Transcript O - bio-brainstorm

Cellular Respiration
Harvesting Chemical Energy
ATP
AP Biology
2006-2007
Harvesting stored energy
 Glucose is the model
respiration

catabolism of glucose to produce ATP
glucose + oxygen  energy + water + carbon
dioxide
C6H12O6 +
6O2
 ATP + 6H2O + 6CO2 + heat
COMBUSTION = making a lot of heat energy
by burning fuels in one step
fuel
AP Biology
carbohydrates)
RESPIRATION = making ATP (& some heat)
by burning fuels in many small steps
ATP
enzymes
O2
ATP
O2
CO2 + H2O + ATP (+ heat)
glucose
CO2 + H2O + heat
How do we harvest energy from fuels?
 Digest large molecules into smaller ones

break bonds & move electrons from one
molecule to another
 as electrons move they “carry energy” with them
 that energy is stored in another bond,
released as heat or harvested to make ATP
loses e-
gains e-
+
oxidized
reduced
+
+
eoxidation
AP Biology
e-
–
ereduction
redox
How do we move electrons in biology?
 Moving electrons in living systems

electrons cannot move alone in cells
 electrons move as part of H atom
e
p
 move H = move electrons
loses e-
gains e-
oxidized
+
+
oxidation
reduced
+
–
H
reduction
H
oxidation
C6H12O6 +
AP Biology
H e-
6O2
 6CO2 + 6H2O + ATP
reduction
Coupling oxidation & reduction
 REDOX reactions in respiration

release energy as breakdown organic molecules
 break C-C bonds
 strip off electrons from C-H bonds by removing H atoms
 C6H12O6  CO2 = the fuel has been oxidized
 electrons attracted to more electronegative atoms
 in biology, the most electronegative atom?
 O2  H2O = oxygen has been reduced

O
couple REDOX reactions &
2
use the released energy to synthesize ATP
oxidation
C6H12O6 +
AP Biology
6O2
 6CO2 + 6H2O + ATP
reduction
Oxidation & reduction
 Oxidation
 Reduction
adding O
 removing H
 loss of electrons
 releases energy
 exergonic

removing O
 adding H
 gain of electrons
 stores energy
 endergonic

oxidation
C6H12O6 +
6O2
 6CO2 + 6H2O + ATP
reduction
AP Biology
like $$
in the bank
Moving electrons in respiration
 Electron carriers move electrons by
shuttling H atoms around
 NAD+  NADH (reduced)
 FAD+2  FADH2 (reduced)
NAD+
nicotinamide
Vitamin B3
niacin
O–
O – P –O
O
phosphates
O–
O – P –O
O
AP Biology
H
reducing power!
NADH
O
H H
C NH2
N+
+
adenine
ribose sugar
C NH2
reduction
O–
–
–
oxidation O P O
O
O–
O – P –O
O
carries electrons as
H
O
a reduced molecule
N+
How efficient!
Build once,
use many ways
Overview of cellular respiration
 3 metabolic stages

Anaerobic respiration
1. Glycolysis
 respiration without O2
 in cytosol

Aerobic respiration
 respiration using O2
 in mitochondria
2. Krebs cycle
3. Electron transport chain
C H O6 +
AP Biology
6 12
6O2
 ATP + 6H2O + 6CO2 (+ heat)
Cellular Respiration
Stage 1:
Glycolysis
AP Biology
2007-2008
Glycolysis
 Breaking down glucose

“glyco – lysis” (splitting sugar)
glucose      pyruvate
2x 3C
6C

ancient pathway which harvests energy
 where energy transfer first evolved
 transfer energy from organic molecules to ATP
 still is starting point for ALL cellular respiration

but it’s inefficient
 generate only 2 ATP for every 1 glucose

occurs in cytosol
AP Biology
That’s not enough
ATP for me!
In the
cytosol?
Why does
that make
evolutionary
sense?
Evolutionary perspective
 Prokaryotes

first cells had no organelles
Enzymes
of glycolysis are
“well-conserved”
 Anaerobic atmosphere


life on Earth first evolved without free oxygen (O2)
in atmosphere
energy had to be captured from organic molecules
in absence of O2
 Prokaryotes that evolved glycolysis are ancestors
of all modern life

