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York University
Kinesiology & Health Science
KINE 1020
Kuk/ Riddell

Chapter 18 -Energy Metabolism and Bioenergetics • It is the flow of energy i a biological system resulting in the ability to do work, produce heat etc. • Important Fact- body chemical energy i converted to thermal( heat) and mechanical energy(work) through chemical reactions • Exergonic reactions- energy releasing reactions ( free energy - negative delta G) G refers to the net energy in the system • i.e breaking down ATP or Glycolysis (-96.2k/mol) • Releasing energy creates overall reduction in the net energy left in the system • Endergonic Reaction- energy consuming reaction( free energy- positive delta G) i.e Producing ATP • • Catabolic- breakdown of larger molecules into smaller molecules. i.e. breaking ATP- ADP+Pi • Anabolic - making larger molecules from smaller molecules i.e. synthesis ATP from ADP and Pi Chapter 19- Energy Systems • Biological energy systems: phosphagen system, glycolysis, and oxidative phosphorylation • All produce ATP but at different capacities i.e how much and how fast ATP was created • Adenosine Triphosphate ( ATP) - metabolic currency in biological tissues • Food energy need to be converted to ATP in • Body is machine to do work. Food is dollar bills to feed the machine and ATP is quarter. Food is converted to ATP for the body for work. • Metabolic pathways convert food into ATP • 7.3 k/mol each ATP. Considered an intermediate level energy substrate • During muscle contraction, myosin ATPase hydrolyzes ATP so that energy is released as mechanical movement(25%) and heat (75%) • ATP levels in biological tissues such as muscle stay relatively constant, and even fatiguing intense exercise ATP levels remain within 10-15% of baseline levels. • You cannot get more ATP with enhancements and the ATP you have during muscle contraction must be restored at the same rate. • If this doesn't happen, then the work rate will decrease Aerobic- oxygen Anaerobic- no oxygen • • ATP-Phosphocreatine (PCr) - does not require oxygen and doesn't produce lactic acid but supplies 6-8 seconds of energy • The muscle uses ATP immediately present in the muscle . Only 2-3 seconds worth of ATP You can use ATP-PCr to reform ATP from PCr and ADP rapidly • • Used for activities less than 10 seconds with lots of energy • Occurs in the sarcoplasm. Allowing the recharge of ATP • ATP+Cr ---creatine kinase------ADP +PCr+ H+ (bi-directional equation) • During muscle contraction, there is an increase in the concentration of ADP and hydrogen ions and decrease in the ATP thus if PCr is available, the equation below will be driven from right to left to restore ATP levels to equilibrium • Alternatively, when PCr levels are low, two ADP molecules can form ATP and AMP. However, this reaction does not use up the excess hydrogen ions created from the breakdown of ATP, which is still problematic • 2ADP------adenylate kinase or myokinase -----ATP +AMP • Glycolysis- anaerobic energy source that can provide energy for a longer period of time than ATP-PCr but a slower rate • ATPPCr and glycolysis provide the most (60%) of energy for activities less than 2 minutes of all-out activity • Occurs in the sarcoplasm and the rate is limited by the activity of phosphofructokinase PFK converting fructoe-6-phosphate to fructose 1,6 biphosphate • Anaerobic Glycolysis- the conversion of muscle glycogen to G6P is catalyze by glycogen phosphorylase • The conversion of pyruvate to muscle lactate is catalyzed by lactate dehydrogenase • The capacity for anaerobic glycolysis to produce energy is related to the amount of muscle glycogen available • The amount of of lactate that is produce and accumulates in the muscle is a major factor • Aerobic Glycolysis- Blood glucose is used to produce G6P catalyzed by hexokinase • Blood glucose is a source substrate and not is not limited like muscle glucose • Blood glucose is restored more easily and faster than muscle glucose from the liver or with dietary intake • Calcium and insulin are factors that help blood glucose to enter aerobic glycolysis • If acetyl-CoA increases there will be a negative feedback on glycolysis which limits the potential for aerobic exercise • Oxygen amount in mitochondria is important for acetyl-CoA to continue down the metabolic pathway • Insufficient amount of NADH will also limit entry of pyruvate into mitochondria • Lactic
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