* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download AP Biology Notes Outline Chapter 9: Cellular Respiration Cellular R
Butyric acid wikipedia , lookup
Nicotinamide adenine dinucleotide wikipedia , lookup
Radical (chemistry) wikipedia , lookup
Fatty acid metabolism wikipedia , lookup
Basal metabolic rate wikipedia , lookup
Metalloprotein wikipedia , lookup
Mitochondrion wikipedia , lookup
Phosphorylation wikipedia , lookup
NADH:ubiquinone oxidoreductase (H+-translocating) wikipedia , lookup
Evolution of metal ions in biological systems wikipedia , lookup
Photosynthesis wikipedia , lookup
Electron transport chain wikipedia , lookup
Adenosine triphosphate wikipedia , lookup
Microbial metabolism wikipedia , lookup
Light-dependent reactions wikipedia , lookup
Photosynthetic reaction centre wikipedia , lookup
Citric acid cycle wikipedia , lookup
Biochemistry wikipedia , lookup
AP Biology Notes Outline Chapter 9: Cellular Respiration Cellular Respiration is the process that releases energy by breaking down food molecules in the presence of oxygen o Organisms that respire: animals, fungi, plants (during night hours) Cellular respiration requires a food molecule (such as glucose), oxygen, and it gives off carbon dioxide Because is occurs in the PRESENCE of OXYGEN, cellular respiration is known as AEROBIC respiration The chemical formula for cellular respiration is: o 6O2 + C6H12O6 → 6 CO2 + 6 H2O + Energy o oxygen + glucose → carbon dioxide + water + energy The reactants of cellular respiration are: o oxygen (O2) & glucose (C6H12O6) The products of cellular respiration are: o carbon dioxide (CO2) and water (H2O) The 3 main stages of cellular respiration are: o Glycolysis o Krebs Cycle (Citric Acid Cycle) o Electron Transport USEFUL ANIMATION: o http://www.sumanasinc.com/webcontent/animations/content/cellularrespiration.html Glycolysis takes place in cytoplasm of cell. The Krebs Cycle and Electron Transport chain take place inside the mitochondria. AP Biology Notes Outline Chapter 9: Cellular Respiration Cellular respiration and fermentation are energy-yielding pathways (catabolic). To understand what happens when a catabolic pathway decomposes glucose, you must first understand: o Redox Reactions: a chemical reaction involving the transfer of one or more electrons from one reactant to another. OXIDATION: loss of electrons from a substance REDUCTION: addition of electrons to a substance As electrons from redox reactions are transferred from one substance to another, energy is transferred as well. o RECALL THAT ELECTRONS HAVE ENERGY! o Oxidized substances LOSE energy o Reduced substances GAIN energy The fate of glucose in the body can take one of two catabolic pathways: o CELLULAR RESPIRATION a.k.a. aerobic respiration absolutely requires oxygen occurs in mitochondria o FERMENTATION occurs without oxygen less efficient than cell respiration (makes less ATP) SUBSTRATE LEVEL PHOSPHORYLATION: Some ATP created during cell respiration is made by direct enzymatic transfer of a phosphate group from a substrate to ADP. OXIDATIVE PHOSPHORYLATION: ATP synthesis can be powered by the flow of H+ back across mitochondrial membrane (chemiosmosis). AP Biology Notes Outline Chapter 9: Cellular Respiration The first set of reactions in cellular respiration is glycolysis: Glycolysis is the process in which 1 molecule of glucose is broken in half, producing 2 molecules of pyruvic acid. Glycolysis occurs in the cytoplasm of the cell. Glycolysis produces a total of 4 ATP, but requires 2 ATP in the beginning to get the pyruvic acid through the membrane of the mitochondria to enter the next phase. Therefore, the NET ATP YIELD of glycolysis is 2 ATP! Glycolysis means “splitting of sugar”. During glycolysis, a six-carbon sugar is split into 2 three-carbon sugars. These smaller sugars are then oxidized (lose electrons) and their remaining atoms rearranged to form 2 molecules of pyruvate. This is a 10-step process, each catalyzed by a specific enzyme…with an energy input and energy payoff phase (Figure 9.8 page 161). The conversion of pyruvate to acetyl CoA is the junction between glycolysis (step 1) and the Krebs cycle (step 2). If oxygen is present, Pyruvate (3 C each) from glycolysis enters the mitochondrion. Using Coenzyme A, each pyruvate is converted into a molecule of Acetyl CoA (2 C each). What happened to the other carbon from each molecule of pyruvate? CO2 released! NAD+ is reduced to form NADH AP Biology Notes Outline Chapter 9: Cellular Respiration In the presence of oxygen, the pyruvic acid produced during glycolysis passes to the second stage of cellular respiration: the Krebs Cycle. o During