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Lecture 8

BIO1140 Lecture 8: Mitochondria

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University of Ottawa
Caroline Petit- Turcotte

Mitochondria -the energetics of mitochondria (important role) -ATP is not all they do -wll address in detail and continue on Friday -attention to learning objectives -mitochondria does more than just ATP: Mitochondria is involved in multiple metabolic processes, will not look at all of that—there’s a course called metabolism for that -But what else can it do? -The role it plays as meditators of cellular stress (at the cellular level) -What is stress for a cell and how might it respond -Calcium and how mitochondria is intimately involved with calcium -cell death—Friday Think about chloroplasts—the organelles that accomplish photosynthesis, but what else do they accomplish? -The structure has features that other organelles do not have: double membrane, inner has cristae (specific organization where it’s invaginated) -different types, components and portions of the cells; so far in the tool box of techniques include: microscopy, FRAP, freeze-fracture, now there is a new tool: different types of centrifugation -one of the tools to deal with a situation What is the main advantage of cristae? ANSWER: Perhaps the folds—or the cristae may be more efficient for the mitochondria to absorb or rid their nutrients -the way the mitochondria is built and organized: cristae; what is the advantage? To increase the amount of surface area, to allow more area for the electron transport chain to occur, allowing more ATP to produce. And a chain of complex proteins to build the hydrogen gradient, to power the wonderful structure at the end of the chain. How is it made? The blue portion is the rotor and the mobile subunits are the mobile portions. trying to move the bottom parts that phosphorylates from ATP to ADP. How do we get it to move? -uses the hydrogen gradient, hydrogen pumps through the protein (hallow), 10 individual protein subunits that assemble together to form the C portion that forms to build the F0 portion of the F0, F1 ATPase—each time, -one of the 10 subunits, makes contact with the A subunit, hydrogen flows through, moving within the membrane (it turns) and there are no covalent bonds -everytime H goes through, 3 at a time, able to have the F1 unit in the matrix, move a portion of the entire rotation and allows to phosphorylate ATP to ADP. This portion B is the stater and it is not moving. The mobile parts are the c, gamma and epsilon. It is embedded in the inner mitochondrial membrane and what phosphorylates ATP to ADP is in the matrix—when it is made, it’s in the matrix. -protein gradient is between the 2 membranes Membrane transport and active transport. Is this an F-type? Uses ions and ATP. Does it comply with active transport? Now the H is going down or against it’s concentration gradient? It’s going down it’s transport, so do you need active transport? No, but it can accomplish active transport and is an F-type pump. Can accomplish because the pump works in reverse. -Can hydrolyze ATP, and use energy to pump H back into the intermembrane space against the gradient. Does accomplish active transport, but not when doing ATP synthesis, although it is the same protein. -Can relate to secondary, tertiary and amino acid structures. Metabolism—just the elements that relate to ATP synthesis. -Krebbs cycle -Glycolysis -oxidative phosphorylation -many other metabolic activities that occur in the mitochondria (no need to know them) -need to know the goal with respect to ATP synthesis -must be able to talk about photosynthesis and the mechanisms above; no need to know the info about all the electrons, etc. -many mitochondria in the cell, not all have the same number, nor do they keep the same amount throughout their lives -glycolysis does not occur in mitochondria but in the cytoplasm -the end are 2 pyruvates, and those 2 we need to get inside the mitochondria to accomplish ATP. In order to produce more, when already accomplishing, we get 2 out of it per glucose molecules, but it’s not a good pay off—must be a way to get more out of it. what do we do with them (2 pyruvates)? AS glucose to pyruvate, already broken up molecules, free electrons, electron carriers (NADH to shuttle energy to mitochondria) and pyruvate will get inside mitochondria, must cross both membranes and can serve as the fuel for the crebs cycle, but must convert to ACETYL COA before the krebs will begging and once completed, will give more electron carriers, NADH and FADH and 2 more ATP. Still not that great. All electrons will power the electron transport chain, will build the H gradient, powering the ATPase. What is the goal of transporting all of the electrons from glycolysis to the crebs cycle? What is the purpose of carrying all those electrons from glycolysis, pyruvate oxidation and Krebs cycle? A- Use those electrons to power the production of ATP? B- Use those electrons to build a hydrogen gradient that powers the FoF1ATPase C- Use those electrons as a buffer in the mitochondrial matrix D- Use those electrons as energy in the mitochondria for protein synthesis ANSWER: B—Use those electrons to build a hydrogen gradient that powers the F0F1ATPase Glycolysis—oxidation of pyruvate, krebs, breakdown of molecules, high energy electrons, taken to carry each individual components of the electron transport chain. The more can carry the ATPase, can produce ATP. Will need more maximum efficiency. Glycolysis -break down one glucose—the payoff is 2 of those carriers, 2 hydrogens and 10 ATP 10 reactions that make up glycolysis—no need to remember for this course -focus on what implication for what this has for the cell—a cell biology course -same with the Krebs cycle, don’t memorize the structure and every step—what is the cells implication? Each pyruvate, going to produce Acetyl Coa, power the 8 biochemical reactions and get 2 electrochemical carriers to power up the gradient -do not memorize the biochemical reactions -FADH, NADH and ATP out of it -each glycolysis gives 2 pyruvates, get to go around twice Compare/contrast ATP synthesis in chloroplas
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