20018
Besides the obvious relevance of mitochondria in energy production , calcium homeostasis , and reactive oxygen species ( ROS ) production , new processes like mitochondrial fusion / fission , phosphorylation and nitrosylation modifications in mitochondrial proteins have been suggested to form part of a cast of key players in cardiac disease .
 oxygen
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 oxygen