Transcript Predators & Prey

glucose
C-C-C-C-C-C
2 ATP
OVERVIEW
2 ADP
• 10 reactions
fructose-1,6bP
P-C-C-C-C-C-C-P
DHAP
P-C-C-C
G3P
C-C-C-P
2Pi
2H
2 NAD+
2
2Pi
pyruvate
C-C-C
4 ADP
4 ATP
• Convert
glucose (6C)
to 2 pyruvate
(3C)
• Produces: 4
ATP & 2
NADH
• Consumes: 2
ATP
• Net yield: 2
ATP & 2
NADH
DHAP = dihydroxyacetone phosphate
G3P = glyceraldehyde-3-phosphate
CELLULAR
RESPIRATION
Stage 2 & 3:
Oxidation of Pyruvate
Also called Link Reaction
Krebs Cycle
GLYCOLYSIS IS ONLY THE START
• Glycolysis
glucose      pyruvate
2x 3C
6C
• Pyruvate has more energy to yield
• 3 more C to strip off (oxidize)
• If O2 is available, pyruvate enters mitochondria
• Enzymes of Krebs cycle complete the full oxidation
of sugar to CO2
pyruvate       CO2
3C
1C
CELLULAR RESPIRATION
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
outer
intermembrane
membrane
inner
space
membrane
cristae
matrix
What cells would have
a lot of mitochondria?
mitochondrial
DNA
Oooooh!
Form fits
function!
MITOCHONDRIA - 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!
Advantage of highly folded inner
membrane?
More surface area for membranebound enzymes & permeases
MITOCHONDRIA - STRUCTURE
• Pyruvate enters mitochondrial matrix
[
2x pyruvate    acetyl CoA + CO2
3C
2C
1C
]
NAD
•
•
•
•
3 step oxidation process
Releases 2 CO2
Reduces 2 NAD  2NADH
Produces 2 acetyl-CoA
• Acetyl-CoA enters Krebs cycle
Where
does the
CO2 go?
Exhale!
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
]
KREBS CYCLE
• aka Citric Acid Cycle
• In mitochondrial matrix
• 8 step pathway
• Each catalyzed by specific enzyme
• Step-wise catabolism of 6C citrate molecule
• Evolved later than glycolysis
• Does that make evolutionary sense?
• Bacteria  3.5 bya (glycolysis)
• Free O2  2.7 bya (photosynthesis)
• Eukaryotes  1.5 bya (aerobic prokaryote 
mitochondria = organelle)
Hans Krebs
1900-1981
COUNT THE CARBONS
pyruvate
3C
2C
6C
4C
This happens
twice for each
glucose
molecule
4C
acetyl CoA
citrate
oxidation
of sugars
CO2
x2
4C
4C
6C
5C
4C
CO2
COUNT THE ELECTRON CARRIERS
pyruvate
3C
4C
acetyl CoA
6C
4C
NADH
This happens
twice for each
glucose
molecule
2C
citrate
reduction
of electron
carriers
x2
4C
FADH2
4C
ATP
6C
CO2
NADH
5C
4C
CO2
NADH
WHAT’S HAPPENED SO FAR?
• We have fully
oxidized
glucose
…C6H12O6

...…CO2
& ended up
with 4 ATP
What’s the
point?
• Krebs cycle
produces large
quantities of
electron
carriers
• NADH
• FADH2
• Go to Electron
Transport
Chain
What’s so
important about
electron carriers?
ELECTRON CARRIERS =
HYDROGEN CARRIERS
H+
H+
+
H+ H+ H
+
H + H H+
ADP
+ Pi
ATP
H+
ENERGY ACCOUNTING OF KREBS 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
VALUE OF KREBS CYCLE
• If the yield is only 2 ATP, then how was the
Krebs cycle a successful adaptation?
• The value is in 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
What’s the
point?
The point
is to make
ATP!
ATP
AND HOW DO WE DO THAT?
H+
• ATP Synthase
H+
• Set up a H+ gradient
• Allow H+ to flow
through ATP synthase
• Conformational
change bonds Pi to
ADP
ADP + Pi  ATP
But… How do we get here?
H+
H+
H+
H+
H+
H+
ADP + P
ATP
H+
We’re not done
yet!
Any questions so
far?