Why are Mitochondria Essential for Life? (original) (raw)

Mitochondria as we don't know them

Trends in Biochemical Sciences, 2002

Biochemistry textbooks depict mitochondria as oxygen-dependent organelles, but many mitochondria can produce ATP without using any oxygen. In fact, several other types of mitochondria exist and they occur in highly diverse groups of eukaryotes - protists as well as metazoans - and possess an often overlooked diversity of pathways to deal with the electrons resulting from carbohydrate oxidation. These anaerobically functioning mitochondria produce ATP with the help of proton-pumping electron transport, but they do not need oxygen to do so. Recent advances in understanding of mitochondrial biochemistry provide many surprises and furthermore, give insights into the evolutionary history of ATP-producing organelles.

Mitochondria Revisited. Alternative Functions of Mitochondria

Bioscience Reports, 1997

This review explores the alternative functions of mitochondria inside the cell. In a general picture of mitochondrial functioning, the importance and uniqueness of these intrinsic functions make them irreplaceable by other intracellular compartments. Among these are, participation in apoptosis and cellular proliferation, regulation of the cellular redox state and level of second messengers, heme and steroid syntheses, production and transmission of a transmembrane potential, detoxication and heat production. In most of the listed functions, reactive oxygen species modulate a number of non-destructive cellular activities. Some of the mitochondrial functions are reviewed in detail.

Mitochondria: isolation, structure and function

The Journal of Physiology, 2011

Mitochondria are complex organelles constantly undergoing processes of fusion and fission, processes that not only modulate their morphology, but also their function. Yet the assessment of mitochondrial function in skeletal muscle often involves mechanical isolation of the mitochondria, a process which disrupts their normally heterogeneous branching structure and yields relatively homogeneous spherical organelles. Alternatively, methods have been used where the sarcolemma is permeabilized and mitochondrial morphology is preserved, but both methods face the downside that they remove potential influences of the intracellular milieu on mitochondrial function. Importantly, recent evidence shows that the fragmented mitochondrial morphology resulting from routine mitochondrial isolation procedures used with skeletal muscle alters key indices of function in a manner qualitatively similar to mitochondria undergoing fission in vivo. Although these results warrant caution when interpreting data obtained with mitochondria isolated from skeletal muscle, they also suggest that isolated mitochondrial preparations might present a useful way of interrogating the stress resistance of mitochondria. More importantly, these new findings underscore the empirical value of studying mitochondrial function in minimally disruptive experimental preparations. In this review, we briefly discuss several considerations and hypotheses emerging from this work.

Mitochondria at the extremes: pioneers, protectorates, protagonists

Extreme physiology & medicine, 2014

The engulfment of a proto-mitochondrion by a primitive unicellular organism gave rise to the first eukaryotic cell, and ever since, mitochondrial function has been a vital aspect of eukaryotic life. Under conditions of physiological stress, the mitochondrion is far from a passive bystander, instead playing a key role in signalling pathways and the cellular responses they elicit. In this thematic series of Extreme Physiology & Medicine, the role of the mitochondrion in the response to physiological stress will be considered anew, through research articles, reviews, viewpoints and methodology papers that aim to reposition the organelle as a key player in the human response to a wide range of extreme conditions.

Functional Mitochondria in Health and Disease

Frontiers in endocrinology, 2017

The ability to rapidly adapt cellular bioenergetic capabilities to meet rapidly changing environmental conditions is mandatory for normal cellular function and for cancer progression. Any loss of this adaptive response has the potential to compromise cellular function and render the cell more susceptible to external stressors such as oxidative stress, radiation, chemotherapeutic drugs, and hypoxia. Mitochondria play a vital role in bioenergetic and biosynthetic pathways and can rapidly adjust to meet the metabolic needs of the cell. Increased demand is met by mitochondrial biogenesis and fusion of individual mitochondria into dynamic networks, whereas a decrease in demand results in the removal of superfluous mitochondria through fission and mitophagy. Effective communication between nucleus and mitochondria (mito-nuclear cross talk), involving the generation of different mitochondrial stress signals as well as the nuclear stress response pathways to deal with these stressors, maint...