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Energy (chapter 4). Metabolism. the chemical processes occurring within a living cell or organism. anabolic (building up or synthetic) catabolic (tearing down or degradative) . Anaerobic metabolism. occurs without oxygen. Aerobic metabolism.
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Metabolism the chemical processes occurring within a living cell or organism. anabolic (building up or synthetic) catabolic (tearing down or degradative)
Anaerobic metabolism occurs without oxygen
Aerobic metabolism requires free oxygen (which functions as the final electron acceptor during the generation of ATP).
Metabolic pathways Substrates enter the reaction End products remain after the reaction In some cases intermediates are formed Substrate Enzyme 1 > Intermediate Enzyme 2 > End Product
Enzymes speed up reactions that would normally occur are not used up in the reaction work (usually) for both the forward and reverse reactions are specific a property that is based on the shape of the enzyme and thus activity is sensitive to temperature, pH, and amount of the substrate (lock and key mechanism).
Energy - the ability to do work Kinetic - energy that is associated with motion Potential - energy that is stored as is available for use resulting from an object’s location or position (like water behind a dam). Chemical potential energy is stored in the bonds between atoms of a molecule or compound. Thermal- heat energy
The First Law of Thermodynamics states that energy can neither by created or destroyed but it can change from one form to another
The Second Law of Thermodynamics states that during transformations, some or all of the energy is spontaneously converted from more ordered forms to less ordered forms (thus entropy or disorder increases
The Sun Is the ultimate source of energy for life on Earth is the Sun. Energy transfer is not complete (most is lost as heat remember entropy increases) from one tropic (feeding) level to another. Thus energy is a limiting resource
Metabolic Reactions Most metabolic reactions are reversible and tend to run spontaneously toward chemical equilibrium.Photosynthesis and aerobic respiration are two important and necessary processes for energy conversion.
Oxidation-Reduction Reactions involve the transfer of one or more electrons from a donor molecule to an acceptor molecule. The donor molecule is oxidized. The acceptor molecule is reduced. Photosynthesis and respiration consist of these types of reactions.
ATP (adenosine triphosphate) the universal energy currency of all cells energy is stored within the bonds of this energy intermediate (ADP + Pi ATP) The formation of ATP occurs by a process known as phosphorylation (oxidative or substrate-level)
Respiration and Fermentation
Aerobic Respiration Aerobic respiration occurs in the presence of Oxygen. There are four steps: glycolysis, preparation for the Kreb’s cycle, Kreb’s cycle, and the Electron Transport System. The glucose molecule is dismantled during the first three steps and the energy contained within it is transferred directly (Substrate Level Phosphorylation) or indirectly (Oxidative phosphorylation) to ATP. The Carbons of glucose (C6H12O6) are ultimately lost as waste (CO2), the Hydrogens attach to NAD+ or FAD+, and the Oxygens are either lost as waste (combined with the Cs) or have other functions.
Glycolysis Part I is actually an anaerobic reaction. During glycolysis there are 4 ATP molecules formed (by substrate level phosphorylation or our abbrev. slp). There are also two NADH molecules formed from two NAD+ molecules (when the NAD+ s are reduced). These are transported to mitochondria (in eukaryotes) for the electron transfer system.
Glycolysis Part 2 Glycolysis uses two ATP molecules so that the net gain is only 2 ATPs. In aerobic respiration there will be more ATPs formed from glycolysis because of the NADH molecules and the ETS. Each molecule of glucose is broken down into two pyruvates
Glycolysis Part 3 Overall Equation: Glucose + 2ATPs + 2 NAD+ 2 pyruvates + 4 ATPs + 2 NADH (in the presence of oxygen)
Prep for the Kreb’s cycle Each pyruvate now enters a mitochondrion and loses one carbon (and two Oxygens thus CO2 is formed). The remaining two carbon acetyl group attaches to a molecule of coenzyme A (CoA) formed acetyl CoA. A molecule of NADH is also formed for each pyruvate Equation: Pyruvate + NAD+ + CoA acetyl CoA + CO2 + NADH
Kreb’s cycle acetyl CoA is combined with a 4 carbons compound (oxaloacetic acid) to form citric acid. This molecule of citric acid is then rearranged several times until ultimately two molecules of CO2 and one four carbon compound are formed. This is the same as the original four carbon compound and it is now able to bind another acetyl CoA. By the time the Kreb’s cycle has gone through two turns, the entire glucose molecule has been totally dismantled. Equation: Acetyl CoA + oxaloacetic acid + NAD+ + FAD+ + ADP 2CO2 + oxaloacetic acid + CoA + 1 ATP + 3NADH + 1FADH2
Electron Transport System accepts the NADHs and the FADH2s formed during the preceding steps (figure 4-33). Through a series of redox reactions involving H+ ions, energy is released and ATP molecules (usually 34) are formed; by electron transport phosphorylation). Oxygen acts as the final electron acceptor at the end of the ETS. Equation: NADH + FADH2 + ADP + ETS molecules + O2 NAD+ + FAD+ + ATP (@34) + H2O + ETS molecules
Fermentation occurs in the absence of oxygen. Equation: Carbohydrate (e.g., glucose) + NADH reduced carbohydrate + NAD+ + ATP The reduced carbohydrates include ethanol and lactic acid.
