sc chapter 7

reactions that result in energy release

reactions result in the stored or absorbed energy

• refers to the flow of energy change within the human body
• it is concerned mostly with the extraction of energy form charbs fats and proteins
• biochemical conversion of these large molecules is necessarty to extract chemical energy and transfer energy to skeletal muscle contractile proteinds

ithe ability to perform work and energy will chnge in proportion to the magnitude of work performed

energy cannot be created or destroyed but can transform form one form to another

• large amounts of potential energy from storage or food sources can be transferred to fuel muscle performance
• high energy compound
• composed of adenine and ribose (adenosine) linked to three phosphates

• because of its location within skeletal muscle fibers, tends to leak into circulation when muscle damange takes place and serves as an indirect marker muscle damage
• has several isoforms that identify the source of damage skeletal or cardic muscle  or brain

• the boounds that link the outermost two phophatest posses the ability to releas chemical energy
• hdrolysis of pc drives ADP to form atp
• this reaction is catalyzed rapidly by creatine kinase

• skeletal muscle atp stores- the human body has a limited capacity tostore atp and at  anygiven time  can only sustain only a few seconds of exercise so cells must replenish
• phospocreatine pc system
• produce atp from multiple adp sources

• is a high energy phosphgate that provides energy for hig intensity activites lasting up to 5 to 10 seconds
• engaged initially during lowe intensity activites
• concetration within skeletal muscles is four to five times greater thatn atp and more prominent in ft that st fivers
• predominat energy soutce for explosive anaerobice exercise and force declines as pc deplets
• because of limited pc stores the atp pc system cannotprovide sufficient energy to sustain exercise beyond 10mseconds
• operates via this equation
• ADP+ phopocreatine <> atp+ creatine
• suvstantial free energy is released when the bond between creatine and phosphate is cleaved 

• an enzyme adenylate kinase also known as myokinase in skeletal muscle  catalyzes the folowing reaction
• 2ADP<>ATP+AMP

• two adps are dydrolyed to form atp and a molecule of adenosine monophosphate
• the adenlyate kinase reaction augments the muscles ability for rapid energy turnover and produces amp, which is a poten stimulator for glycolysis

• the law of mas action which states chemical reactions taking place in solution progress to the right with the addition of reactants or progress to the left eith the addition of products. eith enzyme mediated reactions the rate of product formation is highly influenced by the amount of reactants
• example: greater amounts of adp formed during exercise increases the rate of ck and adenylated kinase reaction

• anaerobic energy metabolism and the ability to act as an osmotic agent
• when muscle creatine stores increase via supplementation this process attracts water to enter the cells (osmosis) causing increased body weight and muscle protein syntesis
• synthesized itn the body from the amino acids arginine, glycine, and methionine 95% is obsorvbed in skeletal muscles

• is critical to explosivve exerecise perfomance
• high intensity exercise may deplete pc by 60 to 80% during the first 30 seconds with up to 70% depletion taking place withing 12 seconds
• half life ranges form 21 to 57 seconds depending on intensity and volume

• where resynthesis of poc occurs
• a faster followed by a slower componet and the rate of pc reynthesis may be affected by the type of recovery (active vs passive)

• muscle ph
• adp levels
• diphasic response
• ocygen avaiability- are critical during the fast component
• the half life of pc resyntheis is longer when muscle ph decreases
• accumulation of hydrogen inhibits pc resyntheisi primarily during the slow component of recovery
• atp  used to resynthesize pc is derived rom ocidative metabolism and a faster rate of pc reynthesis in st compared to fe fimvers is see
• the kinetics of pc resynthesis is important when determining rest intervals for tr and interval training

• greater subtrate  storage at rest
• altered enzyme activity
• limited accumulation of fatiguing metabolites. repeated bouts of high intensity exercise can increase atp anc pc storage via a supercompensation effect.
• showed a 22% increase in resting pc, 39% increase in muscle creatine and 18% increase in atp concentrations following 5 months of rt

• ck 
• adenylatd kinase or myokinase
• the magnitude of muscle growth is critical when examining enzyme changes
• enzyem activity is expressed relative to total muscle protein content

