Chapter 5 (Cellular Respiration)

8/13/2019 Chapter 5 (Cellular Respiration)

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Cell Respiration

Chapter 5

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Outline

Chemical Energy DrivesMetabolismGlucose Catabolism

GlycolysisPyruvate OxidationKrebs Cycle

Electron Transport Chain Aerobic Respiration SummaryEnergy Storage

Fermentation


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Using Chemical Energy toDrive Metabolism

Autotrophs - Convert radiantenergy into chemical energy.Heterotrophs - Live on energyheterotrophs produce.

Digestion - Breaking down largemolecules with enzymes.Catabolism - Harvesting energyfrom C-H.


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Using Chemical Energy toDrive Metabolism

Aerobic Respiration - Oxygen gasaccepts the hydrogen atom andwater forms.

Anaerobic Respiration - Occurswhen an inorganic molecule otherthan oxygen accepts the hydrogen.Fermentation - Occurs when anorganic molecule accepts thehydrogen atom.C6H12 O 6 + 6 O 2 6 CO 2 + 6 H 20 +

energy


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ATP

Adenosine triphosphate (energycurrency)

Composed of:Five-carbon sugar (ribose)

AdenineTriphosphate group

Energy StoragePhosphate groups are highlynegatively charged.

Unstable bonds easily broken.


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ATP

Cells use ATP to driveendergonic reactions.

Instability makes ATP ideal forshort-term energy source, but apoor candidate for long-termenergy storage.


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ATP

ATP serves as cells energycurrency.

LocomotionEndergonic Reactions

Enzyme driving reaction has twobinding sites. One for the reactantand one for ATP.

Energy released from ATP pushes thereactant at the site up the gradient.


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Overview of GlucoseCatabolism

Cells catabolize organicmolecules and make ATP twoways:

Substrate-Level PhosphorylationGlycolysis

Aerobic Respiration

Pyruvate OxidationKrebs CycleElectron Transport Chain


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Aerobic Respiration Overview

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GlycolysisBiochemical pathway thatproduces ATP by substrate-levelphosphorylation.

Yields a net of two ATP molecules foreach molecule of glucosecatabolized.


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Anaerobic RespirationIn the absence of oxygen, someorganisms can still respireanaerobically, using inorganicmolecules to accept electrons.

MethanogensSulfur Bacteria


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Glycolysis

PrimingGlucose PrimingCleavage and Rearrangement

Substrate-Level PhosphorylationOxidation

ATP Generation


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Glycolysis

All Cells Use GlycolysisEvery living creature is capable ofcarrying out glycolysis.

Most present-day organisms canextract considerably more energyfrom glucose through aerobicrespiration.


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Glycolysis

Two molecules of NAD + arereduced to NADH. Thus NAD + must be regenerated forglycolysis to continue unabated.

Aerobic RespirationFermentation


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Oxidation of Pyruvate

In stage two of glucosecatabolism, pryuvate isdecarboxylated, yielding:

acetylCoANADHCO 2.

Occurs within mitochondrian.


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Krebs Cycle

The Krebs Cycle generates two ATP molecules per molecule ofglucose.

Harvest many energized electronswhich can be directed to theelectron transport chain to drive

synthesis of more ATP.
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Krebs Cycle

OverviewStep A: PrimingStep B: Energy Extraction

ReactionsReaction 1 - CondensationReactions 2 and 3 -IsomerizationReaction 4 - First OxidationReaction 5 - Second

Oxidation
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Krebs CycleReaction 6 - Substrate-Level PhosphorylationReaction 7 - Third OxidationReactions 8 and 9-Oxaloacetate Regeneration


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Electron Extraction

Catabolism of glucose involvesa series of oxidation-reductionreactions that release energy byre-depositing electrons closer tooxygen atoms.Energy is thus harvested fromglucose in gradual steps, usingNAD+ as an electron carrier.


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Electron Transport Chain

The electrons harvested fromglucose are pumped out of themitochondrial matrix by theelectron transport chain.

Return of protons onto the matrixgenerates ATP.


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Summarizing AerobicRespiration

Oxidative reduction producesapproximately 30 molecules of

ATP from each molecule ofglucose in eukaryotic cells.

About one-third of the energy inthe chemical bonds of glucose.


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Regulating AerobicRespiration

Relative levels of ADP and ATPregulate the catabolism ofglucose at key committingreactions.


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Energy Storage

Proteins, fats, and other organicmolecules are also metabolizedfor energy.

Amino acids of proteins are firstdeaminated while fats undergo -oxidation.


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Fermentation

Fermentation occurs in theabsence of oxygen.

Electrons that result from theglycolytic breakdown of glucoseare donated to an organicmolecule regenerating NAD + fromNADH.


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Review

Chemical Energy DrivesMetabolismGlucose Catabolism

GlycolysisPyruvate OxidationKrebs CycleElectron Transport Chain

Aerobic Respiration SummaryEnergy Storage


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Chapter 5 (Cellular Respiration)