Respiration CAQ

🫁 Respiration Describe the role of NAD and FAD Organic molecules such as glucose oxidised during glycolysis, link reaction and Krebs Cycle and the electrons and protons from oxidation are transferred to the coenzyme NAD and FAD in order to reduce them to NADH and FADH2 respectively They serve as mobile electron and proton car to carry the high energy electrons and protons from these organic molecules to the electron transport chain and thus re-oxidising themself The high energy electrons in NADH and FADH2 are used to reduce electron carriers of the electron transport chain and the coenzymes reoxidises themself to form NAD to FAD The high energy electrons release energy as they are passed down the electron transport chain in order to provide energy for the electron carriers to actively pump protons from the mitochondrial matrix to the inter membrane space against its concentration gradient, establishing a proton gradient due to the impermeability of the inner mitochondria membrane, which is important for ATP synthesis as this series of redox reactions is coupled to phosphorylation of ADP to form ATP Re-oxidation of NADH and FADH2 allows regeneration of NAD and FAD, allowing it to pick up more protons and electrons from Krebs cycle, link reaction and glycolysis in order to continue the reactions Each reduced NAD yields 3 ATP Each reduced FAD in the matrix yield 2 ATP through oxidative phosphorylation During anaerobic respiration, re-oxidation of NaDH allows regeneration of NAD during fermentation to allow glycolysis to continue in order to produce ATP in absence of oxygen R espiration 1

The high energy electrons from NADH and FADH2 combines with oxygen, a final electron acceptor to form water During anaerobic respiration, electrons from NADH reduces pyruvate in the presence of lactate dehydrogenase to form lactate amd it also reduces ethanal in the presence of CO2 with ethanol Describe main stages of Krebs cycle Takes place in the mitochondrial matrix and when oxygen is present Acetyl coA 2C produced during the link reaction combines with oxaloacetate(4C) to form citrate 6C Citrate is decarboxylated and dehydrogenated to form, alpha-ketoglutarate 5C and NADH Each decarboxylation results in a loss of carbon to form CO2 Regeneration of oxaloacetate involves decarboxylation and dehydrogenation to yield 2 NADH and 1 FADH2 and 1 CO2 Electrons from glucose transferred to electron carriers NAD and FAD in order to reduce them NAD  2H  2e  NADH  H (or reduced NAD FAD  2H  2e  FADH (or reduced FAD 1 ATP is also produced through substrate-level phosphorylation during this regeneration process All carbon in glucose lost as carbon dioxide Overall,1 molecule of glucose forms 6 NADH, 2 FADH2 and 2 ATP as Krebs cycle occurs twice per glucose molecule. How ATP is produced during anaerobic respiration / why does anerobic respiration only yield a small amount of ATP/ why only glycolysis occurs in anaerobic respiration / why does it yield a small amount of ATP R espiration 2

takes place in absence of oxygen which serves as a final electron acceptor in electron transport chain Without oxygen, no final electron acceptor for oxidative phosphorylation, both link reaction and Krebs cycle subsequently stop as NAD cannot be regenerated from NADH in mitochondrion as NADH and FADH2 unable to donate its electrons to the electron transport chain hence no electron carriers to be regenerated, movement of electrons along etc inhibited, no more electrochemical proton gradient and hence ATP cannot be synthesised by oxidative phosphorylation, no proton pumping Hence, glucose not completely oxidised to form CO2 and water and energy is still trapped in the ethanol/lactate Anaerobic respiration takes place in the cytoplasm of the cell via only glycolysis to produce a net of 2 ATP molecules per glucose via substrate level phosphorylation for each glucose molecule oxidised Pyruvate undergoes alcoholic fermentation whereby it is decarboxylated to ethanal and then reduced by pyruvate dehydrogenase and pyruvate decarboxylase to ethanol and carbon dioxide respectively with the regeneration of NAD in yeast In mammal, lactate fermentation occurs where NAD regenerated as electrons in NADH is used to reduce pyruvate with lactate dehydrogenase to lactate NAD regenerated in both processes ensures steady supply of NAD is used for glycolysis to continue hence only glycolysis occurs only Role of oxygen in aerobic respiration Acts as a final electron acceptor at the end of electron transport chain where it will combine with electrons and protons to form water By removing electrons, oxygen re-oxidises electron transport chain so that NADH and FADH2 can continue to donate electrons to the chain, thereby allowing oxidative phosphorylation to continue to produce ATP R espiration 3

This allows regeneration of NAD and FAD allowing them to pick up more electrons and protons from glycolysis, link reaction and Krebs cycle to keep them going Why more glucose is required during anaerobic respiration/ less glucose used in aerobic respiration? Under aerobic conditions, complete breakdown of glucose produces 38 ATP molecules per glucose molecule compared to 2 AtP molecules in anaerobic conditions Under anaerobic respiration, 19 glucose molecules will be needed to generate the same amount of energy that 1 glucose can produce in aerobic respiration Under aerobic conditions, link reaction and Krebs cycle produce NADH that will be oxidised and hence regenerated by the electron transport chain during oxidative phosphorylation, generating additional ATP However, under anaerobic conditions, glycolysis only produces a net of 2 ATP molecules for each glucose molecule oxidised and NAD is only regenerated through fermentation process to allow only glycolysis to continue. Link reaction and Krebs cycle are unable to continue due to absence of oxygen, a final electron acceptor, to regenerate NAD and FAD so electrons remain in NADH and FADH2 and unable to carry more electrons from these reactions. Effect of ATP on PFK activity High ATP concentration leads to an inhibition of PFK activity ATP acts as an allosteric inhibitor and bind to allosteric site of PFK, inducing a conformational change in the 3D conformation of PFK such that substrate is no longer complementary in shape and charge to active site, stabilises inactive conformation of PFK, reducing affinity for fructose 6-phosphate Decreases rate of glycolysis as lesser glucose molecules converted to substrate, lesser pyruvate formed Why is anaerobic respiration unsustainable for the muscles in the long run? R espiration 4

Anaerobic respiration only yields a net gain of 2 ATP molecules per molecule of glucose peer glycolysis which is an inefficient form of energy release as compared to 38 ATP per glucose molecule in aerobic respiration which is not enough to provide great energy demands and can deplete energy storage of glycogen and fats Under anaerobic conditions, lactate fermentation occurs where pyruvate molecules converted to lactic acid to regenerate NAD from NADH in order for glycolysis to continue Continuous production of lactic acid causes accumulation of lactic acid in muscle causing muscle fatigues and muscle aches Outline the process of aerobic respiration occurs when food substances such as carbohydrates are oxidised to provide energy, protons and electrons in order to produce ATP Oxygen is required for the complete oxidation of food substances and to produce large amounts of ATP Glycolysis occurs in the cytoplasm of the eukaryotic cell Phosphorylation of glucose involves in the initial investment of 2 ATP molecules which phosphorylate glucose molecules to form fructose-1, 6- bisohosphate catalysed by phosphofructokinase which then cleaves to from 2 molecules of glyceraldehyde-3-phosphate G3P 3C G3P undergoes oxidation by dehydrogenatiom