Lecture 15 (Part 2) Notes: Mitochondria & Energy Production PDF

Lecture 15 (part 2) Notes: Mitochondria & Energy Production Main Functions of Intercellular Compartments: Origin of the Eukaryotic Cells: The Endosymbiotic Theory The endosymbiotic theory (also known as symbiogenesis), is an evolutionary theory of the origin of eukaryotic cells form prokaryo...

Lecture 15 (part 2) Notes: Mitochondria & Energy Production Main Functions of Intercellular Compartments: Origin of the Eukaryotic Cells: The Endosymbiotic Theory The endosymbiotic theory (also known as symbiogenesis), is an evolutionary theory of the origin of eukaryotic cells form prokaryotic organisms First proposed by the Russian botanist Konstantin Mereschkows (1905-1910) and later advanced by with microbiological evidence by Lynn Margulis (1967). This theory holds that the organelles distinguishing eukaryote cells evolved through symbiosis of individual single-celled prokaryotes (bacteria and archaea). Symbiosis (living together): close and long-term biological interaction The theory holds that organelles form eukaryotic cells with two membranes. Like mitochondria and chloroplasts, represent formerly free-living prokaryotes taken one inside the other in endosymbiosis Supporting evidence ○ Binary ssion of mitochondria nad plastids ○ Circular DNA inside these organelles similar to bacteria fi The Big Leap: Energy Supply Mitochondria: Structure and Function Aerobic respiration: converts, in prescience of oxygen, energy stored in food molecules (glucose) into chemical energy stored in ATP This process produces carbon dioxide as a byproduct (waste) CH(0 + 02 CO2 + H , O + ATP carbohydrates (stored energy Outer Mitochondrial Membrane (OMM): ○ Contains many enzymes with diverse metabolic functions and example is monoamine oxidases that breaks down monoamines ingested from food, as well as monoamine neurotransmitters (dopamine and serotonin) ○ The OMM also has porins, which are large channels permeable (passive diffusion) to many molecules when opened (ATP, sucrose) Inner Mitochondrial Membrane (IMM): ○ High protein : lipid ratio (3:1) ○ Double layered folds are called cristae - increase membrane surface area and contain machinery for aerobic respiration and ATP formation ○ Rich in a phospholipid called cardiolipin, which is a characteristic of bacterial membranes and needed for optimal function of many enzymes  The mitochondria also has two aqueous compartments ○ Inter membrane space ○ Matrix: a high protein content, gel-like consistency space containing mitochondrial ribosomes and DNA. In mammals, mitochondrial DNA (mtDNA) encodes a total of 37 genes (13 polypeptides like ATP synthase and cytochrome c oxidase, 22 tRNA, and 2 ribosomal RNA) Mitochondria and Cellular Respiration: Cellular respiration uses chemical energy stored in molecules uncharged as carbohydrates (glucose) and lipids to produce ATP (adenosine triphosphate) Cellular respiration involves a series of catabolic reactions Cellular respiration in presence of oxygen = aerobic respiration Substrate-level phosphorylation: ○ Hydrolysis reaction releases enough energy to drive phosphorylation of ADP to ATP (e.g. glycolysis where a 1 glucose molecule is partially broken down into 2 pyruvate molecules). Oxidative phosphorylation: ○ Chemical energy of organic molecules is transferred rst to electron carriers to create an electrochemical gradient that can power ATP synthesis. fi  Coenzymes acting as electron carriers can exist either as: ○ Oxidized - can accept electrons ○ Reduced - can donate electrons when returning to their oxidized state Nicotinamide adenine dinucleotide ○ Oxidized = NAD+ ○ Reduced = NADH Flavin Adeline dinucleotide ○ Oxidized = FAD ○ Reduced = FADH2 Oxidation of NAHD and FADH2 allows for electrons and energy to be transferred Mitochondria: Oxidative Phosphorylation Oxidative phosphorylation is Stage 4 is animal cell cellular respiration Divided into two steps ○ Step 1: Complexes I-IV ○ Step 2: ATP synthase Step 1: Generate an electrochemical gradient ○ Electron transport through Complexes I-IV and proton (H+) ○ High energy electrons (e-) pass from coenzymes (NADH and FADH2) in the matrix to electron carriers in IMM  ○ Series of intermediate e- carriers (respiratory enzyme complexes I, II, III, IV) = Electron Transport Chain (ETC) ○ Energy transfer at each complex used to pump H+ from matrix into inter membrane space ○ Ultimately, low energy e- is transferred to terminal e- acceptor (O2) resulting in production of H2O Step 2: Proton movement down electrochemical gradient to power ATP synthesis