Lesson 14 Aerobic Respiration Photosynthesis generates organic molecules and O2 that power Cellular Respiration which releases ATP and generates CO2 and H2O Electron transfer reactions are called Redox reactions need electron carrier to carry electrons o Transfer of electrons during chemical reactions releases energy stored in organic molecules this energy released is ultimately used to synthesis ATP o Energy from catabolism exergonic releases ATP H2O o Energy for cellular work endergonic releases ADP P1 o Oxidation removal of electrons from ions or molecules Electrons donor is called the reducing agent Of organic molecules lead to loss of C H or C C bonds o Reduction adding electrons to ions on molecules the amount of positive charge is reduced Electron receptor is called the oxidizing agent Of organic molecules lead to a gain of C H or C C bonds Catabolic pathways yield energy o The breakdown of organic molecules is exergonic o Fermentation is a partial degradation of sugars that occurs without O2 o Aerobic respiration consumes organic molecules and O2 and yields ATP o Cellular respiration includes both aerobic and anaerobic respiration Occurs in the mitochondion Glucose is oxidized O2 is reduced Glycolysis breaks down glucose into 2 molecules of pyruvate o small amounts of ATP is formed by substrate level phosphorylation uses an enzyme to catalyze the regeneration of ATP o Generates 2 pyruvate 2 H2O 2 ATP 2 NADH 2H o During glycolysis partial oxidation of glucose to form 2 pyruvic acids molecules electrons removed are added to the electron carrier NAD 2 NAD are reduced to 2 NADH energy released by partial oxidation of glucose converts 2ADP 2 PO4 2 ATP o Two major phases 1 Energy investment phase 2 ATP is used one by hexokinase other by phosphofructokinase 2 Energy payoff phase 4 ATP made two by phosphoglycerokinase two by pyruvate kinase o in the presence of O2 pyruvate enters the mitochondrion where oxidation of glucose is completed o before citric acid cycle can being pyruvate must be converted to acetyl CoA this step is carried out by a multienzyme complex that catalyzes 3 reactions releases CO2 2 NADH Citric acid cycle Krebs cycle completes the breakdown of pyruvate to CO2 o The cycle oxidizes organic fuel from pyruvate generating 1 ATP 2 CO2 3 NADH 1 FADH2 per turn o Acetyl CoA joins cycle by combining with oxaloacetate forming citrate Oxidative phosphorylation accounts for most of the ATP synthesis because it is powered by redox reactions o NADH and FADH2 accounts for most of the energy extracted these 2 electron carriers donate electrons the ETC which powers ATP synthesis o Electron transport chain generates NO ATP directly function is to break the large free energy drop from food to O2 into smaller steps that release energy in a manageable amounts Is in the inner membrane cristae of the mitochondrion Most of the chain s components are multiprotein complexes The carriers alternate reduced and oxidized states as they accept and donate electrons Electrons drop in free energy as they do down the chain are finally passed to O2 forming H2O Electrons are transferred from NADH or FADH2 to ETC Each NADH reduced form of NAD represents stored energy to synthesize ATP and also passes the electrons to the ETC Electron transport in the ETC causes proteins to pump H from the mitochondrial matric to the intermembrane space this concentrates H in the intermembrane space H then moves back across the membrane passing through the proton ATP synthase o This is an example of chemiosmosis the use of energy in a H gradient to drive cellular work At the end FAD and NAD are reformed e leaving are added to H and O2 to produce H2O o During cellular respiration energy flows glucose NADH ETC proton motive force ATP 30 32 o Fatty acids are broken down by beta oxidation and yield acetyl CoA NADH and FADH2 o Pacemaker of cellular respiration allosteric enzyme phosphofructokinase o ATP concentration begins to drop respiration speeds up when there is plenty of ATP respiration slows Feedback inhibition down Lesson 15 Anaerobic respiration Without O2 ETC will cease to operate In that case glycolysis couples with fermentation or anaerobic respiration to produce ATP Anaerobic respiration uses ETC with final electron acceptor other than O2 ex Sulfate pyruvate acetaldehyde Fermentation uses substrate level phosphorylation instead of an ETC to generate ATP consists of glycolysis reactions that regenerate NAD which can be reused 1 Alcohol fermentation Pyruvate ethanol CO2 Used in brewing winemaking and baking 2 Lactic acid fermentation Pyruvate reduced to NADH lactate Used by muscle cells with O2 is scarce Obligate anaerobes carry out fermentation or anaerobic respiration and CANNOT survive in the presence of O2 Facultative anaerobes can survive using either fermentation or cellular respiration PYRUVATE is the fork in metabolic road that leads to two alternative catabolic routes Evolutionary significance ancient prokaryotes are thought to have used glycolysis long before there was O 2 in the atmosphere therefore early prokaryotes could ONLY use glycolysis to generate ATP Lesson 16 17 Photosynthesis Photosynthesis the process that converts solar energy into chemical energy 6 CO2 12 H2O Light energy C6H12O6 6 O2 6 H2O Is redox process in which H2O is oxidized and CO2 is reduced o H2O s electrons are transferred along with H to CO2 to reduce it to sugar In an endergonic process energy boost provided by light Consists of the light reactions and Calvin cycle o Light reactions in the thylakoids Split H2O Release O2 Reduce NADP to NADPH Generate ATP from ADP by photophosphorylation o Calvin cycle in the stroma Forms sugar from CO2 using ATP and NADPH Begins with carbon fixation this cycle builds sugars from smaller molecules by using ATP and the reducing power of electrons carried by NADPH carbon enters the cycle as CO2 and leaves as the sugar glyceraldehyde 3 phosphate G3P for next synthesis of 1 G3P the cycle must take place 3 times fixing 3 molecules of CO2 ATP and electrons from NADPH generated during the light reaction generate G3P which is also the same carbon sugar formed in glycolysis by the splitting of glucose Three phases Carbon fixation catalyzed by rubisco o CO2 is added to RuBP by the enzyme rubisco o Alternate mechanism have evolved in hot arid climates On hot dry days plants close stomata which conserves H2O but also limits photosynthesis Closing of stomata reduces access to CO2 and causes O2 to
View Full Document
Unlocking...