Download L7c RESPIRATION Ch9 etc regulation

http://www.youtube.com/watch?v=VCpNk92uswY
What’s the
point?
Cellular Respiration
The point
Stage 4: is to make
ATP!
Electron Transport
Chain
ATP
AP Biology
2013-2014
Cellular respiration
AP Biology
ATP accounting so far…
 Glycolysis  2 ATP
 Kreb’s cycle  2 ATP
 Life takes a lot of energy to run, need to
extract more energy than 4 ATP!
Even we
need a lot
more ATP!
AP Biology
There’s got to be a better way!
I need a lot
more ATP!
A working muscle recycles over
10 million ATPs per second
There is a better way!
 Electron Transport Chain

series of proteins built into
inner mitochondrial membrane
 along cristae
 transport proteins & enzymes
transport of electrons down ETC linked to
pumping of H+ to create H+ gradient
 yields ~36 ATP from 1 glucose!
 only in presence of O 2 (aerobic respiration)

AP Biology
That
sounds more
like it!
O2
Mitochondria
 Double membrane
outer membrane
 inner membrane

 highly folded cristae
 enzymes & transport
proteins

intermembrane space
 fluid-filled space
between membranes
AP Biology
Oooooh!
Form fits
function!
Electron Transport Chain
Inner
mitochondrial
membrane
Intermembrane space
C
Q
NADH
dehydrogenase
cytochrome
bc complex
cytochrome c
oxidase complex
Mitochondrial matrix
AP Biology
Q = ubiquinone c = cytochrome c
Remember the Electron Carriers?
Glycolysis
glucose
Krebs cycle
G3P
2 NADH
2x
=2
8 NADH
2 FADH2
Time to
break open
the piggybank!
x2 = 6
AP Biology
Electron Transport Chain
H+
H+
H+
H+
H  e- + H+
H+
C
e–
NAD+
NADH
dehydrogenase
intermembrane
space
inner
mitochondrial
membrane
e–
H
FADH2
H+
e–
Q
AP Biology
H+
H+
NADH H
H+
Building proton gradient!
NADH  NAD+ + H
e
p
H+
FAD
2H+ +
cytochrome
bc complex
1
2
O2
H 2O
cytochrome c
oxidase complex
mitochondrial
matrix
What powers the proton (H+) pumps?…
e– e–
NADH  NAD+ + H
Stripping H from Electron Carriers
 Electron carriers pass electrons & H+ to ETC


H cleaved off NADH & FADH2
electrons stripped from H atoms  H+ (protons)
 electrons passed from one electron carrier to next in
mitochondrial membrane (ETC)
 flowing electrons = energy to do work

H  e- + H+
transport proteins in membrane pump H+ (protons)
across inner membrane to intermembrane space
TA-DA!!
Moving electrons
do the work!
H+
+
H+
+
H+
H
H
H
H+
+
H+ H
+
H+ H H+
H+
C
Q
e–
NADH
AP Biology
+
H+
FADH2
NAD+
NADH
dehydrogenase
e–
e–
FAD
2H+
cytochrome
bc complex
+
1
2
O2
H2O
cytochrome c
oxidase complex
ADP
+ Pi
ATP
H+
e
p
http://www.johnkyrk.com/mitochondrion.html
But what “pulls” the
electrons down the ETC?
H2O
O2
AP Biology
electrons
flow downhill
to O2
oxidative phosphorylation
Electron transport chain
 Consists of several protein complexes
AP Biology
Aren’t you glad you do not have to memorize this??
http://www.youtube.com/watch?v=QXhBJycQ7y0
http://www.youtube.com/watch?v=_lhVIbifKGU
Electrons flow downhill
 Electrons move in steps from
carrier to carrier downhill to oxygen
each carrier more electronegative
 controlled oxidation
 controlled release of energy

make ATP
instead of
fire!
AP Biology
Figure 9.13
NADH
50
2 e
NAD
FADH2
Free energy (G) relative to O2 (kcal/mol)
2 e
40
FMN
Fe S
Fe S
II
Q
III
Cyt b
30
Multiprotein
complexes
FAD
I
Fe S
Cyt c1
IV
Cyt c
Cyt a
Cyt a3
20
10
2 e
(originally from
NADH or FADH2)
0
http://media.pearsoncmg.com/bc/bc_0media_bio/de
mo/bioflix/bf_cellularrespiration_demo.html
2 H + 1/2 O2
H2 O
http://www.youtube.com/watch?v=-zsEepV0N-I
We did it!
 Set up a H+
“proton-motive” force
H+
H+
H+
gradient
 Allow the protons
to flow through
ATP synthase
 Synthesizes ATP
ADP + Pi  ATP
Are we
there yet?
AP Biology
H+
H+
H+
H+
H+
ADP + Pi
ATP
H+
Chemiosmosis:
The Energy-Coupling Mechanism
 The diffusion of ions across a membrane

build up of proton gradient just so H+ could flow
through ATP synthase enzyme to build ATP
 Electron transfer in the etc causes



