energy systems Flashcards
What is ATP?
- Adenosine triphosphate is a nucleotide derivative and consists of ribose, adenine and three phosphate groups.
- ATP is an immediate source of energy and is more desirable to use than glucose as ATP can be broken down in a single step to release a manageable quantity of energy.
- ATP is not stored in large quantities as it can easily be reformed from ADP in seconds.
- ATP is used in a variety of different ways, these include, metabolic processes, movement, active transport, secretion and activation of molecules.
- In sport, ATP is vital for muscle contractions to be performed as ATP is stored in muscle
How ATP releases energy
- Energy is released when ATP is hydrolysed to form ADP and a phosphate molecule.
- This process is catalysed by ATP hydrolase.
- The energy comes from the phosphodiester bonds between the phosphate molecules.
- These phosphodiester bonds are very unstable and thus have a low activation energy.
- The breaking of these is quick and releases a considerable amount of energy.
ADP + PI
- There is only enough ATP to last around 6 secs so body needs to recreate ATP from the ADP+Pi
- Condensation of ADP and inorganic phosphate catalysed by ATP synthase produces ATP during photosynthesis and respiration.
- The 3rd phosphate is joined by the bond being re-synthesised
3 ways for ATP being resynthesized from ADP+Pi
- there are 3 ways for this to occur depending on the duration/ intensity of exercise, fuel source and availability of oxygen
- These energy systems include:
1. the ATP-PC (alactic) pathway
2. Lactate pathway
3. Aerobic pathway
The ATP-PC system key features
- Type: anaerobic
- Fuel Source: Creatine Phosphate (PC)
- Duration: Approx. 6-10 seconds worth of energy
- Recovery Time: About 3 mins
- Used in: Sports requiring explosive power
how the ATP-PC system can resynthesize ATP
- As ATP only lasts 6 seconds, after this ATP needs resynthesizing as it is currently ADP (ADP has 2 phopshates, ATP has 3- therefore needs to have another phosphate join ADP to form ATP)
- Creatine phosphate is present in muscle cell (PC)
- Creatine phosphate is hydrolysed to provide the energy required (creatine phosphate bond is broken so creatine and phosphate split and the phosphate from PC joins onto ADP to resynthesise ATP)
- 1 PC molecule can produce (resynthesize) 1 new ATP molecule (1:1)
+ and - of ATP-PC system
+ PC is already stored in muscle alongside ATP so is readily available to be used
+ no oxygen is required, so system can get going quickly
+ very simple reaction means energy production can occur very quickly
+ no negative by-products
-similar to ATP, there isn’t very much PC in the muscles to sustain the system for longer than 10 seconds. Therefore only good for power/sprinting events
The lactate system key features
> The purpose of the system is to use glycogen/glucose to restore ATP in the muscle cells to be used (known as glycolysis).
- like the ATP-PC pathway, the lactate pathway is anaerobic. No oxygen is required.
- Type: anaerobic Glycolysis
- Fuel source: Glycogen
- Duration: Approx. 10 secs to 1-3 mins
- Recovery time: 1-2 hours
- Used in: stop/start games, field and court sports
how the lactate system can resynthesize ATP
- As ATP-PC system only lasts around 10 seconds, after this ATP still needs resynthesizing
- Glucose is present in the bloodstream, glycogen is present in the muscle cells and liver (it is the stored version of glucose)
- phosphorylating glucose to glucose phosphate (use 2x ATP molecules, both hydrolysed to produce 2x phosphate which is added to glucose. Energy released)
- Triose phosphate produced (high energy glucose phosphate molecule splits to form 2x triose phosphates)
- Oxidation of TP to produce pyruvate (both TP oxidised as NAD picks up H from the TP = NADH. Therefore, NAD is reduced, TP is oxidised, to form pyruvate.
- Oxidation of TP to pyruvate releases 2x ATP.
- Overall, 2x pyruvate produced with net gain of 2x ATP and 2x NADH. These are actively transported from cytoplasm to mitochondrial matrix.
