LESSON 14 Describe an oxidation and reduction reaction o What is the oxidizing agent o What is the reducing agent The electron receptor is called the oxidizing agent Explain the principles of a redox reaction The electron donor is called the reducing agent o Some redox reactions do not transfer electrons but change the electron sharing in covalent bonds Ex The reaction between methane and O2 o Electrons Often lead to loss of C H or C C covalent bonds oxidation of glucose releases o o Oxidation of organic molecules energy to form ATP Usually exergonic G spontaneous o Reduction of organic molecules Often lead to a gain of C H or C C covalent bonds Usually endergonic G nonspontaneous o What are electron carriers A molecule capable of accepting one or more than one electrons from another molecule electron donor and then ferry these electrons to donate to another during the process of electron transport NAD FAD o What is NAD and why is it important NAD nicotinamide adenine dinucleotide Electrons from organic compounds are usually first transferred to NAD a coenzyme As an electron acceptor NAD functions as an oxidizing agent during cellular respiration Each NADH the reduced form of NAD represents stored energy that is tapped to synthesize ATP Describe the catabolic pathways involved in producing ATP o Several processes are central to cellular respiration and related pathways 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 Ex Oxidation of glucose in the presence of O2 o Anaerobic respiration is similar to aerobic respiration but consumes compounds other o Catabolic pathways funnel electrons from many kinds of organic molecules into cellular than O2 respiration Glycolysis accepts a wide range of carbohydrates Proteins must be digested to amino acids amino groups can feed glycolysis or the citric acid cycle Deamination of the amino acids must occur first producing ammonia urea and other waste products Fats are digested to glycerol used in glycolysis and fatty acids used in generating acetyl CoA Fatty acids are broken down by beta oxidation and yield acetyl CoA NADH and FADH2 o An oxidized gram of fat produces more than twice as much ATP as an oxidized gram of carbohydrate because of their chemical structure and high energy level of their electrons compared to carbohydrates o Explain the overall reaction to cellular respiration o Harvesting energy from glucose o What are the three stages to cellular respiration Glycolysis breaks down glucose into two molecules of pyruvate Oxidative phosphorylation accounts for most of the ATP synthesis The citric acid cycle completes the breakdown of glucose o How many ATP are generated in each stage Glycolysis Net of 2 4 total produced Citric Acid Cycle 2 1 per each pyruvate Oxidative Phosphorylation 26 28 o Where do these stages occur in the cell Glycolysis Cytosol Citric Acid Cycle Mitochondria Oxidative Phosphorylation Mitochondria Require O2 Citric Acid Cycle Oxidative Phosphorylation Do not require O2 Glycolysis o Which stage s require O2 Which stage s do not require O2 Explain the difference between oxidative phosphorylation and substrate level phosphorylation o Oxidative Phosphorylation The process that generates most of the ATP is called oxidative phosphorylation because it is powered by redox reactions Oxidative phosphorylation accounts for almost 90 of the ATP generated by cellular respiration o Substrate level phosphorylation A smaller amount of ATP is formed in glycolysis and the citric acid cycle by substrate level phosphorylation Uses an enzyme to catalyze the regeneration of ATP o Note for each molecule of glucose degraded to CO2 and water by respiration the cell makes up to 32 molecules of ATP Explain the steps involved in glycolysis o Glycolysis splitting of sugar breaks down glucose into two molecules of pyruvate o Glycolysis occurs with or without O2 present in the cytoplasm and has two major phases Energy investment phase 2 ATP is used one by hexokinase another by phosphofructokinase 5 Energy payoff phase 4 ATP made two by phosphoglycerokinase two more by pyruvate kinase Triose phosphate dehydrogenase During glycolysis o Partial oxidation of glucose to form 2 pyruvic acid molecules loss of C C and C H bonds o Electrons removed from glucose by oxidation are added to the electron carrier NAD 2 NAD are reduced to 2 NADH o Energy released by partial oxidation of glucose converts 2 ADP 2 PO4 2 ATP o What are the two major phases of this stage Energy investment phase 2 ATP is used one by hexokinase another by phosphofructokinase Energy payoff phase 4 ATP made two by phosphoglycerokinase two more by pyruvate kinase o What is are used in this stage Energy investment phase o What is are produced in this stage Energy payoff phase 2 ATP is used one by hexokinase another by phosphofructokinase 4 ATP made two by phosphoglycerokinase two more by pyruvate kinase Results of glycolysis Summary 2 pyruvate molecules 2 H2O 2 ATP molecules 2 NADH 2H Note O2 is not required in glycolysis and CO2 is not generated o Which enzymes use or produce ATP Hexokinase Phosphofructokinase Phosphoglycerokinase pyruvate kinase Describe how glycolysis is linked to the citric acid cycle o In the presence of O2 pyruvate enters the mitochondrion in eukaryotic cells where the oxidation of glucose is completed o Before the citric acid cycle can begin pyruvate must be converted to acetyl Coenzyme A acetyl CoA which links glycolysis to the citric acid cycle o What is are produced as a result o This step is carried out by a multienzyme complex that catalyses three reactions o Note pyruvate first enters into the mitchondrion before it is converted to acetyl CoA One pyruvate molecule is used to produce acetyl CoA The byproducts of the process include NADH H NAH is reduced CO2 is produced Explain the citric acid cycle o The citric acid cycle also called the Krebs cycle completes the break down of pyruvate to CO2 FADH2 per turn Takes place within the mitochondrial matrix o The cycle oxidizes organic fuel derived from pyruvate generating 1 ATP 3 NADH and 1 Partial oxidation breaks C C bonds and releases CO2 Electrons from oxidation of pyruvic acid are added to NAD and FAD to form NADH and FADH2 respectively 1 ATP is assembled from ADP PO4 from energy released by oxidation o Since 1 molecule of glucose produces 2 molecules of pyruvic acid 2
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