Exam 1 Review Sheet KIN 3306 Physiology of Human Performance Foundation Lecture Bioenergetics Definitions of bioenergetics homeostasis steady state Bioenergetics is the study of energy flow in a biological system For the purposes of this class the energy flow we will be tracking is associated with ATP and the biological system is the human body Homeostasis is defined as the maintenance of a relatively constant internal environment at rest This term can be applied to almost any physiologic variable For example at rest heart rate remains at a relatively constant level The typical resting heart rate is between 70 80 bpm Also please note that relatively constant means that the selected variable is fluctuating around a mean value Steady state refers to the relatively constant internal environment that is achieved during exercise at a fixed intensity For example if you starting running on the treadmill at 6 mph after about 3 5 minutes your heart rate would reach a steady state It is likely your heart rate response would be between 150 170 bpm and fluctuate about a mean value Structure of ATP where energy is held In humans and many other mammals adenosine triphosphate or ATP for short is the most important high energy storage molecule in the body An ATP molecule is composed of three parts The first part is the adenosine backbone Adenosine is not metabolized but rather serves as a foundation to bind phosphate groups and store free energy The second component is the three phosphate groups which are bound to adenosine and each other The bonds between phosphate groups are the storage location of free energy The 1st bond which is located between the 3rd and 2nd phosphate groups is the most important in terms of exercise Contracting skeletal muscle will split this bond releasing free energy and allowing for contraction Once the bond is broken and the free energy has been used you are left with an adenosine diphosphate molecule ADP and a free inorganic phosphate molecule Pi The ADP and Pi will then be processed in one of many metabolic pathways to reform ATP using free energy derived from food There are also two more bonds that can be used to release free energy however they are typically not used because they store less free energy that the 1st bond and the result in the formation of molecules AMP or Adenosine that cannot be readily metabolized back into ATP Given these two physiologic facts further reduction of the ADP molecule is not a favorable process and thus rarely occurs 1st and 2nd laws of thermodynamics definition The thermodynamic laws govern energy flow in biological systems The first law states that energy is never created or destroyed merely changes forms An example of this is the digestion of food in the GI tract and subsequent metabolism in skeletal muscle to form ATP The energy in the food has been transferred to ATP but no energy has been created or destroyed The second law states that all physical processes lead to an increase in entropy Another name for entropy is disorder In the case of humans this law is used to describe metabolic efficiency Metabolic efficiency is a measure that describes how much of the energy in a given food in converted to ATP Humans like most warm blooded mammals are relatively inefficient There are also two more bonds that can be used to release free energy however they are typically not used because they store less free energy that the 1stbond and the result in the formation of molecules AMP or Adenosine that cannot be readily metabolized back into ATP Given these two physiologic facts further reduction of the ADP molecule is not a favorable process and thus rarely occurs Lecture 1 Bioenergetics For each energy system know substrate products rate limiting or important enzymes and what inhibits activates them exercise duration examples physical location of the energy system in the cell ATP PC System Reactants and products This simple pathway involves donation of a Pi from PCr to ADP to form ATP Unlike limited freely available ATP in the cell energy released by the breakdown of PCr is not directly used for cellular work Instead it regenerates ATP to maintain a relatively constant supply under resting conditions Reactants PCr and ADP Products ATP and Creatine Rate limiting enzyme The release of energy from PCr is catalyzed by the enzyme creatine kinase which acts on PCr to separate Pi from creatine The energy released can then be used to add a Pi molecule to an ADP molecule forming ATP As energy is released from ATP by the splitting of a phosphate group cells can prevent ATP depletion by breaking down PCr providing energy and Pi to re form ATP from ADP Following the principle of negative feedback and rate limiting enzymes discussed earlier creatine kinase activity is enhanced when concentrations of ADP or Pi increase and is inhibited when ATP concentrations increase Inhibition activation of enzyme When intense exercise is initiated the small amount of available ATP in muscle cells is broken down for immediate energy yielding ADP and Pi The increased ADP concentration enhances creatine kinase activity and PCr is catabolized to form additional ATP As exercise progresses and additional ATP is generated by the other two energy systems the glycolytic and oxidative systems creatine kinase activity is inhibited Exercise examples duration The ATP PC System works very rapidly and is used for activities great quick bursts of energy like sprinting 40 yard dash powerlifting shot put etc The duration for this is less than 3 seconds in the book it says 5 15 seconds Location in the cell In the cytosol Glycolysis Reactants and products Glucose 2 ATP 2 Lactate H2O 2 phases energy investment energy production Rate limiting enzyme The rate limiting enzyme in the glycolytic pathway is phosphofructokinase or PFK Like almost all rate limiting enzymes PFK catalyzes an early step in the pathway the conversion of fructose 6phosphate to fructose 1 6 diphosphate Increasing ADP and Pi concentrations enhance PFK activity and therefore speed up glycolysis while elevated ATP concentrations slow glycolysis by inhibiting PFK Additionally because the glycolytic pathway feeds into the Krebs cycle for additional energy production when oxygen is present products of the Krebs cycle especially citrate and hydrogen ions likewise feed back to inhibit PFK Know how many ATP NAD NADH are used produced in each phase Energy Investment Phase In this first phase of glycolysis glucose a 6 carbon