Glycolysis

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Cell
Energetics 2

• Glycolysis

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Overview of metabolism

• Usable energy is released as reactions break down
  carbon compounds, such as glucose.
• The released energy is used to drive an electron
  transport chain which drives ATP production.
• Cells use ATP to meet their energy needs.

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Complete Glucose Metabolism

• The overall equation for glucose metabolism can
  be written as
• C6H12O6 6 O2 6CO2 6 H2O

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Glycolysis

• Literally, glycolysis means sweet breaking. In
  glycolysis, glucose is split into two 3-carbon
  chains.
• The process of glycolysis requires 2 ATP
  molecules and produces 4, for a net gain of 2
  ATPs from each molecule of glucose.
• Glycolysis does not require oxygen.

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Glucose Metabolism Overview
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Glycolysis overview
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Glycolysis Energy Investment

• Glycolysis takes place in the cytoplasm.
• First step is energy investment ATP is used to
  split glucose and make 2 3-carbon molecules. Each
  molecule is phosphorylated (phosphorus added).

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Glycolysis Energy Payoff

• Next is the energy payoff phase.
• The 3-carbon molecule gives up phosphorus, which
  is used to make 4 ATPs. NADH, an electron
  carrier, is also produced.
• The result are 2 3-carbon chains called pyruvate.

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Without oxygen...

• In anaerobic conditions, hydrogen ions and
  electrons freed in glycolysis can accumulate.
• NAD accepts free electrons and hydrogen ions to
  become NADH as usual, but NADH then accumulates.
  This could bring glycolysis to a halt.

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Anaerobic fermentation

• Fermentation deals with accumulated NADH.
• Pyruvate becomes the final electron and hydrogen
  ion acceptor. Pyruvate is converted into either
  lactate (lactic acid) or ethanol, depending on
  the organism.

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Anaerobic Fermentation
In the absence of oxygen, yeast can make some ATP
from glucose. Alcohol is the waste product.
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Anaerobic Fermentation
During hard exercise, muscles may be deprived of
oxygen. The muscles extract some energy from
glucose, and produce lactic acid, which is later
broken down when oxygen is available.
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Summary

• Glycolysis is the process of splitting 6-carbon
  glucose into two 3-carbon chains (pyruvate).
• Two ATP molecules are generated.
• However, there is still a lot of potential energy
  in the bonds in pyruvate.
• Next Into the mitochondria.