Cellular Respiration

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Cellular Respiration

• Honors Biology

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What is Cellular Respiration?

• The process of converting food energy into ATP
  energy
• C6H12O6 6 O2 ? 6 CO2 6 H2O 36 ATP

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Why are both Photosynthesis and Cell Respiration
important to Ecosystems?

• Light is the ultimate source of energy for all
  ecosystems
• Chemicals cycle and Energy flows
• Photosynthesis and cellular respiration are
  complimentary reactions

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Why do plants need both chloroplasts and
mitochondria?

• Chloroplasts use energy from the sun to make
  glucose
• Mitochondria convert glucose to ATPthe energy
  currency of the cell

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What is ATP?

• Adenosine Triphosphate
• 5-Carbon sugar (Ribose)
• Nitrogenous base (Adenine)
• 3 Phosphate groups
• Energy currency of the cell
• The chemical bonds that link the phosphate groups
  together are high energy bonds
• When a phosphate group is removed to form ADP and
  P, small packets of energy are released

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How is ATP used?

• As ATP is broken down, it gives off usable energy
  to power chemical work and gives off some
  nonusable energy as heat.
• Synthesizing molecules for growth and
  reproduction
• Transport work active transport, endocytosis,
  and exocytosis
• Mechanical work muscle contraction, cilia and
  flagella movement, organelle movement

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Why use ATP energy and not energy from glucose?

• Breaking down glucose yields too much energy for
  cellular reactions and most of the energy would
  be wasted as heat.
• 1 Glucose 686 kcal
• 1 ATP 7.3 kcal
• 1 Glucose ? 36 ATP
• How efficient are cells at converting glucose
  into ATP?
• 38 of the energy from glucose yields ATP,
  therefore 62 wasted as heat.

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Cellular Respiration is a Redox Reaction

• C6H12O6 6 O2 ? 6 CO2 6 H2O
• Oxidation is the loss of electrons or H
• Reduction is the gain of electrons or H
• Glucose is oxidized when electrons and H are
  passed to coenzymes NAD and FAD before reducing
  or passing them to oxygen.
• Glucose is oxidized by a series of smaller steps
  so that smaller packets of energy are released to
  make ATP, rather than one large explosion of
  energy.

(Reduction)
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Cell Respiration can be divided into 4 Parts

• 1) Glycolysis
• 2) Oxidation of Pyruvate / Transition Reaction
• 3) The Krebs Cycle
• 4) The Electron Transport Chain and
• Chemiosmotic Phosphorylation

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Where do the 4 parts of Cellular Respiration take
place?

• Glycolysis
• Cytosol
• Oxidation of Pyruvate
• Matrix
• The Krebs Cycled
• Matrix
• Electron Transport Chain and Cheimiosmotic
  Phosphorylation
• Cristae

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Parts of the Mitochondria
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Anaerobic Respiration (no oxygen required,
cytoplasm)

• Glycolysis
• (substrate level)

Glucose ? 4 ATP (Net 2 ATP) 2 ATP 2 NADH 2
Pyruvate
Aerobic Respiration (oxygen required,
mitochondria)
2. Oxidation of Pyruvate
2 Pyruvate ? 2 CO2 2 NADH 2 Acetyl CoA

• Krebs Cycle
• (substrate level)

2 Acetyl CoA ? 4 CO2 2 ATP 6 NADH 2 FADH2

• Electron
• Transport
• Chain
• (chemiosmotic)

10 NADH ? 32 ATP 2 FADH2 6 H2O 6 O2
Total 36 ATP produced
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ATP is made in two ways

• 1) Substrate Level Phosphorylation (glycolysis
  Krebs cycle)
• 2) Chemiosmotic Phosphorylation (electron
  transport chain)
• Substrate-Level Phosphorylation
• Energy and phosphate are transferred to ADP using
  an enzyme, to form ATP. Phosphate comes from one
  of the intermediate molecules produced from the
  breakdown of glucose.

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Glycolysis
Glucose ? 2 Pyruvate 2 ATP 4 ATP (Net 2
ATP) 2 NADH

• Glucose (C6) is split to make
• 2 Pyruvates (C3)
• 1st ATP energy used to phosphorylate glucose
  (stored energy)
• 2nd phosphorylated glucose broken down into two
  C3 sugar phosphates
• 3rd the sugar phosphates are oxidized to yield
  electrons and H ions which are donated to 2 NAD
  ? 2 NADH (stored electron and hydrogen for the
  Electron Transport Chain)
• 4th The energy from oxidation is used to make 4
  ATP molecules (net 2 ATP)
• This is substrate level phosphorylation because
  an enzyme transfers phosphate to ADP making ATP
• Glycolysis produces very little ATP energy, most
  energy is still stored in Pyruvate molecules.

