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Today we zealously rushed through notes even though everyone was rather sluggish due to a weekend filled with homecoming festivities. Our teacher lectured the class on the oxidation of pyruvate, the Krebs cycle, and the beginning of the electron transport chain.
The following will be a summary of the main points of the topics touched upon in class:
The oxidation of pyruvate takes place after glycolysis and occurs in the membrane of the mitochondria. This second stage in cellular respiration converts two molecules of pyruvate into two molecules of acetyl CoA. Also, two ATP and 2 NADH molecules are produced. The next stage in cellular respiration is the Krebs cycle, sometimes called the citric acid cycle. The krebs cycle takes place in the mitochondrial matrix. During this stage, 2 molecules of acetyl CoA are converted to 8 NADH and 2 FADH2, as well as 2 ATP. Carbon dioxide is released (CO2 is fully oxidized). The final stage in cellular respiration is the electron transport chain, which occurs in the mitochondria. The electron carriers, NADH and FADH2 give their electrons to membrane proteins. These proteins in return uses the energy to pump H+ into the intermembrane space creating a concentration gradient. H+ flows through the concentration gradient and into ATP synthase to produce ATP. All in all, 36 ATP are produced (minus the first two that were used to begin glycolysis) in order to power cellular work.
Don’t forget—NADH and FADH2 are reduced coenzymes that store energy. They play a huge role in producing ATP in the electron transport stage of cellular respiration.
Now for some outside thinking: why do cells produce ATP? In order to do work. The cells that produce the most ATP are muscle and nerve cells, the ones that perform the most work.
What would happen if a cell did not have oxygen to utilize the stages of cellular respiration past glycolysis. Not much. The cell could produce some trivial amounts of ATP, but not enough. For example when muscles work they need energy. When there is a lack of oxygen, and thus a lack of energy, the muscle becomes fatigued and soreness from the accumulation of lactic acid sets in (due to lactic acid fermentation).
photo courtesy Meredith Snookums on flickr.com
Here is a good website link to supplement your studying of cellular respiration–http://www.phschool.com/science/biology_place/biocoach/cellresp/intro.html