AP Biology
ALL cells still utilize glycolysis
You mean
we’re related?
Do I have to invite
them over for
the holidays?
Overview
glucose
C-C-C-C-C-C
10 reactions
enzyme
2 ATP
enzyme
2 ADP
convert
fructose-1,6bP
glucose (6C) to
P-C-C-C-C-C-C-P
enzyme
enzyme
2 pyruvate (3C)
enzyme
DHAP
G3P
 produces:
4 ATP & 2 NADH P-C-C-C C-C-C-P
2H
 consumes:
2Pi enzyme
2 ATP
enzyme
 net yield:
2Pi
enzyme
2 ATP & 2 NADH

DHAP = dihydroxyacetone phosphate
AP Biology
G3P
= glyceraldehyde-3-phosphate
pyruvate
C-C-C
2 NAD+
2
4 ADP
4 ATP
Glycolysis summary
endergonic
invest some ATP
ENERGY INVESTMENT
-2 ATP
ENERGY PAYOFF
G3P
C-C-C-P
4 ATP
exergonic
harvest a little
ATP & a little NADH
like $$
in the
bank
NET YIELD
AP Biology
net yield
2 ATP
2 NADH
1st half of glycolysis (5 reactions)
Glucose “priming”

get glucose ready
to split
 phosphorylate
CH2 O
O
P
Glucose 6-phosphate
2
P O
ADP
CH2 O
O
P
CH2
CH2
CH2OH
O
Fructose 1,6-bisphosphate
O CH2
C
4,5 aldolase
isomerase
O Dihydroxyacetone
CH2OH phosphate
Glyceraldehyde 3
-phosphate (G3P)
Pi
NAD+
Pi
6
glyceraldehyde
NADH
NADH
3-phosphate
P
dehydrogenase
1,3-Bisphosphoglycerate 1,3-Bisphosphoglycerate
(BPG)
(BPG)
H
C
O
CHOH
CH2 O
NAD+
AP Biology
O
Fructose 6-phosphate
3
ATP
phosphofructokinase
split destabilized
glucose
P
ADP
phosphoglucose
isomerase
glucose
 molecular
rearrangement

CH2OH
Glucose
1
ATP
hexokinase
O
P
O
CHOH
CH2 O
P
O
P
2nd half of glycolysis (5 reactions)
DHAP
P-C-C-C
Energy Harvest

NADH production





G3P donates H
oxidizes the sugar
reduces NAD+
NAD+  NADH
NAD+
Pi
phosphorylation”
 ADP  ATP
AP Biology
NAD+
NADH
7
phosphoglycerate
kinase
ADP
ATP
3-Phosphoglycerate
(3PG)
ADP
ATP
3-Phosphoglycerate
(3PG)
8
phosphoglyceromutase
2-Phosphoglycerate
(2PG)
Phosphoenolpyruvate
(PEP)
CHOH
CH2
O P
C O
H C O
CH2OH
P
OH2O
Phosphoenolpyruvate
(PEP)
10
pyruvate kinase
ADP
ATP
Pyruvate
C
C
O
O
CH2
OC
ATP
Pyruvate
OC
O-
2-Phosphoglycerate
(2PG)
9
enolase
H2O
ADP
Payola!
Finally some
ATP!
Pi
6
NADH
ATP production
 G3P    pyruvate
 PEP sugar donates P
 “substrate level
G3P
C-C-C-P
O
C O
CH3
P
Substrate-level Phosphorylation
 In the last steps of glycolysis, where did
the P come from to make ATP?

9
the sugar substrateH O(PEP) enolase
OH2O
2
P is transferred
from PEP to ADP
kinase enzyme
ADP  ATP
AP Biology
Phosphoenolpyruvate
(PEP)
ADP
Phosphoenolpyruvate
(PEP)
10
pyruvate kinase
Pyruvate
I get it!
The Pi came
directly from
the substrate!
Pyruvate
C
CH2
O
O
OC
ATP
ATP
ATP
ADP
C
O
C O
CH3
P
Energy accounting of glycolysis
2 ATP
2 ADP
glucose      pyruvate
2x 3C
6C
4 ADP
4 ATP
2 NAD+
2
 Net gain = 2 ATP + 2 NADH


