How Do Organisms Supply Themselves With Energy?

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Chapter 6
How Do Organisms Supply Themselves With Energy?
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Key Questions

• How do organisms supply themselves with energy?
• How do organisms extract energy from glucose?
• How is the energy in glucose used to make ATP?

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How Do Organisms Supply Themselves With Energy?

• All organisms need energy
• Ultimate source of energy on the Earth is the sun
• Autotrophs make their own food
• examples plants, some bacteria
• Heterotrophs obtain chemical energy from other
  organisms
• Examples?

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Energy Currency

• Adenosine Triphosphate or ATP
• Cellular respiration produces ATP
• Aerobic versus anaerobic

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Cellular Respiration
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Steps of Cellular Respiration

• Step 1 glycolysis
• Step 2 acetyl-CoA formation
• Step 3 citric acid cycle
• Step 4 electron transport and oxidative
  phosphorylation
• Overall equation glucose oxygen carbon
  dioxide water ATP

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Cellular Respiration Chemical Formula

• C6H12O6 6O2
• Glucose Oxygen
• 6CO2 6H2O ATP
• Carbon Water Energy
• Dioxide

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What Is Oxidation?

• Oxidizing agent or electron acceptor accepts an
  electron
• Reducing agent or electron donor donates an
  electron
• Oxidation and reduction always go hand in hand
• Examples of acceptors O2, NAD, FAD

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Step 1 GlycolysisOccurs in Cytoplasm

• Part 1 6 carbons are split into 3-carbon
  molecules and are phosphorylated uses ATP
• Part 2 Phosphates and electrons are removed
  electrons added to NAD to make NADH produces 2
  ATP

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Step 1 Glycolysis Cont.

• Part 3
• More electrons and phosphates are removed from
  the 3-carbon molecules
• phosphates are added to ADP to make ATP

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Glycolysis Overview

• Breaks glucose into 2 molecules of pyruvate,
  generating 2 molecules of ATP and 2 molecules of
  NADH
• Aerobic or anaerobic?
• The pyruvate enters a cells _______.
• When compounds are reduced, they ___ electrons.
• When compounds are oxidized, they ___ electrons.
• Which molecules/coenzymes from Glycolysis accept
  electrons?

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Step 2 Acetyl CoAOccurs in ______

• Oxygen needed for this reaction aerobic
• Pyruvate loses a carbon and 2 oxygens in the form
  of CO2
• Enzymes link coenzyme A to the acetate
• CoA synthesizes fatty acids.

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Step 3 Citric Acid CycleOverview

• High energy electrons are captured in the form of
  NADH and FAD
• Occurs in the matrix of the mitochondria
• With each turn of the cycle, citrate loses a
  total of 8 electrons to electron acceptors such
  as NAD

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Step 3 Citric Acid Cycle

• 3 parts
• Part 1 6-carbon citrate and isocitrate formation
• Part 2 conversion of isocitrate into a 4-carbon
  compound
• Part 3 production of another molecule of OAA,
  which starts the cycle over again

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Citric Acid Cycle
The acetyl group is oxidized and energy is
captured as ___, ___, ____.
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What If There Is No Oxygen?

• After glycolysis, if there is no oxygen,
  fermentation will occur
• Cells must regenerate more NAD from NADH
• Yeast form ethanol (terminal reaction produces
  CO2 )
• Animals form lactic acid (ouch)

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Biochemical Pathway Intersections
Figure 6-7

• Catabolism breakdown of complex molecules such
  as food produces energy, involves oxidation
• Anabolism synthesis of complex molecules uses
  energy

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How Do Other Food Molecules Enter Metabolism?

• Fat, carbohydrates and proteins enter the
  cellular respiration pathway at different points

• The most likely point is at acetyl CoA

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Electron Transport Chain
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Step 4 Electron Transport Oxidative
Phosphorylation

• The pathway of electrons from one carrier to
  another is called ____ ____ _____
• Each electron carrier passes its electrons to the
  next carrier (bucket brigade)
• Most of the electrons to the electron transport
  chain are received from what cycle?
• A reduced carrier becomes oxidized when it gives
  up its electrons (forms ATP from ADP)
• Oxygen accepts electrons

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How Do Cells Harvest Energy?

• Proton gradient flow of electrons through the
  electron transport chain creates this gradient
  (ATP is made from this gradient)
• Chemiosmosis harnessing of the energy stored in
  the chemical gradient some machinery in the
  membrane must do this process

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Generating a Proton Gradient

• Mitochondria inner and outer membrane
• Intermembrane space space between 2 membranes
• Matrix space w/n the inner membrane makes up
  about 2/3 of the volume ETC is embedded in this
  inner membrane

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Pumping Protons

• pH cytochromes assist w/ transport of
  electrons.
• Gradient is produced when..

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ATP Synthase

• Proton complex
• Protons flow through these channels back into the
  matrix
• Works like a turbine
• Uses energy to make ATP

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Fragments of Inner Membrane
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Think About This One!

• Why might you lose weight (a lot of weight) if
  your mitochondria suddenly lost the ability to
  couple electron transport to the production of
  ATP?

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Key Concepts

• Cellular respiration converts the chemical energy
  of food molecules into the chemical energy of ATP
• Most cells can use glycolysis to obtain energy
• ATP production from cellular respiration depends
  on oxidative phosphorylation