EX PHYS TEST I I Bioenergetics 1 What is ATP How does it function How is ATP formed ATP is an energy rich compound that stores energy which powers all of the cell s energy requiring processes Potential energy is conserved within the bonds of ATP through food sources This potential energy is then extracted and transferred into chemical energy to power biological work Formation ATP is formed from a triphosphate group a ribose and the nucleotide Adenine ribose adenine adenosine The bonds that link to the outermost phosphates represent high energy bonds because they release considerable amounts of energy during hydrolysis Therefore the hydrolysis of a phosphate form ATP serves as its energy generating mechanism ATP uses this mechanism to donate phosphates in creating new cellular material 2 Differentiate between aerobic and anaerobic metabolism a Aerobic Metabolism that occurs in the presence of oxygen These processes occur in the mitochondria only TCA citric acid cycle and ETC respiratory chain electron transport chain occur through exclusively aerobic conditions oxygen supply is mandatory Aerobic metabolism produces a more prolonged energy source for exercises including marathons swimming walking etc Energy is produced at a slower rate These activities rely on oxygen as a nal electron acceptor so without oxygen exercise is unable to be sustained i Glucose 2 Pyruvate 2 Acetyl CoA 36 ATP b Anaerobic Metabolism that occurs in the absence of oxygen These processes cannot occur in the mitochondria because oxygen isn t available a requirement for this organelle Instead these processes occur in the cytosol These processes include the regulation of phosphocreatine glucose glycogen glycerol and some deaminated amino acids This type of metabolism occurs when an individual is participating in situations where oxygen isn t readily available asthma maximum exercise A large amount of energy is produced but it is quick to fatigue Examples would include sprinting and power training i Glycose 2 Pyruvate 2 ATP Lactate 3 Describe glycolysis Glycolysis includes the breakdown of glucose to two molecules of pyruvate Glycolysis is stimulated when there are high blood glucose levels and the body acts to remove glucose from the blood by breaking it down into pyruvate which can lead to different pathways Glucose is brought into the cell through GLUT 4 Glut 4 is located on the cell membrane stimulated by physical activity and insulin and it allows glucose entry into the sarcoplasm for ATP synthesis TEST QUESTION During aerobic conditions pyruvate oxidizes to acetyl CoA Acetyl coA then acts as a metabolic intermediate as it can enter the TCA cycle providing energy for the cell or be transformed into fatty acids FA synthesis During anaerobic conditions pyruvate is instead reduced to lactic acid which accumulates in the muscles Regulation Glycolysis occurs in the cytoplasm and is regulated by PFK levels of fructose 1 6 bisphosphate oxygen and ATP levels When there are high blood glucose levels such as after a meal glycolysis is stimulated by insulin When there are low blood glucose levels during fasting or exercise gluconeogenesis is stimulated by glucagon Glycolysis is crucial for exercise lasting up to 90 seconds test question a Know net ATP yield depending on substrate used and know what other energetic molecules are formed Net reaction Glucose 2NAD 2ADP 2Pi 2 Pyruvate 2ATP 2NADH 2H 2H2 Glycogen Glucose Pyruvate extra ATP produced with breakdown from 2 ATP produced glycogen 3 ATP produced b How is lactate formed from glycolysis What are the conditions under which it is formed Lactate is formed from pyruvate nal product in glycolysis during anaerobic conditions Lactate builds up during high intensity resistance training or sprinting activities when the body doesn t have an adequate oxygen supply for the given activity This is usually due to the fact that the ETC cannot process all of the hydrogens from NADH when oxygen supply is low These unprocessed hydrogens can then attach to pyruvate and form lactate via lactate dehydrogenase NADH H is oxidized to NAD which serves to continue glycolysis hence why lactate production is so important during activities that rely primarily on carbohydrate metabolism 4 Describe the Krebs Cycle TCA cycle The TCA cycle involves the metabolism of acetyl CoA from pyruvate into several intermediates that serve to produce ATP Acetyl coA is broken down to carbon dioxide 6 molecules and hydrogen atoms 20 within the mitochondria ATP is produced when hydrogen atoms oxidize to water during oxidative phosphorylation in the ETC cycle The primary function is to generate electrons for passage via NADH H and FADH2 in the respiratory chain to NAD and FAD With adequate oxygen supply NAD and FAD regenerate a Know what happens to pyruvate before entering the Krebs cycle Pyruvate is rst oxidized to acetyl CoA by pyruvate dehydrogenase complex THIS REACTION IS IRREVERSIBLE Acetyl CoA considered the universal intermediate between carbohydrates lipids and proteins can then enter the Krebs cycle and produce energy for demanding cells This process requires oxygen and deals with mostly lipolysis and aerobic glycolysis NADH H ATP For each the complete metabolism of one molecule of acetyl CoA o 3 NADH H each NADH releases 3 ATP 3 X 3 9 ATP o 1 FADH2 each FADH2 releases 2 ATP 1 X 2 2 ATP o 1 ATP are produced via substrate phosphorylation b Know what important high energy molecules are formed e g FADH2 1 TOTAL ATP 12 5 For the complete metabolism of glucose This 10 ATP is doubled because one molecule of glucose yields two molecules of acetyl CoA so total glucose metabolism from the TCA cycle would be 24 ATP Know what the role of NADH H and FADH2 in the ETC and the differences in energy yield The electron transport cycle utilizes NADH H and FADH2 as electron carriers which enter the respiratory chain at complexes I and II Each molecule of NAD Niacin containing coenzyme gains a proton and two electrons reducing to NADH H which produces 3 ATP P O ratio 3 Each molecule of FAD ribo avin containing coenzyme gains two hydrogens and two electrons reducing to FADH2 which produces 2 ATP P O ratio 2 a Know the general mechanism by which energy is produced in the ETC Electrons are transferred in the form of protons from NADH and FADH2 to oxygen through the series of electron carriers within the electron transport chain Five cytochromes process the electrons through the respiratory chain to couple reactions that
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