Download Substrate-Level Phosphorylation vs. Oxidative Phosphorylation

Substrate-Level Phosphorylation vs. Oxidative Phosphorylation
ATP is main molecule providing the energy for the cells to do their everyday work. An average person may have
about 250 g of ATP in their cells, but because it is recycled (and recycled very quickly) a person may turn over this
stock 160 times on a lazy day.
There are other molecules that the body can use, but they are less useful. The beauty of ATP is that ATP is
relatively unstable and so the energy required to hydrolyze the phosphoanhydride bond is not exceedingly large.
Breaking the bond produces a more stable ADP. Because the bond can be easily broken, it can also be easily put
back together so this makes recycling very easy.
There are 2 ways that ATP molecules can be made. One is more of a process and the other is more like a reaction.
Definitions Recap:
Phosphorylation – the transfer of a phosphate group off of ATP and onto some other molecule.
Kinases- enzymes that catalyze phosphorylation reactions
Two Ways to Make ATP:
1. Substrate-Level Phosphorylation:
• Occurs in both glycolysis and the citric acid cycle
• The synthesis of ATP by the direct transfer of a phosphate group from some molecule that already had it
(called a substrate) to a molecule of ADP (or GDP)
• The reaction is catalyzed by a kinase
• End result is ATP
• Generalized substrate-level phosphorylation:
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Substrate-level phosphorylation in glycolysis.
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Oxidative Phosphorylation:
Uses O2 to oxidize the electron carriers NADH & FADH2 in order to generate ATP
ATP is made by a mechanical process. ADP & Pi are smashed together in ATP synthase.
Occurs in electron transport chain on the mitochondrial inner membrane
Water is produced in this process as O2 is reduced.