Generation of ATP

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Generation of ATP

• ATP is generated (ATP synthesis) in two ways
  during respiration
• First Way Substrate-level phosphorylation
• Phosphate is removed from a substrate and added
  to ATP
• Occurs during Glycolysis and Citric Acid Cycle

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Mini Quiz Energetics

• Draw a graph illustrating the reaction rate of an
  enzyme (y) versus pH (x).
• List the major steps and locations of steps in
  cellular respiration.
• What is the purpose of cellular respiration?

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Glycolysis

• Glycolysis harvests energy by oxidizing glucose
  to pyruvate
• C-C-C-C-C-C
• Glycolysis
• Means splitting of sugar
• Breaks down glucose into pyruvate
• Occurs in the cytoplasm of the cell

C-C-C
2 Pyruvate
C-C-C
Glucose
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• Glycolysis consists of two major phases
• Energy investment phase (requires energy to get
  going)
• Energy payoff phase (generates ATP)

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1
2
Totals
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NADH an electron carrier
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Evolution and Glycolysis

• Thought to be the most primitive form of
  generating energy
• Evolved first, in an atmosphere without oxygen
• Why does it happen in the cytoplasm?
• Not very efficient!

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Glycolysis is a branching point
WITHOUT OXYGEN ANAEROBIC
WITH OXYGEN AEROBIC
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SUGARS FROM PHOTOSYNTHESIS
Glycolysis
ANAEROBIC
AEROBIC

• Fermentation
• Incomplete Oxidation
• Waste products Organic Compounds (Lactic Acid or
  Ethanol and CO2)
• Net Energy trapped 2 ATP

• Cellular Respiration
• Complete Oxidation
• Waste products H2O, CO2
• Net Energy trapped 36 ATP

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Respiration continued

• The citric acid cycle completes oxidation
  (removing electrons from glucose to make NADH)
• Takes place in the matrix of the mitochondrion
• Before the citric acid cycle can begin
• Pyruvate must first be converted to acetyl CoA,
  which links the cycle to glycolysis

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An Overview Citric Acid Cycle
Totals Requires C-C (Acetyl Co-A) Produces 2
CO2 3 NADH 3H 1 ATP 1 FADH2
2 Carbon
6 Carbon (Citric Acid)
4 Carbon
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Electron Transport and Oxidative Phosphorylation

• 2nd way for ATP synthesis (to make ATP)
• Oxidative Phosphorylation
• When ATP is generated by oxidation reactions in
  the electron transport chain.
• Energy released during each step in the electron
  transport chain is used to make ATP.
• Happens in two steps
• Electron Transport
• Chemiosmosis

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Electron Transport

• NADH and FADH2
• Carry and then Donate electrons to the electron
  transport chain
• NADH ? NAD H electron (e-)
• FADH2 ? FAD 2H 2e

RECYCLE back to glycolysis and citric acid cycle
Actively Transported into inter-membrane space
To Electron Transport
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Electron Transport
NADH (carrying electrons from food)

• Electrons are passed down a chain of proteins
  within the membrane.
• Each step in the chain is lower in energyso some
  energy is released at each step

NAD H
electrons
Energy
Energy
Energy
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Electron Transport

• At the end of the chain
• Electrons are passed to oxygen, which combines
  with 2 H to form water
• Oxygen is the final electron acceptor at the end
  of the chain

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Electron Transport

• As the electrons are passed, each step down
  releases energy.
• The energy lost at each step in the chain is used
  to pump H from the mitochondrial matrix to the
  intermembrane space.
• Why does this require energy?

H
INTER-MEMBRANE
MATRIX
H
H
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Chemiosmosis

• H ions become concentrated in the inter-membrane
  space and want to move down their concentration
  gradient.
• The only site on the membrane that allows H back
  through is the protein called ATP synthase

H
H
H
H
H
MATRIX
INTER-MEMBRANE SPACE
H
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• ATP synthase uses the energy stored in the
  hydrogen ion gradient to make ATP
• This is called chemiosmosis using a hydrogen ion
  gradient to drive cellular work.

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ATP is made through

• Oxidative Phosphorylation the combination of the
  electron transport chain and chemiosmosis.
• Total makes 32-34 ATP!! Thats good!