76 Copyright © 2019, IGI Global. Copying or distributing in print or electronic forms without written permission of IGI Global is prohibited. Chapter 4 DOI: 10.4018/978-1-5225-5282-6.ch004 ABSTRACT Mitochondria are a dynamic organelle of the cell involved in the various biological processes. Mitochondria are the site of the adenosine triphosphate (ATP) production, electron transport chain (ETC), oxidation of fatty acids, tricarboxylic acid (TCA), and cellular apoptosis. Besides these, mitochondria are the site of production of reactive oxygen species (ROS), which further disrupts the normal functioning of this organelle also making mitochondria itself as an important target of oxidative stress. Thus, mitochondria serve as an important target in the process of neurodegeneration. In the present chapter, the authors describe mitochondria and its functioning, dynamics, and the mitochondrial dysfunction in aging and neurodegenerative disorders (NDs). INTRODUCTION Mitochondria are the main organelle of the cell which plays key role in the various processes includ- ing oxidative phosphorylation, calcium signaling (Rizzuto et al, 2012), stress responses (Pellegrino & Haynes, 2015) and cellular apoptosis (Bratic & Larsson, 2013). The primary role of mitochondria is the production of ATP by the process of oxidative phosphorylation. During this process some of the elec- trons eventually leaks and this results in the generation of free radicals or reactive oxygen species (ROS) (Payne & Chinnery, 2015). The production of ROS is known to cause the oxidative damage to various components of mitochondrial electron transport chain (ETC) resulting in the mitochondrial dysfunction. Mitochondria dysfunctional is further characterized by decreased activity of ETC complexes, decreased rate of electron transport in complex-I and IV, reduced capacity of oxidative phosphorylation, decreased ATP production, increased water permeability in brain mitochondria, decreased ATP-synthase activity, increased accumulation of oxidative products, decreased mitochondrial membrane potential, increased Mitochondrial Dysfunction in Aging and Neurodegeneration Vaibhav Walia Maharshi Dayanand University, India Munish Garg Maharshi Dayanand University, India