12-09: Energy From Food

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Chemical Potential Energy

• food energy is stored by the relatively high potential energy of electrons in the bonds of molecules like glucose compared to the low potential energy of electrons in bonds of molecules like carbon dioxide and water
• cellular respiration releases that energy and transfers it to the bonds of ATP molecules

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Redox Reactions

• oxidation is the process of losing electrons
• reduction is the process of gaining electrons
• redox reactions involve both
  • all of cellular respiration depends on electron transfer - when an electron moves to a more electronegative molecule
• oxidizing agents are reduced, reducing agents are oxidized

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Respiration Redox

• oxidation = the removal of hydrogen

• reduction = the gaining of hydrogen

  

Combustion vs. Controlled Oxidation

• combustion = a rapid oxidation of fuel (like glucose)

• for cellular purposes a stepwise, controlled process provides every to carrier molecules that are then used to make ATP

• if a sugar is combusted - the energy is thermal/heat → do not want this for cellular processes

  

Energy Carriers

• nicotinamide adenine dinucleotide (NAD+) & flavin adenine dinucleotide (FAD) are coenzymes, the help the enzymes catalyze the oxidation of glucose

• NAD+ and FAD are energy carriers used in the oxidation of food

• dehydrogenase enzymes remove hydrogen ions (oxidize) and pass them to carriers which get reduced

  

  

Aerobic Cellular Respiration

• this process extracts energy from glucose with oxygen producing ATP

• it is divided into 4 stages - it starts in the cytoplasm and most occur in the mitochondria

• glycolysis → pyruvate oxidation → citric acid cycle → electron transport chain

  

Mitochondrial Map

• glycolysis: cytoplasm/cytosol (liquid)
• pyruvate oxidation and the citric acid cycle: matrix
• electron transfer chain: inner membrane

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Aerobic vs. Anaerobic Respiration

• energy can be produced without oxygen via fermentation but it is much less efficient and produces toxic byproducts