Bot 130 Lecture 11

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• Respiration
• Bot 130 Lecture 11

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Respiration
Glycolysis
Krebs cycle
Carbon dioxide
Glucose
Pyruvate
Some energy
More energy
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Respiration (the redox part)
Glycolysis
Krebs cycle
Carbon dioxide
Glucose
Pyruvate
Some electrons
More electrons
Oxidative electron transport
Oxygen
Boatloads of ATP
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Respiration (where)
Mitochondrion
Cytosol
Carbon dioxide
Glucose
Pyruvate
Some electrons
More electrons
Oxidative electron transport
Oxygen
Boatloads of ATP
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Respiration begins with glycolysis

• Glycolysis is defined to be the conversion of
  glucose to pyruvate but we can talk about short
  sections of glycolysis as glycolytic reactions

Glucose ? A ? B ? C ? D ? E ? pyruvate
Glycolysis
B ? C ? D Glycolytic
reactions
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Respiration begins with glycolysis

• Glycolysis begins with the investment of energy

P
P
O
O
O
ATP ?
?
Glucose
Glucose 6P
Fructose 6P
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Respiration begins with glycolysis

• And now, even more investment

P
P
P
O
O
ATP ?
Fructose 6P
Fructose 1,6-bisP
This is a very highly regulated step.
Phosphofructokinase
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Glycolysis

• The next step is breaking apart the F1,6BP

P
P
?
?
P
O
O
Dihydroxyacetone P and Glyceraldehyde 3P
Fructose 1,6-bisP
Triose phosphates
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Glycolysis

• The triose phosphates can be interconverted
• DHAP is the favored configuration (isomer)
• BUT, the aldehyde version is the one that
  continues

P NAD NADH
CO C C-P
C CO C-P
P CO C C-P
?
Triose phosphate isomerase
1,3 bisphosphoglycerate
GAP dehydrogenase
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Glycolysis

• The GAP dehydrogenase step is very important
• Harvest of two electrons
• Reducing power must be dealt with (later)
• Happens twice for each glucose molecule (2X2 4
  electrons per glucose)

P NAD NADH
CO C C-P
P CO C C-P
GAP dehydrogenase
1,3 bisphosphoglycerate
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Glycolysis

• The next step recovers ATP
• It is named for the reverse reaction (a common
  thing in biochemistry, and the reaction is
  perfectly reversible, as we shall see in
  photosynthesis)

PGA kinase
O- CO C C-P
P CO C C-P
ADP ATP
1,3 bisphosphoglycerate
3-phosphoglyceric acid
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Glycolysis

• Up to this point, 2 ATP used, two ATP produced
• Reducing power, electrons, have been transferred
  from the sugar to NAD

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Glycolysis (continued)

• In the second half of glycolysis the
  phosphorylated acid is rearranged and the
  phosphate is used to make another ATP
• An inportant intermediate is phosphenolpyruvate,
  known to one and all as PEP.

ADP ATP
3 phosphoglycerate ? ? PEP pyruvic
acid (pyruvate)
True or false the last enzyme in glycolysis is
called pyruvate kinase True the backwards
reaction is a kinase reaction False reactions
always proceed in the direction of losing energy
(exergonic)
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Important compounds in glycolysis

• Four C-O bonds in glyceraldehyde 3-P
• Same redox state as glucose
• Oxidation plus ATP synthesis

• Five C-O bonds in 3-phosphoglycerate and pyruvate
• The phosphate can be harvested to make ATP
• No redox in this step

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Glycolysis (summary)

• 2 ATP used to start, 4 ATP made, net 2 ATP
• 2 NADH molecules made
• Glucose converted to pyruvate
• All reactions occur in the cytosol

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Now what?
Pyruvate
No oxygen - fermentation, cytosolic
With oxygen - respiration, mitochondrial
Pyruvate
Lactate
Off to the mitochondrion!
NADH NAD
Pyruvate
Ethanol CO2
Net Glucose becomes two molecules of ethanol
plus 2 CO2 plus 2 ATP. 80 of the energy in the
glucose is still trapped in the ethanol.
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What does the mitochondrion do?

• Two things
• Metabolize pyruvate to CO2 in the Krebs Cycle
• Use the reducing power of NADH to make ATP

CO2
Step 1
acetyl coenzyme A
Pyruvate
Coenzyme A
This reaction and the Krebs Cycle occur in the
matrix of the mitochondria.
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The first thing that happens in the mitochondrion
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What does the mitochondrion do?

• Step 2 The Krebs Cycle

acetyl coenzyme A
Citrate
CO2 NADH
Oxaloacetate
?-ketoglutarate
NADH
CO2 NADH ATP (GTP)
Malate
Succinate
Fumarate
FADH2
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What does the mitochondrion do?

• Step 2 The Krebs Cycle

acetyl coenzyme A
Citrate
CO2 NADH
Oxaloacetate
?-ketoglutarate
NADH
CO2 NADH ATP (GTP)
Malate
Succinate
Fumarate
FADH2
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What does the mitochondrion do?

• Step 2 The Krebs Cycle

acetyl coenzyme A
Citrate
CO2 NADH
Oxaloacetate
?-ketoglutarate
NADH
CO2 NADH ATP (GTP)
Malate
Succinate
Fumarate
FADH2
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What do mitochondria do?

• After steps 1 and 2, pyruvate is completely
  broken down to CO2 and a lot of NADH has been
  made
• No oxygen has been used yet.
• In Step 3 (the final step) the energy locked up
  in the reducing power is unlocked to make large
  amounts of ATP.
• The reactions that convert NADH to ATP occur on
  the inner mitochondrial membrane (the cristae).

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Respiration (where)
Mitochondrion
Cytosol
Carbon dioxide
Glucose
Pyruvate
Some electrons
More electrons
Oxidative electron transport
Oxygen
Boatloads of ATP