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Oxidation of Pyruvate /Transition Reaction
2 Pyruvate ? 2 CO2 2 NADH 2 Acetyl CoA

• When Oxygen is present, 2 Pyruvates go to the
  matrix where they are converted into 2 Acetyl CoA
  (C2).
• Multienzyme complex
• 1st each Pyruvate releases CO2 to form Acetate.
• 2nd Acetate is oxidized and gives electrons and
  H ions to 2 NAD ? 2 NADH.
• 3rd Acetate is combined with Coenzyme A to
  produce 2 Acetyl CoA molecules.
• 2 NADHs carry electrons and hydrogens to the
  Electron Transport Chain.

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The Krebs Cycle / Citric Acid Cycle
2 Acetyl CoA ? 4 CO2 2 ATP 6 NADH 2 FADH2

• 8 Enzymatic Steps in Matrix of Mitochondria
  Break down and Oxidize each Acetyl CoA (2-Cs) to
  release 2 CO2 and yield electrons and H ions to
  3 NAD 1 FAD ? 3 NADH FADH2. This
  yields energy to produce ATP by substrate level
  phosphorylation.
• The first step of the Krebs cycle combines
  Oxaloacetate (4 Cs) with Acetyl CoA to form
  Citric Acid, then the remaining 7 steps
  ultimately recycle oxalacetate.
• Two Turns of the Krebs Cycle are required to
  break down both Acetyl Coenzyme A molecules.
• The Krebs cycle produces some chemical energy in
  the form of ATP but most of the chemical energy
  is in the form of NADH and FADH2 which then go on
  to the Electron Transport Chain.

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The Electron Transport Chain
10 NADH ? 32 ATP 2 FADH2 H2O Oxygen

• NADH and FADH2 produced earlier, go to the
  Electron Transport Chain.
• NADH and FADH2 release electrons to
  carriers/proteins embedded in the membrane of the
  cristae. As the electrons are transferred, H
  ions are pumped from the matrix to the
  intermembrane space up the concentration
  gradient. Electrons are passed along a series of
  9 carriers until they are ultimately donated to
  an Oxygen molecule.
• ½ O2 2 electrons 2 H (from NADH and FADH2) ?
  H2O.

http//vcell.ndsu.nodak.edu/animations/etc/movie.h
tm
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Chemiosmotic Phosphorylation

• Hydrogen ions travel down their concentration
  gradient through a channel protein coupled with
  an enzyme called ATP Synthase.
• As H ions move into the matrix, energy is
  released and used to combine ADP P ? ATP.
• Hydrogens are recycled and pumped back across the
  cristae using the Electron Transport Chain.
• ATP diffuses out of the mitochondria through
  channel proteins to be used by the cell.

http//vcell.ndsu.nodak.edu/animations/atpgradient
/movie.htm
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ATP Synthase

• Multisubunit complex with 4 parts
• Rotor spins as H ions flow
• Stator holds the rotor and knob complex
  together in the cristae
• Internal Rod extends between rotor and knob,
  spins when rotor spins which then turns the knob
• Knob contains 3 catalytic sites that when
  turned change shape and activate the enzyme used
  to make ATP

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Review ATP Production

• 1) Glycolysis ? 2 ATP
• 2) Oxidation of Pyruvate ? No ATP
• 3) The Krebs Cycle ? 2 ATP
• 4) The Electron Transport Chain and Chemiosmotic
  Phosphorylation
• Each NADH produces 2-3 ATP so 10 NADH ? 28 ATP
• Each FADH2 produces 2 ATP so 2 FADH2 ? 4
  ATP
• Total 36 ATP
• 1 Glucose 686 kcal
• 1 ATP 7.3 kcal
• 1 Glucose ? 36 ATP
• How efficient are cells at converting glucose
  into ATP?
• 38 of the energy from glucose yields ATP,
  therefore 62 wasted as heat (used to maintain
  body temperature or is dissipated)
• Ex. Most efficient Cars only 25 of the energy
  from gasoline is used to move the car, 75 heat.

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All Types of Molecules can be used to form ATP
by Cell Respiration

• Proteins, Carbohydrates, and Lipids must first be
  broken down into their monomers and absorbed in
  the small intestine.
• Monomers may be further broken down into
  intermediate molecules before entering different
  parts of Cell respiration to ultimately form ATP.

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Anaerobic Respiration Fermentation

• If there is NO oxygen, then cells can make ATP by
  Fermentation
• Without oxygen, Oxidation of Pyruvate and the
  Electron Transport Chain do not operate.
• Glucose ? Pyruvate ? Lactate
• NAD Glycolysis 2 NADH Reduction Rxn
  or
• 2 ATP Alcohol CO2
  
• Fermentation yields a net gain of 2 ATP by
  substrate level phosphorylation for every 1
  Glucose. (Inefficient)
• Two Forms of Fermentation
• Lactic Acid Fermentation (animals)
• Alcohol Fermentation (yeast)