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Lecture 16

BIOL 3113 Lecture Notes - Lecture 16: Citric Acid Cycle, Oxidative Phosphorylation, Partial Oxidation

Course Code
BIOL 3113
Barbara S

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15, 16 Energy Generation
Cells require a constant supply of energy
Two basic reactions responsible for life:
6CO2 + 6H2O C6H12O6 + 6O2
Uses energy from sunlight to reduce carbon from atmospheric CO2 to sugar
O2 produced as a by-product
*Oxidative Catabolism
C6H12O6 + 6O2 6CO2 + 6H2O
Oxidizes carbon from sugar to release energy to power metabolism
CO2 produced as a by-product
ATP - main source of energy for many reactions in cells
In eucaryotes ATP produced:
*during glycolysis (small amount)
*in mitochondria (most of ATP production)
*in chloroplasts (plants and green algae)
The process of ATP production - chemiosmotic coupling
In mitochondria and chloroplasts, in cell membrane of many bacteria
Breakdown of Food
Enzymatic hydrolysis of macromolecules
digestive tract/organelles
partial oxidation of glucose to pyruvate
in the cytosol
does not require oxygen
basis of anaerobic metabolism
*Citric Acid Cycle
in matrix of mitochondria
requires oxygen
*Oxidative Phosphorylation
driven by electron transport across the inner mitochondrial membrane
generates ATP wrequires oxygen

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Partial oxidation of glucose (6 carbon) to pyruvate (3 carbon)
*Does not require oxygen
*Occurs in steps - allow energy to be efficiently captured
*Production of ATP and NADH
Net result of glycolysis
2 molecules of pyruvate
2 molecules of ATP
2 molecules of NADH
Oxidation of Pyruvate
In mitochondrial matrix
Pyruvate acetyl CoA + CO2
Sources of pyruvate:
Ÿamino acids
A, B, C pyruvate dehydrogenase complex
Net result:
Citric Acid Cycle
In mitochondrial matrix
Oxidation of acetyl CoA to CO2
Fatty acids also oxidized to acetyl CoA
Net result:
Glycolysis and Citric Acid Cycle- generation of precursors for biosynthesis
*amino acids
produced during glycolysis and citric acid cycle are used as the precursors for synthesis of many

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Double membrane organelle of variable size and shape that provides a site for:
*Oxidation of pyruvate acetyl CoA + NADH
*Oxidation of fatty acids acetyl CoA + NADH + FADH2
*Citric acid cycle NADH + FADH2+ GTP
*Oxidative phosphorylation
Main site of energy production in eucaryotic cells
Very efficient:
*glycolysis harvests less than 10% of the total free energy potentially available from the glucose (2 ATP
molecules produced per glucose molecule)
*in mitochondria - ~30 ATP molecules produced for each glucose molecule
their own DNA and RNA
complete transcription and translation machinery (ribosomes)
*present in large numbers (~2000 in hepatocytes)
*can be extremely motile or stationary
*stay in close location to a site of high ATP consumption (close to the contractile apparatus in muscle cells,
wrapped tightly around the base of the motile flagellum)
*defects in mitochondrial function - serious effects on the body function (especially affected are tissues with
high energy need e.g. muscles and nervous tissue; MERRF - myoclonic epilepsy and ragged red fiber disease -
mutation in one of mitochondrial tRNA genes decrease in synthesis of electron transport proteins)
Mitochondria are double membrane organelles with a single internal compartment:
Outer Membrane
many transmembrane channels produced by porin - permeable
to molecules < 5000 daltons
enzymes involved in mitochondrial lipid synthesis
enzymes converting lipids into forms metabolized in
mitochondrial matrix
Intermembrane Space
*contains enzymes that use ATP passing out of
the matrix to phosphorylate other nucleotides
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