Laura Spenceley Task 1 – Energy Systems Tom Cross

ATP

ATP is a nucleotide which contains a large amount of chemical energy stored in its high energy phosphate bonds. It releases energy when it is broken down into ADP. The energy is used for many metabolic processes. ATP is produced by cellular respiration in the mitochondria and by photosynthesis in the chloroplasts. ATP is regenerated by the Krebs Cycle. The by-products of this cycle are Carbon Dioxide, ATP, FADH and NADH.

Aerobic Energy System

The aerobic energy system uses fats, carbohydrates and sometimes proteins to resynthesize ATP. The aerobic energy system produces far more ATP than other energy systems however it produces ATP at a much slower rate so cannot produce ATP at the rate needed to fuel intense exercise.

The aerobic energy system is comprised of 3 main stages;

1. AEROBIC GLYCOLYSIS Purpose – to break down glucose to form 2 pyruvates. Where – glycolysis takes place in the cytoplasm and requires no oxygen.

Stages of aerobic glycolysis:

Glycolysis – the process of the breakdown of 6-carbon glucose into two 3-carbon pyruvic acid units.

The hydrogen ions removed join with the hydrogen carrier NAD to form NADH2. Whilst some energy is needed to begin glycolysis there is an overall net gain of 2 ATP. The pyruvic acid (3C) enters the matrix of the mitochondrion where it is oxidized (i.e. 2H

removed) and a carbon dioxide is lost. This process forms a two carbon molecule called acetyl-CoA (2C).

The hydrogen ions which have been removed join with NAD to form NADH2.

Laura Spenceley Task 1 – Energy Systems Tom Cross

2. THE KREBS CYCLE Purpose - to produce energy carrier molecules such as NADH. Where – takes place in the mitochondria and requires oxygen.

Stages of The Krebs Cycle: Acetyl-coenzyme A enters the Krebs cycle. Acetyl-Coenzyme A is broken down into carbon

dioxide (a waste product which is expelled through breathing) and hydrogen.

2 more ATP are synthesised during this process and made available to fuel further muscle contractions.

Hydrogen is transferred to the electron transport chain.

3. ELECTRON TRANSPORT CHAIN (ETC) Purpose – Produces 34 molecules of ATP for every 1 glucose molecule Where -

Hydrogen ions from Krebs cycle are carried to the electron transport chain by carrier molecules.

Hydrogen ions are transferred to carrier molecules embedded in the electron transport chain where they go through a series of chemical reactions.

A hydrogen ion gradient is created. As hydrogen ions move across this gradient another form of ATPase phosphorylates ADP (adds another phosphate group) to form ATP.

Water is created as a by-product as hydrogen combines with oxygen.

Laura Spenceley Task 1 – Energy Systems Tom Cross

Aerobic metabolism fuels the majority of the energy needed for long endurance activity. It utilises oxygen to convert nutrients to ATP. This system is slower than the anaerobic systems because it relies on the circulatory system to transport oxygen to the operating muscles before it creates ATP. The aerobic metabolism is used primarily during high endurance exercise, which is usually less intense and can continue for long periods of time.

During exercise an athlete will move through these metabolic pathways. As exercise begins, ATP is produced via anaerobic metabolism. With an increase in breathing and heart rate, there is more oxygen available and the aerobic metabolism begins and continues until the lactate threshold is reached. If this level is surpassed, the body cannot deliver oxygen quickly enough to generate ATP and anaerobic metabolism kicks in again. Since this system is short-lived and lactic acid levels rise, the intensity cannot be sustained and the athlete will need to decrease intensity to remove lactic acid build-up. This can be shown when comparing long distance running and short sprints. Whilst exercising aerobically, such as long distance running, an athlete’s energy requirements remain at a steady state throughout therefore they can run continuously at this steady rate, as soon as they begin to run at a quicker pace their energy requirements change and they begin to work anaerobically.

Spencer and Gastin tested highly trained males who were specialists in one of the distances (200m, 400m, 800m and 1500m) which were to be tested for their investigation. Their aim was to find the overall contribution from the aerobic and anaerobic energy systems for different length of distance run. It was expected that the shorter, more intense runs would have a higher

anaerobic contribution than the longer, less intense runs which had a higher aerobic

contribution. As expected the results from their investigation showed that the shortest duration/distance event relatively required the least amount of aerobic contribution whilst the longest duration/distance event relatively required the highest amount of aerobic contribution.

Laura Spenceley Task 1 – Energy Systems Tom Cross

LACTIC ENERGY SYSTEM

As shown above in the Aerobic Energy System when we exercise, the body converts glycogen in to ATP which is used to provide energy for the muscles to contract with the support of oxygen. Once those stores are depleted, the body resorts to an alternate source of energy; anaerobic energy systems.

The lactic energy system is sometimes known as Anaerobic Glycolysis due to the initial process being the same as aerobic glycolysis only without oxygen. As before 10 chemical reactions occur within the sarcoplasm which turns Carbohydrate into Pyruvic acid and 2 molecules of ATP. The difference now being the lack of oxygen meaning the carrier molecule NAD+ cannot offload the Hydrogen (H+) by-product of glycolysis causing a build-up in the cell. To try to prevent an increase in acidity the pyruvic acid accepts the H+, forming Lactic acid. If oxygen was present the H+ would be transported to the Mitochondria for use in the Kreb's cycle. Lactic acid is thought to interfere with muscle contraction due to disrupting the binding of Calcium to Troponin. Acidity also stimulates free nerve endings within the muscle, causing pain. Due to lactic acid production, this energy system can only be predominant for up to 2 minutes.

Following anaerobic exercise, despite the metabolic process used not requiring oxygen, your body will be in an Oxygen debt meaning respiration rate will be very high. The liver is responsible for clearing up the lactic acid build up that develops. Your body produces lactic acid as a safety precaution

when you remain in a constant anaerobic state to prevent muscle contractile failure. The

diagram left shows the process in which the liver prevents lactic acid build up to avoid any long

term issues with a build-up of lactic acid.

http://thefitnessgrail.wordpress.com/2012/04/01/lactic-acid-training-for-fat-loss/ANAEROBIC ENERGY SYSTEM

The Anaerobic energy system is also known as the Phosphocreatine energy system. The system

Laura Spenceley Task 1 – Energy Systems Tom Cross

utilises Creatine phosphate to create ATP. ATP is a high-energy compound which is stored in regulated quantities within the muscle. The high energy phosphate bond in Creatine Phosphate is broken down to release energy and is immediately used to recreate ATP. The anaerobic energy system acts as a reinforcement system for ATP as it helps regenerate ATP from ADP immediately. The Creatine Phosphate stores within the muscles are extremely limited whilst providing enough energy for 5 – 12 seconds of work at maximum intensity. Once this process has been completed the Creatine Phosphate will then need to be regenerated. Other useful fuels such as fat and glycogen are required to supply energy for the effective regeneration of ATP.

The anaerobic energy system is used in sports which require explosive movements as it is able to provide an instant rush of activity lasting a few seconds. Sports which will use this energy system effectively may be;

100m Sprints Javelin Long Jump High Jump Weight lifting

So in conclusion, the type of sport you do depends on the energy system used to provide you the energy to carry out the activity to the level you are working at. Below are a few examples of the type of sport and the energy system that would be used for that specific sport:

Anaerobic – Sprinter 100m

Lactic – 400m Swimmer

Aerobic- Marathon Runne