Biochemistry Bioenergetics: How the body converts food to energy

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BiochemistryBioenergeticsHow the body
convertsfood to energy
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Bioenergetics

• Metabolism The sum of all Chemical Reactions
  involved in maintaining the dynamic state of the
  cell
• Catabolism - breaking down of molecules to supply
  energy
• Anabolism - synthesis of molecules
• Biochemical Pathway - a series of consecutive
  chemical reactions

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Common Catabolic Pathway

• Conversion of FOOD to ATP
• FOOD produces C4 and C2 fragments
• C4 and C2 fragments enter Citric Acid Cycle
• CO2, NADH, FADH2, are produced
• Electron Transport produces ATP

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Cells and Mitochondria

• Components of a typical cell
• nucleus - replication of cell begins here
• lysosomes - remove damaged cellular components
• Golgi bodies - package and transport proteins
• organelles - specialized structures with specific
  function
• mitochondria - common catabolic pathway

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Cells and Mitochondria
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Cells and Mitochondria
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Mitochondria

• Mitochondria
• Two membranes
• Common Catabolic Pathway
• Enzymes located in folds or Crista
• Transport thru the inner membrane occurs with the
  help of Protein Gates

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Mitochondrion
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Common Catabolic Pathway

• 2 Parts
• Citric Acid Cycle
• or Tricarboxylic Acid Cycle
• or TCA cycle
• or Krebs Cycle
• Oxidative Phosphorylation
• or Electron Transport
• or Respiratory Chain

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Compounds - ADP

• Adenosine diphosphate (ADP)

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Compounds - ATP

• AMP, ADP, ATP

High energy phosphate anhydride bonds
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Compounds - ATP

• ATP
• We make about 88 lbs. of ATP a day!!!
• Used for
• muscle contraction
• nerve signal conduction
• biosynthesis

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Fig. 26.6, p.651
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Compounds - Redox

• NAD and FAD
• Oxidizing agents
• Actually coenzymes
• Contain an ADP core (part of R or R)

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Compounds - Redox

• NAD is converted to NADH

Oxidized form
Reduced form
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Compounds - Redox

• FAD is converted to FADH2

Oxidized form
Reduced form
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Compounds

• The Acetyl carrying group - Acetyl coenzyme A
• Carrying handle is Pantothenic Acid and
  Mercaptoethylamine

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Coenzyme A

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Coenzyme A

4C
3C
2C
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Fig. 26.8, p.652
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Citric Acid Cycle

• Acetyl CoA contains a 2 carbon fragment that is
  carried into the Citric Acid Cycle
• Also called the
• Tricarboxylic Acid Cycle
• TCA Cycle
• Krebs Cycle
• Acetyl group is split out as CO2

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Citric Acid Cycle

• Step 1
• oxaloacetate will show up in last step
• acetyl CoA is the THIO ESTER of acetic acid (CoA
  is Co Enzyme A)

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Citric Acid Cycle

• Step 1B
• citrate or citric acid produced
• citrate has 6 C (How many acid groups?)

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Fig. 26.8, p.652
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Citric Acid Cycle

• Step 2
• dehydration to cis-Aconitate
• hydration to isocitrate
• enzymes required for each Rx

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Fig. 26.8, p.652
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Citric Acid Cycle

• Step 3
• oxidation and decarboxylation
• CO2 is from the ???

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Fig. 26.8, p.652
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Citric Acid Cycle

• Step 4
• Where did the CO2 come from???

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Fig. 26.8, p.652
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Citric Acid Cycle

• Step 5
• GTP is Guanosine triphosphate (as good as ATP!)

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Fig. 26.8, p.652
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Citric Acid Cycle

• Step 6
• Oxidation with FAD
• Fumaric Acid is trans-Fumaric Acid
• Barbiturate is an inhibitor of Succinate
  dehydrogenase

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Fig. 26.8, p.652
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Citric Acid Cycle

• Step 7
• hydration reaction
• fumarase is enzyme

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Citric Acid Cycle

• Step 8
• oxidation using NAD
• product is oxaloacetate!

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Fig. 26.8, p.652
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Electron (and H) Transport

• End products of the Citric Acid Cycle
• Reduced (or spent) Coenzymes
• NADH
• FADH2
• Carry H and e- and yield energy when combining
  with oxygen

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Electron (and H) Transport

• Many Enzymes are involved in ET
• Enzymes are imbedded in inner membrane of the
  mitochondria
• Enzymes are in a particular sequence
• each accepts electrons
• increasing affinity for electrons
• Final acceptor of electrons is molecular O2 to
  make water

O2
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Fig. 26.10, p.656
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Electron Transport chain - youtube
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Electron (and H) Transport

• Many Enzymes are involved in Oxidative
  Phosphorylation

O2-
ATP
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The Energy Yield from a C2

• Each NADH produces 3 ATP
• Each FADH2 produces 2 ATP
• (Each pair of H produces 1 ATP)
• For each C2 unit (acetyl CoA) we produce...
• 1 GTP directly (same as 1 ATP) from step 5 TCA
• 3 NADH in ET (3 x 3 9 ATP) Indirect
• 1 FADH2 in ET (1 x 2 2 ATP) Indirect
• For a total of ..................... 12 ATP
• (and some waste CO2)

Indirect (from ET)

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Conversion of ATP

• How does the body utilize this Chemical Energy?
• Conversion to Other Forms
• biosynthesis
• Electrical Energy
• ion gradients (K, Na)
• Mechanical Energy
• muscle contraction
• Heat Energy
• maintain 37 oC or 98.6 oF

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Muscle Contraction

• Chemical Energy converted to Mechanical Energy
• Thick (myosin) and thin (actin) filaments
• Hydrolysis of ATP causes the interaction of the
  filaments (muscle contraction)