the Krebs cycle, pyruvic acid is broken down into carbon dioxide in a series of energy-extracting reactions. Every time you exhale, you expel the CO2 produced by the Krebs cycle. For each turn of the 8-step cycle, 5 pairs of high energy electrons are captured by the carrier molecules NADH and FADH2. NADH and FADH2 are energy carriers! They carry electrons captured during the Krebs Cycle (AND THEIR HYDROGENS) to the Electron Transport Chain – so we can make ATP!!! AP Biology Notes Outline Chapter 9: Cellular Respiration Following the Krebs cycle, the electrons captured by NADH and FADH 2 are passed to the electron transport chain. NADH and FADH2 also dump their hydrogen atoms here! o NADH and FADH2 shuttle high-energy electrons extracted from food during glycolysis and the Krebs cycle to an electron transport chain built into the inner mitochondrial membrane. As each complex of the chain accepts and then donates electrons, it pumps hydrogen ions (protons) from the mitochondrial matrix into the inner membrane space – creating a gradient of H+ across the membrane. o The hydrogen ions flow back, down their gradient, through a channel in an ATP synthase (a protien) – causing it to rotate. Each time it rotates, the enzyme ATP synthase grabs a low energy ADP and attaches a phosphate, forming highenergy ATP o The ATP synthase harnesses the proton-motive force to phosphorylate ADP, forming ATP. NOTE: this is oxidative phosphorylation because it is driven by the loss of electrons from food! THE USE OF AN H+ GRADIENT TO TRANSFER ENERGY FROM REDOX REACTIONS TO CELLULAR WORK (ATP) is called CHEMIOSMOSIS. The complete breakdown of 1 glucose molecule through cellular respiration results in the production of 36 molecules of ATP. AP Biology Notes Outline Chapter 9: Cellular Respiration When oxygen is NOT present, glycolysis is followed by a different pathway called fermentation. o Fermentation releases energy from food molecules in the absence of oxygen o Because fermentation does not require oxygen, it is said to be anaerobic The 2 main types of fermentation are: o alcoholic fermentation o lactic acid fermentation Fermentation – aside from the original 2 ATP’s made during glycolysis, the only energy produced is that which is in the bonds of… o ethyl alcohol -- C2H6O o lactic acid – C3H5O3 In the absence of oxygen, a cell will use fermentation to produce ATP by substrate-level phosphorylation. Lactic Acid Fermentation converts glucose into lactic acid. This type of fermentation occurs in human muscle cells during strenuous exercise when breathing cannot supply the cells with enough oxygen. AP Biology Notes Outline Chapter 9: Cellular Respiration Pyruvate is a key juncture in catabolism: o Glycolysis is common to fermentation AND respiration. o The end product of glycolysis is pyruvate…represents a fork in the catabolic pathways of glucose oxidation. o In a cell capable of both respiration and fermentation, pyruvate is committed to one of those two pathways, usually depending on the presence of oxygen. During glycolysis, each glucose molecule is broken down into two molecules of the compound pyruvate. The pyruvate crosses the double membrane of the mitochondrion to enter the matrix. The Krebs cycle decomposes pyruvate into Carbon Dioxide. Don’t forget conversion to Acetyl CoA FIRST!!! Pyruvate is broken down into 3 molecules of CO2…including the molecule of CO2 released during pre-Krebs cycle conversion of pyruvate to acetyl CoA. AP Biology Notes Outline Chapter 9: Cellular Respiration NADH or FADH2 transfers electrons from molecules undergoing glycolysis and the Krebs cycle to the electron transport chains…which are built into the inner mitochondrial membrane. The ETC converts the chemical energy to a form used to drive oxidative phosphorylation. Cycle generates 1 ATP per turn by substrate phosphorylation…but most of the chemical energy is transferred during the redox reactions to NAD+ and FAD. The reduced coenzymes, NADH and FADH2, shuttle their cargo of high-energy electrons to the electron transport chain, which uses the energy to synthesize ATP by oxidative phosphorylation. Electron transport and pumping of protons (H+), which create an H+ gradient across the membrane. The ATP synthase protein complex functions as a mill, powered by the flow of hydrogen ions. This complex resides in the mitochondrial and chloroplast membranes of eukaryotes and in the plasma membranes of prokaryotes. Each of the four parts of ATP synthase consists of a number of polypeptide subunits. CHEMIOSMOSIS IS AN ENERGY-COUPLING MECHANISM!!! ATP synthesis powered by the flow of H+ back across them membrane (CHEMIOSMOSIS).