Photosynthesis and cellular respiration provide energy for lifeBreathing supplies oxygen to our cells for use in cellular respiration and removes carbon dioxideCellular respiration banks energy in ATP moleculesThe human body uses energy from ATP for all its actvivites• Kilocalories (kcal)- An Energy unit, the quantity of heat required to raise the temperature of 1 kilogram (kg) of water by 1 degree Celsius. degree Celsius.Cells tap energy from electrons “falling” from organic fuels to oxygenRedox reaction occurring simultaneouslyOverview: Cellular respiration occurs in three main stagesGlycolysis harvests chemical energy by oxidizing glucose to pyruvateEnergy investment phaseEnergy payoff phasePyruvate is chemically groomed for the citric acid cycleThe citric acid cycle completes the oxidation of organic molecules, generating many NADH and FADH2 moleculesMost ATP production occurs by oxidative phosphorylationCertain poisons interrupt critical events in cellular respirationReview: Each molecule of glucose yields many molecules of ATPFermentation enables cells to produce ATP without oxygenLactic Acid FermentationAlcohol FermentationGlycolysis evolved early in the history of life on earth• Glycolysis is the universal energy-harvesting process of life• Significant levels of O2 did not accumulate in the atmosphere until about 2.7 billions years the atmosphere until about 2.7 billions years ago• For almost a billion years, prokaryotes must have generated ATP exclusively from glycolysis, because it does not require O2Cells use many kinds of organic molecules as fuel for cellular respirationFood molecules provide raw materials for
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