Chemiosmosis
links the
Electron
Transport
Chain to ATP
synthesis
proteins to pump H+ from the
mitochondrial matrix to the
intermembrane space
H+ then moves back across the
membrane, passing through the
ATP synthase
ATP synthase uses the exergonic
flow of H+ to drive phosphorylation
of ADP to ATP
This is an example of
chemiosmosis, the use of energy in
a H+ gradient to drive cellular work
AP Biology
So that’s
the point!
1961 | 1978
Peter Mitchell
 Proposed chemiosmotic hypothesis

revolutionary idea at the time
proton motive force
1920-1992
AP Biology
Pyruvate from
cytoplasm
Inner
mitochondrial H+
membrane
H+
Intermembrane
space
Electron
transport
C system
Q
NADH
e-
1. Electrons are harvested
and carried to the
Acetyl-CoA
transport system.
NADH
e-
Krebs
cycle
FADH2
e-
2. Electrons
provide energy
to pump
protons across
the membrane.
e-
H2O
3. Oxygen joins
with protons to
form water.
1 O
2 +2
2H+
O2
H+
CO2
ATP
Mitochondrial
matrix
AP Biology
H+
ATP
ATP
4. Protons diffuse back in
down their concentration
gradient, driving the
synthesis of ATP.
H+
ATP
synthase
Cellular respiration
2 ATP
AP Biology
+
2 ATP
+
~36 ATP
Summary of cellular respiration
C6H12O6 + 6O2







 6CO2 + 6H2O + ~40 ATP
Where did the glucose come from?
Where did the O2 come from?
Where did the CO2 come from?
Where did the CO2 go?
Where did the H2O come from?
Where did the ATP come from?
What else is produced that is not listed
in this equation?
 Why do we breathe?
AP Biology
Taking it beyond…
 What is the final electron acceptor in
H+
H+
H+
C
Q
Electron Transport Chain?e
e–
e–
–
NADH
O2
FADH2
NAD+
NADH
dehydrogenase
FAD
2H+ +
cytochrome
bc complex
1
2
O2
H2O
cytochrome c
oxidase complex
 So what happens if O2 unavailable?
 ETC backs up
nothing to pull electrons down chain
 NADH & FADH2 can’t unload H

AP Biology
 ATP production ceases
 cells run out of energy
 and you die!
Beyond glucose: Other carbohydrates
 Glycolysis accepts a wide range of
carbohydrates fuels

polysaccharides    glucose
hydrolysis
 ex. starch, glycogen

other 6C sugars    glucose
modified
 ex. galactose, fructose
AP Biology
Beyond glucose: Proteins
 Proteins  
   amino acids
hydrolysis
waste
H O
H
| ||
N —C— C—OH
|
H
R
amino group =
waste product
excreted as
ammonia, urea,
or uric acid
AP Biology
glycolysis
Krebs cycle
carbon skeleton =
enters glycolysis
or Krebs cycle at
different stages
Beyond glucose: Fats
 Fats  hydrolysis
    glycerol & fatty acids
glycerol (3C)   PGAL   glycolysis
 fatty acids  2C acetyl  acetyl  Krebs
groups
coA
cycle

glycerol
enters
glycolysis
as
AP PGAL
Biology
fatty acids
enter
Krebs cycle
as acetyl CoA
Carbohydrates vs. Fats
 Fat generates 2x ATP vs. carbohydrate
more C in gram of fat
 more O in gram of carbohydrate

 so it’s already partly oxidized
fat
carbohydrate
AP Biology
Metabolism
 Coordination of
digestion & synthesis

by regulating enzyme
 Digestion

digestion of
carbohydrates, fats &
proteins
 all catabolized through
same pathways
 enter at different points

AP Biology
cell extracts energy
from every source
CO2
Metabolism
 Coordination of digestion &
synthesis

by regulating enzyme
 Synthesis


enough energy?
build stuff!
cell uses points in glycolysis &
Krebs cycle as links to
pathways for synthesis
 run the pathways “backwards”
 eat too much fuel, build fat
pyruvate 
 glucose
Krebs cycle
intermediaries
AP
Biology
acetyl
CoA

amino
acids
  fatty acids
Cells are
versatile &
thrifty
METABOLISM
 Chapter 8
An Introduction to
Metabolism
Metabolism = total of
an organism’s
chemical reactions
AP Biology
Glycan Metabolism
Lipid
Metabolism
AP Biology
Nucleotide
Metabolism
Carbohydrate
Metabolism
Amino Acid
Metabolism
Cofactors
& Vitamins
Control of
Respiration
Feedback
Control
AP Biology
2005-
Feedback Inhibition
 Regulation & coordination of production


production is self-limiting
final product is inhibitor of earlier step
 allosteric inhibitor of earlier enzyme

no unnecessary accumulation of product






ABCDEFG
1
2
3
4
5
6
X
enzyme enzyme enzyme enzyme enzyme enzyme
AP Biology
allosteric inhibitor of enzyme 1
Respond to cell’s needs
 Key points of control

phosphofructokinase
 allosteric regulation of
enzyme
 “can’t turn back” step
before splitting glucose
 AMP & ADP stimulate
 ATP inhibits
 citrate inhibits
Why is this regulation important?
Balancing act:
availability of raw materials vs.
energy
AP
Biologydemands vs. synthesis
Regulation
 Feedback mechanisms
help regulate cellular
respiration
Ex. Feedback
inhibition
 Phosphofructokinase
(PFK) is the major
enzyme in glycolysis
that is controlled
 ATP, Citrate inhibits
 ADP, AMP stimulates

AP Biology
Versatility
 Glucose is not the only
fuel that can be used in
cellular respiration
 Other biomolecules
can be converted into
intermediates and used
in cellular respiration
AP Biology
What’s the
point?
The point
is to make
ATP!
ATP
AP Biology
2013-2014