. Advantages and Disadvantages of Aerobic Metabolism i. What are the advantages
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Question
. Advantages and Disadvantages of Aerobic Metabolism i. What are the advantages and the disadvantages of aerobic catabolism compared to anaerobic catabolism? (2 pts) [answer here] ii. What are examples of reactive oxygen species which are produced as side products of aerobic catabolism? (2 pts) answer here] iii. Identify the steps/reactions in the organism for dealing with the unwanted effects/by-products of aerobic catabolism and regeneration of the components needed to maintain these processes. Identify these biochemical reactions and the enzymes required for these steps. (5 pt) [answer here] iv. What is the link between the Pentose Phosphate Pathway and dealing with the unwanted effects/byproducts of aerobic catabolism? Explain. (3 pts) [answer here] Mutations in an enzyme called superoxide dismutase are associated with the neurodegenerative disease amyotrophic lateral sclerosis (ALS). Why did researchers initially believe that loss of superoxide dismutase activity would lead to damage to neurons. v. Activated neutrophils and macrophages fight invading bacteria by releasing superoxide, 02 - . These cells contain and NADPH oxidase that catalyzes the reaction 2 O2 + NADPH ? 2 O2-+ NADP+ + Hta what would you expect to happen to the flux through the oxidative steps of pentose phosphate pathway in these cells when fighting invading bacteria? Explain (3 pts) v. answer here]Explanation / Answer
i) One of the biggest advantages of aerobic catabolism over anaerobic catabolism is that the former is more effective in terms of energy production. In aerobic catabolism, which is in presence of oxygen, there is production of more ATP molecules than anaerobic catabolism, which takes place in absence of oxygen. For example, a single molecule of glucose aerobically produces 36 or 38 molecules of ATP while anaerobically only 2 molecules of ATP are generated.
Disadvantage of aerobic catabolism over anaerobic catabolism is the requirement of oxygen for it to take place. Moreover, it does not bring about quick release of energy and leads to production of free radicals.
ii) An unavoidable outcome of aerobic catabolism is the production of Reactive oxygen species (ROS) like superoxide anion (O2•?), hydroxyl radical (•OH), and additionally non-radical atoms like singlet oxygen (O), hydrogen peroxide (H2O2), etc. The molecular oxygen (O2) involved in aerobic catabolism is reduced in a step wise manner by passing through electron transport chain and this generates a number of highly reactive ROS.
iii) Aerobic catabolism produces reactive oxygen species (ROS) which can lead to the oxidative stress and alter the redox homeostasis. Cells employ a number of strategies to combat the oxidative stress and maintain its redox potential. Tri-peptide Glutathione (GSH) and its oxidised form GSSG act as redox couple buffer and maintain negative reducing potential of the cytosol. Also, high catalytic activity enzymes such as superoxide dismutase (SOD), peroxisomal catalase (CAT), glutathione peroxidise (GPx) scavenge the ROS as they are produced.
SOD
O2•? ---------------------------------------------> H2O2
CAT
H2O2-----------------------------------------------------> O2 + H2O
GPx
GSH + H2O2------------------------------------------------------> GSSH + 2H2O
The oxidised GSSH is regenerated back to reduced GSH form using NADPH which may be supplied by Pentose Phosphate Pathway (PPP
iv) ROS inhibits the enzymes like glyceraldehydes 3- phosphate dehydrogenase and pyruvate kinase involves in glycolytic pathway. This diverts the glucose 6 phosphate towards oxidative arm of Pentose Phosphate Pathway (PPP). PPP generates NADPH which provides the reducing power to aid the proteins involved in antioxidant systems and also recycles the oxidised glutathione.
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