- 1 glycogen molecule produces (resynthesizes) 3 new ATP molecules (1:3)
As there is pyruvate produced but since there is no oxygen available to put it to use, pyruvate is converted to lactate in bloodstream. This is done by the 2x pyruvate being reduced (gains the H from NADH produced in glycolysis). This oxidation of NAD ensures it can be reused in glycolysis and ensure more ATP can be produced without O2. The process cannot occur for a long time however as lactic acid will denature the coenzyme NAD
+ and - of lactic system
+ no oxygen required so doesn’t need to supply O2, quicker
+ produces greater yield of ATP (1:3)
+ lasts longer than ATP-PC system (few mins)
- only lasts a few mins
- lactate produced, 25x the resting level of muscle acidity after just 2 mins of intense activity. This increase of acidity = can inhibit breakdown of glycogen so glycolysis may stop and limit availability of further ATP, enzymes may denature, and may interfere with muscular contraction (heavy, weak)
The aerobic system key features
- Type: Aerobic Glycolysis (& Lipolysis)
- Fuel Source: Glycogen and fat
- Duration: Longer than 2 mins
- Recovery time: 24-48 hours
- Used in: Long distance and endurance events
how the aerobic system can resynthesize ATP
- As the lactate system only provides energy for 2 mins max, ATP still needs to be resynthesized (glycolysis already occurred)
- The product pyruvate from glycolysis does not turn into lactic acid this time as oxygen is available.
- LINK REACTION: the pyruvate is oxidised to acetate (as NAD is reduced by picking up H from pyruvate to form NADH) and at the same time Co2 is produced. Acetate combines with Coenzyme A to produce acetyl-coenzyme A. This process occurs 2x for every glucose, as 2x pyruvate was produced in glycolysis. Therefore, the products include: 2x Acetyl-coenzyme A, 2x Co2, 2x reduced NAD.
↳ OR- Acetyl-coenzyme A can be created by fats by beta- oxidation (breakdown of fatty acids) - KREBS CYCLE: acetyl-coenzyme A reacts with a 4 carbon molecule, releasing coenzyme A (it can be reused in previous steps) and producing a 6 carbon molecule to enter cycle. This 6 carbon molecule loses electrons (oxidised) being picked up by coenzymes that are reduced (3x NAD= 3x NADH & FAD= FADH). ADP+Pi also produces ATP, and 2x Co2 is released. This then leaves a 4 carbon molecule once more. Again, the process has to occur 2x, so products include: 6x NADH, 2x FADH, 2x ATP and 4x Co2 is lost
- OXIDATIVE PHOSPHORYLATION (ETC): we currently have 10x NADH (2x from glycolysis, 2x from link and 6x from kerbs) and 2x FADH from 1 glucose molecule. The electrons from these coenzymes (H) passed down ETC. When electrons move to next protein, releases energy to transport proton to intermembrane space by active transport (ATP). Causes an electrochemical gradient. Protons use ATP synthase to facilitated diffuse across phospholipid bilayer, this catalyses reaction of ADP+Pi = ATP (phosphorylation of ATP). At the end of the ETC, O2 can pick up electrons and protons (H) from ATP synthase, creating water.
- In the whole process, 3 key by-products include CO2, O2 and H2O. The ATP helps muscular contractions. 1 glycogen molecule produces around 34 new ATP molecules (1:34)
+ and - of aerobic system
+ produce energy for long time due to large store of glycogen and fat
+ can use fat as fuel so don’t have to use glycogen, so glycogen stores last longer, so not as tired
+ yield is a lot larger (1:34)
+ no harmful waste products (O2, H2O and CO2) easily removed
- very complex system so takes a while to get going, quite slow supply of sufficient O2, can lead to O2 deficit.
The energy continuum
- at any given time, all 3 energy systems are in use.
- however not all contribute the same amount of energy, as sometimes a certain system is favoured over another, due to the intensity and demand for energy
e.g. if it is high intensity, large majority of ATP from the ATP-PC system/lactate (anaerobic) and if it is lower intensity, larger proportion of aerobic system used. - on graph: as intensity is high, natural ATP produced from muscles, then ATP-PC takes over, then anaerobic glycolysis (lactate), then aerobic glycolysis (then aerobic lipolysis).
- however, all stores are working, just when the previous store decreases ATP, the next store increases ATP. So as one store declines on graph, the next will start to rise higher. But they all work continuously throughout. The systems overlap.
- overall, the aerobic systems last much longer.
Energy contributions in sport
- there are different energy contributions for different phases of play
- as intensity changes, the energy demand can be met with different energy systems
- e.g. more intense = anaerobic
- when the aerobic system is providing most of the energy, other systems replenish, so can use again if intensity increases.