• is the breakdown of cho to reynthesize atp in the cyoplasm
• another anaerobic metabolic system that can provide energy for high intensity exercise for up to 2 minutes
• the rate of atp resynthesis is not as rapid as pc
• but the human body has a larger glycogen supply so high energy liberation is sutained for a longer period of time
• the free energy released in this series of reaction forms atp and nictiamide adenin dinucleotide.
• glycolysis is a series of 10 reactions breaking down the 6- carbon glucose to a 3 carbon pyruvate the net result is 2 or 3 atp formed (3 atp form muscle glycogen , 2 atp form a molecule of blood glucose

the first 5 steps  consume energy (invest) whereas the second half results in the net gian of atp and NADH

the first step is the formation of glucose-6- phosphate for blood glucose the enzyem kexokinase adds a phophate to gluose so it cannot leave the cell(promotes more glucose uptake into muscle) ths requires atp(glucose mus first enter the cell via a glucose transporter glut)for muscle glycogen, the enzyme phosphorylase breaks a molecule of glucose-1- phosphate (glycogenolysis)

• for muscle glycogen, the enzyme phosphorylase breaks a molecule of glucose-1- phosphate (glycogenolysis)
• this raction does notrequire energy
• at rest phophorylase is inactive (bform) but becomes activated  (a form) during exercise in response to greater epinephrine secretion and elevated calcium concentrations

glucose-6-phosphate must then be converted to fructose 6- phosphate (via isomerase enzyme) and to fructose 1,6 biphosphate

• enzymephophorylates fructose 6 phosphate and is considered the rate limiting reaction of glycolysis
• the regulation of pfk is critical to the magnitude of energy liberation derived form glycolysis
• this reaction requirs energy so up to this point in glycolysis we ahve used 2 atps but have not prodcued any
• this reaction are reversible so glucose could be formed druing gluconeogenesis

a process by which glucose is reformed in the opposite direction of glycolysis

the initial 6 carbon molecule is split via an enzyme aldolase into two 3 carbone molecules, dihydroxyacetone phophate (dhap) and glyceraldehyde 3 phosphate molecules undergo a series of reactions  (where net atp will be formed)

yielding 1,3 bisphosphoglycerate, 3 phosphoglycerate, and 2 phosophoglycerate.

• formation of 2atp and 2nadh
• we now have formed a total of 0atp for glycolysis to this point
• we used 2atp and formed 2 atp, netting 0 atp

phosphoenolpyruvate pep is formed from 2 phosphoglycerate via an enzyme enolase

enzyme enolase and epe then forms pyruvate via the enzyme pyruvate kinase

pyruvate produces 2 atp (one from each pep molecule) thereby  netting 2 atp formed from glycolysis

pyruvate is the end product but can be further mdified to meet metabolic demands

• if inadequate ocygen is present pyruvate can be converted into lactate via the enyzme lactate dehydrogenase (ldh)
• this reaction leads to some accumulation of hydrogen that contributes to muscle fatigue pyruvate can travel to the mitochondria, lose a carbon( forming acetyl coa) and enter the krebs cyle (aerobic respiration)

• accumulation of hydrogen that contributes to muscle fatigue pyruvate can travel to the mitochondria, lose a carbon( forming acetyl coa) and enter the krebs cyle (aerobic respiration
• aerobic and anaerobic glycolysis are not practical beacuse glycolysis is an anerobic process

• is inhibited by sufficient oxygem levels steady state aerobic exercis or during rest
• is stimulated by high concentration s of adp, p, ammonia, and by slight decreases in ph and amp
• intese exercise reults in a marked increase in atp hydrolysis, therbyyielding higher concnertations of adp and p
• ammonia is a byproduct of amp metabolism, and an increase in ammonia stimulates glycolysis
• glycolysis is inhibited by reductions in ph, increased atp, pc, citrate, adn free fatty acids
• high atp and pc levels signify a recovery stat thus furter need for glycolysis is reduced.
• energy substrated can regulate glycolysis via negative feedback wher high concetraiton of atp will limit production
• and enzyme control

enzyme that stores glycogen

• regulate glycolysis via the allosteric unit
• for example: hecokinase is inhibited by glucose 6 phophate
• pfk is inhibited by atp, and hydrogen and stimulated by amp.
• pyruvate kinase is inhibited by atp and acetyl coa aind is timulated by amp and fructose 1,6 bisphophate
• the elaborate negative feedvack control of glycolysis can stimulate or inkibit key glycolytic enzymes based on the energy needs of the human body

• has a negative impact on perfomance
• production of lactate from pyruvate yields hydrogen, which contributes to muscle fatigue.
• accumulation of hydrogen reducest ph and leads to a rapid onsed of fatigue

• athlets with high lactate thresholds are capable of excelling at endurance evetns
• the curve shifts to the right with training at or beyond the lactate threshold indicating  that higher intensity is needed to prodcue a specifc blood lactate level
• circute training can increase lactacte threshold

donates elctrons wheras reduction reactions accept electrons

• converted to lactate
• or converted to actyl coa and co2 via pyruvate dehydrogenase

