BIOLOGICAL BATTERIESMitochondria, often called the powerhouse of the cell, is a biological battery that could one daypower small portable devices like mobile phones or laptops.Mitochondrial charge comes from the difference of potential between inner and outermitochondrial membrane. What we call respiratory chain is a biological system meant to separateelectrons from their atoms, thus pumping electrons on one side of a membrane, while protons areleft on the other side, creating a charge (polarization). Unlike our batteries (based on lithium),the mitochondrion uses hydrogen ions (protons).In the mitochondrial electron transport chain electrons move from an electron donor (NADH orQH2) to a terminal electron acceptor (oxygen) via a series of redox reactions. The resultingtransmembrane proton gradient is used to make ATP via ATP synthase ( oxidativephosphorylation). This is called the chemiosmotic coupling hypothesis which was proposed byPeter D. Mitchell (Nobel Prize in chemistry). Electron transport chain and oxidativephosphoylation are coupled by a proton gradient across the inner mitochondrial membrane.The efflux of protons from the mitochondrial matrix creates an electrochemical gradient. This gradient is used by theATP synthase complex to make ATP (energy).
The generic image of mitochondrial electron separation is shown in this picture.Mitochondria convert fatty acids and pyruvate, formed from the digestion of sugars and fats,to adenosine triphosphate (ATP), the cells energy supply. Along the way a tiny electrical currentis generated.Shelley Minteer and coworkers from Saint Louis University in Missouri, US, have been able togather the flowing electrons and put them to work in a new biological battery.Minteer notes that commercially available batteries contain metals, and need to be recycled.However, battery recycling facilities arent widespread in many areas. My research is abouttransitioning from these metal-based batteries to a biological battery, she said. The living celldoes energy conversion very efficiently. Her research in organelle-based bioelectrocatalysis is focused on the use of mitochondria tocatalyze the complete oxidation of pyruvate and fatty acids at the anode of fuel cells as well asthe unique biochemical properties of mitochondria that allow it to be used in biological energyuse .Similar to a traditional battery, the bio version contains two electrodes. The cathode houses theconversion of oxygen to water, while the anode holds the immobilised mitochondria. Once thesubstrate comes in it can be completely oxidised to carbon dioxide, and when that happens,electrons go through the wire and do work.The bio battery is completely renewable and biodegradable, and is stable at room temperatureand a neutral pH for up to 60 days.Other groups are trying to replicate the electrocytes used by the electric eel.The research began by studying the biochemistry of eel voltage generation, based on ionchannels. The researchers were able to replicate artificial ion channel models for power outputand energy conversion.How do mitochondria store energy?
Almost everybody agrees that younger people and children possess more energy than the elderly.Until recently this empiric observation could not be explained in scientific terms. Sincemitochondrial medicine was launched in the 2000, much has been clarified in terms of thiscellular powerhouse. It is a common knowledge now that cells contain from a few to thousandsof mitochondria, depending on their energy needs. Because mitochondrial DNA is prone to moredamage than the nuclear DNA and has fewer repair capabilities, mitochondria are being depletedas we age. The reason elderly have less energy than young people and children is because theyhave fewer mitochondria. Neuronal mitochondria are depleted even more because the brainlacks sufficient antioxidant mechanisms. The CNS uses 25% of the body oxygen, but it does nothave a proportionally increased concentration of antioxidants to counter this load. As such, thebrain is vulnerable to high levels of oxidative stress.Mitochondria, the main target of oxidative stress in susceptible neurons, were found to besignificantly decreased in number in Alzheimer’s Disease (AD), suggesting that oxidative stressmay be fundamental to the development of this neurodegenerative disease. Additionally theabsence of neurofibrillary tangles in neurons exhibiting mitochondrial damage and energydeficiency places mitochondrial abnormalities as the earliest cytopathological changes in AD.Another common change is the reduced numbers of microtubules in AD, which impairmitochondrial transport to the axon. The structural and functional abnormalities, found inneurons lacking neurofibrillary tangles, confirm that mitochondrial damage is a primarypathology of Alzheimer’s disease.(Brain Protection in Schizophrenia and Mood Disorders,Michael S. Ritsner, 2010).The mitochondrial energy is stored in hundreds or thousands of mitochondria per cell multipliedby trillions of cells. This clean energy could very soon power our computers, cameras and somehome devices.ADONIS SFERA, MD