Metabolism for Exercise

In this chapter we describe in detail the three basic energy systems ATP/PCR, Glycolytic, and Oxidative. We focus on ATP which is energy metabolism and the synthesis of the storage form of energy in the body.  When ADP and a phosphate ion rejoin, ATP is formed by the energy provided from our food macronutrients . We look at the different energy systems and the max capacity that could be used in a specific exercise or real-life setting.  We talk about the importance of what energy source to use because by generating power from fat breakdown you only yield half of what you achieve with carbs. This results in your maximum aerobic output decreasing significantly because your muscle glycogen is depleted. When metabolizing glucose (the most basic form of energy) you get 36 ATP. Protein is used as a potentially important energy substrate but should be the last used (typically only used in survival/ starvation mode). We also talk about different muscle fiber types and how we use these to better our specific exercise. We go into detail about bioenergetics and the difference between catabolism and metabolism. Metabolism is the process where the food and liquids we take in is converted into energy.Catabolism is when large molecules are broken down into simpler ones while releasing energy.

Introduction 

The human body provides energy for our daily activities through a process called metabolism. Metabolism is the process where the food and liquids we take in is converted into energy. During metabolism, the food is combined with oxygen for the body to release energy for various functions. Metabolism are bodily reactions that can either result in catabolism or anabolism. Catabolism is when large molecules are broken down into simpler ones while releasing energy. Anabolism is the storage or build up of simple molecules to form larger molecules which requires energy. The three energy systems within the human body are ATP-PCr, glycolysis and oxidative. ATP-PCr is anaerobic and it transfers energy from PCr to ATP through ADP. ATP and phosphocreatine are stored in cells that create high amounts of energy. This system lasts for 10-15 seconds and uses high intensity exercise for a short duration of exercise. Glycolysis is where glucose is broken down into a series of fermentation reactions. Glucose is broken down through a pathway that involves glycolytic enzymes. Glycolysis lasts up to 60-90 seconds and occurs just outside the mitochondria. The last energy system is Oxidative. This system is the main source of ATP at rest and occurs during low-intensity activities. Oxidative system is used after 90 seconds of exercise and lasts very long up to 90 minutes. Unlike the other 2 systems, Oxidative is aerobic and uses primarily fats to supply energy. These three energy systems are important, because they work together to produce a continuous supply of energy for exercise.

ATP–PCr System  

ATP-PCr is an anaerobic system, which means that this process does not require oxygen. During an intense muscular activity, like sprinting, ATP is maintained at a relatively constant level during the first few seconds. However, PCr declines steadily to prevent the depletion of ATP (PCr gets broken down). By the end of the sprint, ATP and PCr levels are very low and cannot provide the muscles with energy to contract and relax, causing exhaustion. From this we can conclude that the energy that we can obtain of ATP from PCr is limited, at around 3-15 seconds. ATP is the source of energy for almost all metabolic processes. Our cells contain adenosine triphosphate (ATP) and phosphocreatine(PCr). The ATP-PCr system is the simplest system that involves the donation of a Phosphate ion from PCr to ADP in order to form ATP.  Creatine kinase is an enzyme that catalyzes the energy released from PCr by acting on the PCr molecule to separate the phosphate ion from creatine. The energy released from the previous catalyzation can be used to add a phosphate ion to an ADP molecule, forming ATP.  ATP depletion can be prevented by breaking down PCr, which will provide energy and phosphate ions to reform ATP from ADP.  increasing concentrations of ADP or phosphate ions enhances creatine kinase activity; Increase of ATP concentrations inhibits creatine kinase activity.  

o  Intense exercise initiates, the ATP in muscle cells gets broken down for immediate energy, increasing ADP and phosphate ions concentration. The ADP concentration enhances creatine kinase activity which catabolizes PCr molecules to form additional ATP.  This system has a passive recovery. In just around 30 seconds, 50% of the PC is replenished, and, in around 7/8 minutes, 100% of the PC is replenished).