• majoirity of energy derived aerobically comes form the oxidation of chos and fats with little from protein under normal conditions
• aerobic metabolism occus within the cells mitochndria
• provieds the primary source of atp at rest and during low to moderate steady state exercise
• 70% of atp produced at rest comes form fats wheraes 30% comes from cho
• as exercise intensity increases so does the percent of atp liberation from cho
• high intensity relies predominantly upon cho metabolism
• oxygen is limited until the end of the cycle

removal of hydrogen is critical as hydrogen atoms posses potential energy stored form food sources and these electons are transported and used for atp synthesis

•  powerhouses of the cell
• contain  carrier moleules that oxidize electrons form hydrogen and pass them to oxygen  via reduction reactions that generate a large amount of atp

• is capable of being oxidized and can be formed from fat and protein sources, which makes it the common link of thes fule sources
• two molecules of acetyl coa enter the krebs cycle as two pyruvates are produced in glycolysis

• begins the aerobic system
• involves reactions (that do not require oxygen ) that continue the oxidation of acetyl coa and produces 2atp indirectly
• the goals are to oxidize acetyl groups and attach electrons to the carrier NAD and FAD
• transfers two carbons to ocaloacetate to form the 6 carbon citrate via citrate synthase.
• oxaloacetat is converted iinto isocitrate via conitase
• then a ketoglutarate via isocitrate dhydrogenase
• then succinyl coa via a ketoglutarate dehydrogenase
• then succinate via succinylco synthetase,
• succinate is converted to fumarate via succinate dehydrogenase
• fumarate converted to malate via fumarase
• and to ocaloacetate via malate dehydrogenase

fatty acids can be convertd to acetyl coa

6 molecules of nadh and two molecuels of fadh

couples reactions between electron donors and acceptors across the inner mitochondrial membrane.

hydrogen atoms are passed along the chain of cytochromes in complexes where they reduce oxygen to form water and a proton motive gradien to phosphrylate adp

• 3atp will be produced per molecule of nadh
• 2atp from fadh
• 5 form oxidation/ 2 from blood glucose and 3 from stored glycogen
• 2atp  form the krebs cycle
• 12atp will be produced from 4 nadh
• 22atp wil be produced form the electron transport chain
• total of 38 or 39 atp

fat breakdown via hormone sensitive lipase  into glycerol and three free fatty acids

• lipolysis
• fatty acids can enter circulation or be oxiized from muscle stores  via beta oxidation
• beta oxidation involves the splitting of 2 carbon acyl fragments from a long chaing of fatty acids.
• protons are accepted, water is added, atp  phophorylates the ractions . and acyl fragments form with coenzyme A to yield acetyl coa
• acetyl coa enters the crebs cylce and hydrogen released enters the electrons chains
• 147 atp can be generated per fatty acid
• 441 atp can be genrated  from triglceride

• at increases the number of capillaries surrounding each muscle fiber and capillary density ( number of capillaries relative to muscle csa) by 15%
• increase the number of mitocndria and mitochondrial density in muscle in proportion to traing volume
• increase myoglobin up to 80%

higer capillary content enables greater nutrient and oxygen exhange during exercise  and favors greater reliance on fat metabolism

endurance trained men have 103%greater mitochondrial number and three times greater mitochondrial volume than untriand men

• a protein that binds oxygen in muscle and tranport it ot the mitocondria
• is higest in st fibers and is importan for muscle endurance increases.

• 20.93% oxygen
• .03 co2
• 79.4% nitrogen

• can be mesasured at rest and during exeercise
• resting enenergy expeniture  provieds an estimate of resting metabolic rate

• assumes that gas exchange reults from nutrient breakdown solely
• is a mesasure of co2 produced per unit of O
• give an indication of fuel usage
• RQ=co2prodcued/ o2 consumed
• cho rq is closer or greater then 1
• fat rq .7
• protein or mixed diet rq .82-.86

reflects more accurately the role of anaerobic exercis metabollism during echaustive exercis

• the minimal level of energy needed to sutain bodly funcitons
• represents the individula total energy ependiture in a day

• body mass- the larger the body mass the higher the bmr. lean body mass is a strong component of bmr
• regulare exercis-enhances bmre with themagnitude dependet upon intensity volume, duration and mucle mass involvement
• diet induced thermogenis-increase in bmr associated with digestion absorption and assimilation of nutrients and activation of smphatic system
• environment- warm places produce high bmt

• the difference between oxygen supply and demand
• larger during anaerobic thatn aerobic exercise
• smaller in aerobically traind athelets thatn untraind individuals and strenght power athletes

• the additional oxygen consumed over basline leves  following exercise
• consist of a rapid intial component followed by a slow component