Cellular Respiration Cellular respiration is the process that releases energy by breaking down glucose and other food molecules in the presence of oxygen In biology and chemistry, energy is referred to as calories Formally, calories are the amount of energy needed to raise the temperature of 1g of water by 1 degree Celsius There are 1000 regular calories in 1 food calorie
Glycolysis The first step in cellular respiration of sugars is glycolysis 1x molecule of glucose (a sugar), along with 2x ATP and 2x NAD + (an electron carrier) enter the glycolysis pathway These are turned into 2 molecules of pyruvate (a 3-carbon sugar), 4x ATP, and 2x NADH. Look carefully how many net molecules of ATP are produced?
Glycolysis Because glycolysis does not require oxygen, this is the principal means prokaryotes and smaller organisms produce energy. This is also how your body quickly mobilizes energy for high intensity activity, like sprints
Fates of Pyruvate Without oxygen, pyruvate is either converted to alcohol or lactic acid in order to regenerate NAD + for use in glycolysis. Alcohol Fermentation Lactic Acid Fermentation
Anaerobic Respiration Fermentation regenerates NAD + so glycolysis can continue This whole process is known as anaerobic respiration, or the production of ATP without the use of oxygen!
Aerobic Respiration But, there is a finite amount of NAD + in the cell. As a result, glycolysis can t support long durations of activity, like running a marathon Glycolysis simply can t keep up with the energy demand Aerobic respiration involves the use of oxygen and can convert more efficiently convert sugars (and thus pyruvate) into ATP
Aerobic Respiration Glucose Glycolysis Pyruvate NADH Without Oxygen Fermentation Pathways (Alcohol and Lactic Acid)
Aerobic Respiration Glycolysis Pyruvate NADH 36-38x ATP Glucose With Oxygen Converted to Acetyl-CoA Enters the Krebs Cycle Releases Carbon Dioxide Enters the Electron Transport Chain NADH and FADH
Aerobic Respiration Remember this organelle? Glycolysis takes place in the cytoplasm, but the processes for aerobic respiration take place in the mitochondria
The Kreb s Cycle In order to enter the Kreb s Cycle, pyruvate must be converted to acetyl- CoA Note this produces carbon dioxide and another molecule of NADH
The Kreb s Cycle Acetyl-CoA then enters the Kreb s cycle, where the energy in it is transferred to the electron carriers NAD + and FAD +
The Kreb s Cycle The electron carriers turn into NADH and FADH 2, and move on to the electron transport chain. 1x ATP is produced
The Kreb s Cycle Each pyruvate molecule in the Kreb s cycle will produce 4x NADH, 1x FADH 2 and 1x ATP Because each glucose molecule is broken down into 2 pyruvate molecules, the net for each glucose molecule is 8x NADH, 1x FADH 2, and 2x ATP
Cellular Respiration of Sugar The chemical equation for cellular respiration is as follows 6 O 2 + C 6 H 12 O 6 6 CO 2 + 6 H 2 O + Energy 6 molecules of oxygen plus 1 molecule of glucose yields 6 molecules of carbon dioxide, 6 molecules of water, and energy in the form of ATP
Remember this??? Excited Electron Electron Transport Chain 5. When an excited electron goes through the electron transport chain, it causes many hydrogen atoms (yellow circles) to go across the thylakoid membrane
The Mitochondrial Electron Transport Chain The NADH and FADH 2 from glycolysis and the Krebs cycle transfer their energy here, causing hydrogen ions to be pumped across the mitochondrial membrane.
Light Dependent Reaction ATP Synthase ATP ADP Once across the membrane, just like photosynthesis, the hydrogen ions move across ATP synthase to produce ATP.
The Importance of Oxygen Oxygen is the terminal (final) electron acceptor and is split to form water. ½ O 2 + 2H + + 2e - H 2 O
Aerobic respirations can sustain long bouts of activity because it produces much more ATP than glycolysis. But without oxygen, aerobic respiration can not take place.