Bioenergetics

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Bioenergetics Chapter 5 Lecture 2
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Lecture 2

• More on enzymes
• Redox Reactions
• Introduction to Respiration

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Enzymes are very specific
Each enzyme generally only works with one set of
substrates Enzymes have a particular set of
environmental conditions at which they work best
(i.e. temperature, pH, salt concentration)
Example 1 Most human enzymes work best at 35 to
40 C. Enzymes of bacteria found in hot springs
work best at 60 to 70 C Example 2 Most human
enzymes work best at pH between 6 to 7. The
digestive enzyme pepsin which is found in the
very acidic environment of the stomach works best
at a pH of 2.
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Enzymes can be inhibited in a variety of ways
Many pesticides and antibiotics work by
inhibiting certain essential enzymes in the
target species
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Allosteric Regulation
Allosteric site specific receptor site on some
part of the enzyme molecule other than the active
site.
Active conformation Inactive
Conformation
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Introduction to Redox Reactions
Oxidation-Reduction reactions chemical
reactions that involve the partial or complete
transfer of electrons from one reactant to
another. a.k.a redox reactions
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More Redox
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Introduction to Cellular Respiration
Cellular Respiration is a biochemical process
that aerobically harvests energy from food
molecules in the cell
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Breathing vs Cellular Respiration
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Cellular Respiration is a Redox Process
Oxidation
Reduction
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Cells tap energy from electrons transferred from
organic fuels to oxygen
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Redox reactions release energy when electrons
fall from a hydrogen carrier to Oxygen
At the beginning of the next set of reactions all
the NADH gives up its energetic electrons and
NAD is regenerated
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Electron Transport Chain
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Two Mechanisms Generate ATP
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Chemiosmosis
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Substrate-level Phosphorylation