Glycolysis and Anaerobic Cellular Respiration PDF

CELLULAR RESPIRATION Anaerobic vs. Anaerobic  In order for a cell to do work it needs to free ATP from the food it ingests (heterotroph) or produces (autotroph). All food is ultimately converted into glucose which is used to power the cell. The glucose must be processed to recoup the solar ene...

CELLULAR RESPIRATION Anaerobic vs. Anaerobic  In order for a cell to do work it needs to free ATP from the food it ingests (heterotroph) or produces (autotroph). All food is ultimately converted into glucose which is used to power the cell. The glucose must be processed to recoup the solar energy that was captured to fuel its manufacture. The energy in the glucose is converted directly into ATP and into high energy electron carriers that can power production of more ATP. Overall Reaction of Cellular Respiration:  ALL living things undergo cellular respiration The main site of cellular respiration in the cell is the mitochondria (aka the Powerhouse of the cell) which makes energy in the form of ATP BUT, some organisms live in AND, some organisms do environments without oxygen! not have mitochondria! So, then how do ALL living things undergo cellular respiration???  Aerobic Respiration = Cellular respiration with the presence of oxygen Anaerobic Respiration = Cellular respiration without the presence of oxygen  Part 1: Glycolysis Anaerobic Process But the first step in processing glucose in both aerobic & anaerobic cellular respiration  The first step in collecting the energy from glucose is a process that occurs in all cells, glycolysis. Glycolysis occurs in the cytoplasm of all cells and is an organised series of reactions to split glucose. If it stops, the cell runs out of ATP quickly. Glucose is a very stable molecule so an input of energy is required to destabilize the molecule so that the energy can be harvested. The energy from glucose is used to directly build ATP through substrate level phosphorylation and to build the high energy electron carrier, NADH. Video: Substrate level phosphorylation vs. oxidative phosphorylation Glycolysis occurs in two distinct phases, 1. The prep phase destabilizes and splits the glucose. 2. The payoff phase of x2 for EACH G3P glycolysis allows for energy to be made (more than what was used in the prep phase) 1) The prep phase destabilizes and splits the glucose into two molecules of G3P. Step 1: Add phosphate to destabilize glucose. Step 2: Isomerase to rearrange molecule to further destabilize. Step 3: Add phosphate to destabilize molecule for split. Step 4: Split into two End Result of separate Part 1: 2-ATP are three carbon molecules. USED Step 5: 2 G3P molecules Isomerize to change DHAP to G3P for further processing. created  2) The payoff phase of glycolysis allows for energy to be harvested, making back what was invested & more. Step 6: Add phosphate & make NADH. This harvests some of the usable energy. *redox reaction Step 7: Make ATP & harvest more of the energy. *substrate-level phosphorylation Step 8: Rearrange molecule to destabilize so more energy can be harvested. Step 9: Remove water to destabilize molecule further. Step 10: Make ATP by harvesting energy. *substrate-level phosphorylation End Result of Part 2: End Result of Part 2: For 1 glucose (2 G3P): For 1 G3P: 1-NADH created 2-NADH created 2-ATP created 4-ATP created 1 pyruvate created 2 pyruvate created Video: Molecular View of the Glycolysis Reactions  NET Result of Glycolysis: for every molecule of glucose, 2 net ATP 2 NADH Will be processed further 2 pyruvate molecules Net Result: Costs two ATP but you produce four ATP along with two NADH. Pyruvate is toxic to the cell & must be removed quickly. Sketching Glycolysis  Anaerobic Respiration How to deal with the toxic Pyruvate? Pyruvate - 3 different pathways If no oxygen is available, cells can obtain energy through the process of anaerobic respiration. ANAEROBIC RESPIRATION- Fermentation A common anaerobic process is fermentation. Fermentation is not an efficient process and results in the formation of far fewer ATP molecules than aerobic respiration. Fermentation is a short sequence of reactions that uses the energy trapped in NADH to process the pyruvate into a form that can be disposed of. This process does not create any additional energy from the molecule and in fact, uses up the high energy electron carrier molecules produced by glycolysis. There are two primary fermentation processes: 1. Lactic Acid Fermentation 2. Alcohol Fermentation  Lactic Acid Fermentation Occurs when oxygen is not available. For example, in muscle tissues during rapid and vigorous exercise, muscle cells may be depleted of oxygen. They then switch from respiration to fermentation. The pyruvate formed during glycolysis is broken down to lactic acid and energy is released Glucose → Pyruvic acid → Lactic acid + energy  Eukaryotic animal cells deal with pyruvate when there is an increased energy demand coupled with a limited oxygen supply. Animal muscle cells produce lactic acid during exercise and export the acid into the bloodstream. When oxygen is available, lactic acid goes through a series of reactions in the liver and is converted into glucose again. Video Lactic Acid Fermentation Note: New research suggests that the pain associated with lactic acid buildup in muscles may not be due to lactic acid. Alcohol Fermentation occurs in yeasts and some bacteria. Pyruvate formed during glycolysis and is broken down to produce alcohol (ethanol) and carbon dioxide and is released. Pyruvate → alcohol + carbon dioxide + energy Video Alcohol Fermentation Some Uses of Fermentation Yogurt Soy sauce Cheese Vinegar Bread Olives/Pickles Beer Wine/ Ale Sauerkraut Malt