Metabolism

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Metabolism
Chapter 25b
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Metabolism

• The sum total of the chemical processes that
  occur in living organisms, resulting in growth,
  production of energy, elimination of waste
  material, etc.
• Anabolism- build up of complex molecules
• Catabolism- break down of complex molecules

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Fates of Organic Building Blocks in ATP Metabolism
ORGANIC BUILDING BLOCK MOLECULES Monosaccharides A
mino acids Acetates Nucleotide bases
ATP
catabolic processes
energy
energy
anabolic processes
ADPPi
Polymers other energy rich molecules
CO2 H2O
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Cellular Respiration
C6H12O6 6O2 36ADP 36Pi ? 6CO2
6H2O 36ATP
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Basic Steps Involved
1
2
3
4
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Overview of Glycolysis
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Fats
Glycogen
Protein
Other Metabolic Pathways
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Glycolysis
Glucose
C
C
C
C
C
C
2 ATP
2 ADP
2 PGAL
C
C
C
C
C
C
P
P
4 ADP
2 NAD
4 ATP
2 NADH
2 Pyruvate
C
C
C

• Net
• 2 ATP
• 2 NADH
• 2 Pyruvate molecules

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Balance Sheet for Glycolysis

• Input
• 1 Glucose
• 2 ADP Pi
• 2 NAD
• Output
• 2 Pyruvate
• 2 ATP
• 2 NADH

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Transition Reaction
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Krebs Cycle (Citric Acid Cycle)
Transition Reaction
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Krebs Cycle (Citric Acid Cycle)
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Balance Sheet for the Transition Reaction and
Krebs Cycle

• Input
• 2 Pyruvate
• 2 ADP 2 Pi
• 8 NAD
• 2 FAD

• Output
• 6 CO2
• 2 ATP
• 8 NADH
• 2 FADH2

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Krebs Cycle
Handles other substrates Intermediate molecules
used proteins and lipids Replenishment of
intermediates necessary
Hans Krebs (1937) paper originally rejected
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Krebs Cycle
Takes 2 complete cycles 8 steps, each with an
enzyme
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3
Krebs Cycle
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Oxidative Phosphorylation
Chemiosmosis
Electrons are transferred from complex to
complex and some of their energy is used to pump
protons (H) into the intermembrane space,
creating a proton gradient.
ATP synthesis is powered by the flow of H back
across the inner mitochondrial membrane through
ATP synthase.
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Each Glucose Molecule
CO2 6 NADH 10 FADH2 2 ATP 4
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Electron Transport System
CO2 6 NADH 10 FADH2 2 ATP 4
used to make ATP
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4
Electron Transport System
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Electron Transport System
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Pi
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Electron Transport Chain and Oxidative
Phosphorylation

• Electrons are delivered to O, forming O
• O attracts H to form H2O

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NADHH
Electron trans- port chain and
oxidative phosphorylation
Glycolysis
Krebs cycle
FADH2
Enzyme
Complex II
Enzyme
Complex I
Enzyme
Complex III
Free energy relative to O2 (kcal/mol)
Enzyme
Complex IV
Figure 24.9
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Electronic Energy Gradient

• Transfer of energy from NADH H and FADH2 to
  oxygen releases large amounts of energy
• This energy is released in a stepwise manner
  through the electron transport chain

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ATP Synthase

• Two major parts connected by a rod
• Rotor in the inner mitochondrial membrane
• Knob in the matrix
• Works like an ion pump in reverse

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Intermembrane space
A rotor in the membrane spins clockwise when
H flows through it down the H gradient.
A stator anchored in the membrane holds the
knob stationary.
As the rotor spins, a rod connecting the
cylindrical rotor and knob also spins.
The protruding, stationary knob contains three
catalytic sites that join inorganic phosphate
to ADP to make ATP when the rod is spinning.
ADP
Mitochondrial matrix
Figure 24.11
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Net ATP Yield
34 to 36 molecules ATP for every glucose molecule
about 40 efficiency
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Transition cycle
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Overall ATP Production
Electron Transport System 34 Citric Acid
Cycle 2 Glycolysis 2 SUBTOTAL 38 NADH Transport
into Mitochondrion -2 TOTAL 36
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Fermentation (Anaerobic Respiration)
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Lactic Acid Fermentation
NAD
NAD
NADH
NADH
C
C
C
C
C
C
C
C
C
C
C
C
(Glycolysis)
(Lactic acid fermentation)
Glucose
2 Pyruvate
2 Lactic Acid
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Glucose
Anaerobic Respiration
Aerobic Respiration
Pyruvate
no O2
O2
Acetyl CoA
Ethanol or Lactate
Krebs Cycle
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INQUIRY

• What is the end product in glycolysis?
• What substance is produced by the oxidation of
  pyruvate and feeds into the citric acid cycle?
• Name a product of fermentation.
• What role does O2 play in aerobic respiration?
• What stage during cellular respiration is the
  most ATP synthesized?
• What is chemiosmosis?
• When NAD and FAD are reduced what do they form?
• What are they used for?