All that work!
And that’s all
I get?
But
glucose has
so much more
to give!
some energy investment (-2 ATP)
small energy return (4 ATP + 2 NADH)
AP 1Biology
6C sugar  2 3C sugars
Cellular Respiration
Stage 2:
Citric Acid Cycle or
Krebs Cycle
AP Biology
2006-2007
Glycolysis is only the start
 Glycolysis
glucose      pyruvate
6C
2x 3C
 Pyruvate has more energy to yield



3 more C to strip off (to oxidize)
if O2 is available, pyruvate enters mitochondria
enzymes of Krebs cycle complete the full
oxidation of sugar to CO2
pyruvate       CO2
AP Biology
3C
1C
Cellular respiration
AP Biology
Mitochondria — Structure
 Double membrane energy harvesting organelle


smooth outer membrane
highly folded inner membrane
 cristae

intermembrane space
 fluid-filled space between membranes

matrix
 inner fluid-filled space


DNA, ribosomes
enzymes
 free in matrix &
What cells would have
AP
Biology
a lot
of mitochondria?
outer
intermembrane
membrane
inner
membrane-bound space
membrane
cristae
matrix
mitochondrial
DNA
Mitochondria – Function
Oooooh!
Form fits
function!
Dividing mitochondria
Membrane-bound proteins
Who else divides like that? Enzymes & permeases
bacteria!
What does this tell us about
the evolution of eukaryotes?
Endosymbiosis!
AP Biology
Advantage of highly folded inner
membrane?
More surface area for membranebound enzymes & permeases
Oxidation of pyruvate
 Pyruvate enters mitochondrial matrix
[
2x pyruvate    acetyl CoA + CO2
3C
2C
1C
NAD
Where
does the
CO2 go?
Exhale!
3 step oxidation process
 releases 2 CO2 (count the carbons!)
 reduces 2 NAD  2 NADH (moves e )
 produces 2 acetyl CoA


Acetyl CoA enters Krebs cycle
AP Biology
]
Pyruvate oxidized to Acetyl CoA
reduction
NAD+
Pyruvate
C-C-C
[
Coenzyme A
CO2
Acetyl CoA
C-C
oxidation
2 x Yield = 2C sugar + NADH + CO2
AP Biology
]
Citric Acid cycle
1937 | 1953
 aka Krebs Cycle
in mitochondrial matrix
 8 step pathway

Hans Krebs
 each catalyzed by specific enzyme
1900-1981
 step-wise catabolism of 6C citrate molecule
 Evolved later than glycolysis

does that make evolutionary sense?
 bacteria 3.5 billion years ago (glycolysis)
 free O2 2.7 billion years ago (photosynthesis)
 eukaryotes 1.5 billion years ago (aerobic
AP Biology
respiration = organelles  mitochondria)
Count the carbons!
pyruvate
3C
2C
6C
4C
This happens
twice for each
glucose
molecule
4C
citrate
oxidation
of sugars
4C
6C
CO2
x2
4C
AP Biology
acetyl CoA
5C
4C
CO2
Count the electron carriers!
pyruvate
3C
6C
4C
NADH
This happens
twice for each
glucose
molecule
2C
4C
citrate
reduction
of electron
carriers
x2
4C
FADH2
4C
AP Biology
acetyl CoA
ATP
CO2
NADH
6C
CO2
NADH
5C
4C
CO2
NADH
Whassup?
So we fully
oxidized
glucose
C6H12O6

CO2
& ended up
with 4 ATP!
What’s the
point?
AP Biology
Electron Carriers = Hydrogen Carriers
H+
 Citric Acid cycle
produces large
quantities of
electron carriers
NADH
 FADH2
 go to Electron
Transport Chain!

AP Biology
What’s so
important about
electron carriers?
H+
H+
H+
+
H+ H H+
H+
ADP
+ Pi
ATP
H+
Energy accounting of Citric Acid cycle
4 NAD + 1 FAD
4 NADH + 1 FADH2
2x pyruvate          CO2
3C
3x 1C
1 ADP
1 ATP
ATP
Net gain = 2 ATP
= 8 NADH + 2 FADH2
AP Biology
Value of Citric Acid cycle?
 If the yield is only 2 ATP then how was the
Citric Acid cycle an adaptation?

value of NADH & FADH2
 electron carriers & H carriers
 reduced molecules move electrons
 reduced molecules move H+ ions
 to be used in the Electron Transport Chain
like $$
in the
bank
AP Biology