drops
• Electrons drop in free energy
as they go down the chain
• and are finally passed to O2
to give:
2H+ + 2e- + O2  H2O
CoQ
• Does NOT directly generate ATP
• chain’s function is to break the
large free-energy drop into smaller
steps that release energy in
manageable amounts
Orientation does NOT
match true location
40-50
proteins
Complexes are H+-pumps
Where does the energy for complex I proton
pump come from (most directly):
a)Pyruvate
b)ATP
c)NADH
d)FADH
NADH oxidation
INTERMEMBRANE SPACE
H+
ATP synthase
Stator
Rotor
Internal
rod
Catalytic
knob
ADP
+
P
i
ATP
MITOCHONDRIAL MATRIX
Fig. 9-14
H+
Chemiosmosis:
The Energy-Coupling Mechanism
Electron transport is coupled to ATP synthesis
• Electron transfer in the electron transport chain
causes proteins to pump H+ from the mitochondrial
matrix to the intermembrane space
• H+ then moves back across the membrane, passing
through channels in ATP synthase
• ATP synthase uses the exergonic flow of H+ to drive
phosphorylation of ATP
• This is an example of chemiosmosis, the use of
energy in a H+ gradient to drive cellular work
Dinitrophenol (DNP)
uncoupler
Allows H+ to diffuse
Fig. 9-17
• Gycolysis and the citric acid cycle
are major intersections to
various metabolic pathways
• Catabolic pathways funnel many
organic molecules into cellular
respiration
- Glycolysis accepts a wide
range of carbohydrates
- Proteins must be digested to
amino acids; amino groups
can feed glycolysis or the
citric acid cycle
Fig. 9-20
- Fats are digested to glycerol (used in glycolysis)
and fatty acids (used in generating acetyl CoA)
• Fatty acids are broken down by beta oxidation and
yield acetyl CoA
• An oxidized gram of fat produces more than twice as
much ATP as an oxidized gram of carbohydrate
The Process That Feeds the Biosphere
• Photosynthesis is the process that converts
solar energy into chemical energy
• Directly or indirectly, photosynthesis nourishes
almost the entire living world
Photosynthesis
6 CO2 + 6 H2O + Light energy  C6H12O6 + 6 O2
6 CO2 + 12 H2O + Light energy  C6H12O6 + 6 O2 + 6 H2O
Reactants:
Products:
6 CO2
C6H12O6
12 H2O
6 H2O
6 O2
Remove H = oxidized
Add H = reduced
Light is the driving factor
• electromagnetic energy, aka electromagnetic radiation
• behaves as though it consists of discrete particles,
called photons
• travels in rhythmic waves
– Wavelength is the distance between crests of waves
– determines the type of electromagnetic energy
A pigment abosrbs light in the blue and
green spectrum. What will it look like?
a) Blue
b) Green
c) Blue / Green
d) Red / yellow
Phycourobilin is orange. What colors does
it absorb?
a) Blue / Green
b) ultraviolet
c) Red
d) Red / yellow
10–5 nm 10–3 nm
103 nm
1 nm
Gamma
X-rays
rays
UV
106 nm
Infrared
1m
(109 nm)
Microwaves
103 m
Radio
waves
Visible light
380
450
500
Shorter wavelength
Higher energy
550
600
650
700
750 nm
Longer wavelength
Lower energy
Photosynthetic Pigments: The
Light Receptors
• Pigments - substances that absorb visible light
• Different pigments absorb different wavelengths
• Wavelengths that are not absorbed are
reflected or transmitted
ex: Leaves appear green because chlorophyll reflects
and transmits green light
Fig. 10-7
Light
Reflected
light
Chloroplast
Absorbed
light
Granum
Transmitted
light
Fig. 10-9
RESULTS
Chlorophyll a
Chlorophyll b
Carotenoids
(a) Absorption spectra
400
500
600
700
Wavelength of light (nm)
(b) Action spectrum
Aerobic bacteria
Filament
of alga
(c) Engelmann’s
experiment
400
500
600
700
Fig. 10-10
CH3
CHO
in chlorophyll a
in chlorophyll b
Porphyrin ring:
light-absorbing
“head” of molecule;
note magnesium
atom at center
Hydrocarbon tail:
interacts with hydrophobic
regions of proteins inside
thylakoid membranes of
chloroplasts
Charge separation - Depart
to a nearby electron acceptor
Energy of electron
e–
Excited
state
Heat
Photon
pigments
(a) Excitation of molecule
Photon
(fluorescence)
Ground
state
(b) Fluorescence
Fig. 10-11
The Two Stages of Photosynthesis
• light reactions (the photo part)
• Calvin cycle (the synthesis part)
H2 O
Light reactions (thylakoids):
– Split H2O
– Release O2
– Reduce NADP+ to NADPH
– Generate ATP from ADP by
photophosphorylation
Light
NADP+
ADP
P
Light
Reactions
Chloroplast
i
thylakoid membrane: 2 photosystems
PS II & PS I
Each Photosystem:
• Chlorophyll a essential
• Accessory pigments
(technically nonessential)
Broaden and protect
 Although PS II
reaction-center chlorophyll a best
at absorbing 680nm (called P680)
Photosystem can absorb more
PS I (P700)