CELLULAR RESPIRATION

Glycolysis  Releases a small amount of energy  This is a process that takes one molecule of glucose and breaks it in half which produces two molecules of pyruvic acid  2 molecules of ATP are used up in order for this process to take place and 4 are produced at the end of this process, therefore glycolysis has a net gain of 2 molecules of ATP  If oxygen is present it leads to two other pathways that release a great deal of energy, if oxygen is not present glycolysis is followed by a different pathway

No Oxygen Present  When there isn’t any oxygen (known as anaerobic), glycolysis is followed by a process called fermentation  There are two main types of fermentation: alcoholic and lactic acid

Fermentation  Yeasts and some microorganisms use this type  Ethyl alcohol and carbon dioxide are waste (sometimes NAD + is also in this category)  Ex: when bread starts to rise, CO 2 forms bubbles in the bread to make it rise  This process regenerates NAD +  This is produced in your muscles during rapid exercise when the body cannot supply enough oxygen AlcoholicLactic Acid

Oxygen is Present  About 90% of the chemical energy that was available in glucose is still unused and the only way to release it is through oxygen  When oxygen is present (aerobic) glycolysis is followed by the Krebs cycle and the electron transport chain  These three processes make up a process called cellular respiration

Cellular Respiration  The process which occurs within mitochondria in which cells use oxygen to burn sugar for fuel (re- = back‚ again; spira = to breathe)  The equation is: 6O 2 + C 6 H 12 O 6 6CO 2 + 6H Energy

The Krebs Cycle  The 2 nd stage of cellular respiration  Pyruvic acid is broken down into carbon dioxide in a series of energy-extracting reactions  It begins when pyruvic acid produced by glycolysis enters the mitochondria  It gets broken down and carbon dioxide gets released (its what we breathe out) and the ATP that is produced can then be used of cellular activities (for every turn of the cycle, one ATP molecule is produced)  NADH and FADH 2 are released into the 3 rd stage

Electron Transport Chain  This takes place in the inner mitochondrial membrane  NADH and FADH 2 are passed along through this chain  At the end of this chain is an enzyme that combines these electrons with hydrogen and oxygen to form water

The Totals  Remember glycolysis produces 2 molecules of ATP (in the absence of oxygen that is all that gets produced)  The Krebs cycle and electron transport chain enable the cell to produce 34 more molecules of ATP (this means that 18 times more ATP is produced during aerobic respiration)  The 36 molecules of ATP produced represent 38% of the total energy of glucose (the rest is heat)

Cellular Respiration Song  When your cells burn sugar fuel from your meal (such a deal!), there are three parts to the job and you get some ATP.  First you do glycolysis. Split that sugar right in half, and you make two ATPs: store some energy.  Second comes the Kreb’s cycle, break it down to CO 2 in your mitochondria, and you make more ATP.  Third, your mitochondria transport those electrons. Grab their energy to make lots and lots of ATP.  Then you dump those electrons and some extra hydrogen. Bond them onto oxygen and you get some water.  Forty total ATPs: glycolysis uses two, and eukaryotes use two more so the total’s thirty-six.