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Lecture 8

Lecture 8 - Mitochondria

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Western University
Biology 2601A/B
Graeme Taylor

LECTURE 8 – MITOCHONDRIA  “Powerhouses” of the cell  Main function is to provide the energy necessary for cellular function  Primary role of mitochondria is to produce the energy molecule known as ATP Mitochondrial Structure  Outer membrane and inner membrane  Inner membrane – incredibly folded – folds are known as cristae o To increase surface area of mitochondrial inner membrane  Aerobic energy production occurs through enzymes that are within those inner membranes – more surface area results in efficient energy production  Within inner membrane, the matrix can also be found – citric acid cycle occurs here  Mitochondria have their own genome which is completely independent from the nuclear genome  Also have their own ribosomes – transcription and translation of mitochondrial DNA occur within the mitochondria  Mitochondria have different shapes – don’t always look like bean-shaped organisms that they are classically illustrated as  Can fuse together and take on various shapes Mitochondrial DNA  Mitochondrial genome is small compared to nuclear genome  Only encodes 37 genes in humans  Maternally inherited in most species, including humans  Evolves 10 times faster than nuclear DNA because of its size – exposed to more danger so it evolves faster Endosymbiotic Theory  Ancestral prokaryotic cells, containing a plasma membrane and no nucleus, originally only produced energy through glycolysis.  Through engulfing of other cells, these prokaryotes greatly increased in size as their plasma membrane enfolded in on itself, forming the basis for the nuclear envelope and later, the endoplasmic reticulum  Aerobic bacteria were the first prokaryotes of their kind to utili2e O to extract more energy as ATP. It was through the engulfing of aerobic bacteria by a eukaryotic cell that endosymbiosis became a reality  Eukaryotic cell did not digest engulfed aerobe immediately, it took the waste products of glycolysis and made ATP from that. The ancestral eukaryote was now able to engage in oxidative metabolism, as well as glycolysis Glycolysis  First pathway of cellular respiration – converts 1 molecule of glucose into 2 pyruvate  Ancient, yet wasteful process o Generates little ATP and most energy is contained within pyruvate and NADH molecules – not used Electron Transport Chain  Part of the final process of oxidative metabolism and occurs embedded in the inner mitochondrial membrane (along the cristae)  All structures involved in transport of electrons (ubiquinone, Cytochrome C and other complexes) are linked together in function. This process takes NADH molecules and extracts energy from them ultimately in the form of ATP.  An NADH molecule is oxidized to NAD , whereby it donates its pair of electrons to complex I and onto the ubiquinone where it is shuttled to complex III. Here the pair of electron is shuttle by Cytochrome C to complex IV where it binds with O 2n the process of reducing it to water. Redox Potential and Transfer of Energy  S
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