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Transcript
Human Anatomy & Physiology 4/29/2017 05C.6 ATP & ATP Regeneration ATP! ATP! Cell energy is great for me! What happens if a muscle cell is lacking ATP or the components to make more ATP? …they let us know by cramping, burning, fatigue, and sometimes ‘aching’ us into helping them No ATP….no power stroke…fatigue or lack of contraction! No ATP….the myosin head cannot release….cramp A. ATP…what is it anyway? ATP is the molecule that is known as ‘cell energy’. The cell uses this molecule to do work… ATP = real name…Adenosine Triphosphate Adenosine is the base molecule that three phosphates are going to attach to. Now….this is easier said than done because these phosphates have a negative charge and really are not fond of being next to one another. First part of the molecule begins as A + P- = AMP (Adenosine Monophosphate) This molecule does not have a great amount of energy, because it did not take a lot of energy to bond one phosphate to adenosine. Second part of the molecule continues as another phosphate is added to AMP. Now, this is going to require more energy for this to happen because both phosphates are negative. A + P- ~ P- = ADP (Adenosine Diphosphate) Notice how the symbol ~ is used to show that a high-energy bond was used to get these two phosphates together. ADP has more energy stored than AMP because it took more energy to make this molecule. 05C.6 ATP & ATP Regeneration 1 of 7 Third part of the molecule finishes by adding another phosphate bond to the group. This is going to take some work, because two negatives want to repel the next negative phosphate group to be added. Because of this obstacle, the MOST ENERGY will be used to get the third phosphate group on! A + P- ~ P- ~ P- = ATP or ADP ~ P- = ATP The third phosphate bond contains the MOST ENERGY of the bonds! *When a muscle uses ATP, it only releases the third phosphate…because it has the most energy! *Muscles do not want to release all the phosphates and have to start all over…so it only releases the phosphate that has the most energy! Also, it easier and faster for the cell to regenerate ATP starting with ADP instead of AMP! ATP example (can & snake) B. Three way to get ATP Regeneration 1. Creatine Phosphate (CP): This is a quick and easy way to turn ADP into ATP! Creatine Phosphate is found in the cytoplasm. It will easily give up its phosphate to ADP! CP + ADP = ATP + Creatine (Which is now a waste product, will be discarded by the cell and filtered out by the kidney’s into the urine.) This quick and easy way to regenerate ADP into ATP does not require O2 (oxygen) and is considered anaerobic. Some sport supplements exploit this regeneration by providing a higher dosage of creatine. The idea is to load the muscles with more CP and increase the muscle’s ability to convert ADP into ATP at a greater rate. Some athletes report having increased muscle stamina using this type of product. (Which begs the thought that too much of a good thing can become a bad thing…especially for the kidneys who have to clean out all the extra creatine.) 05C.6 ATP & ATP Regeneration 2 of 7 2. Glycolysis Break glycolysis down into glycol = glucose; lysis = to break apart and we have the concept of this cycle: BREAK GLUCOSE APART! Why would we break it apart? “To get a little bit of energy, but more importantly, glucose is too big to get into the mitochondria.” Glycolysis cycle: The process of splitting glucose occurs outside of the mitochondria in the cytoplasm and requires no oxygen (anaerobic). Leave ~ 5 lines & room on the right side for the rest of this diagram. Think of NAD as a taxi or carrier for Hydrogen. Aka “acceptor” NAD only has ‘one seat’ for hydrogen. When carbons are split or pulled off a molecule, these taxis or acceptors can pick up hydrogens. Notice: that only enough energy was created to make 4 ATP’s, but it takes 2 ATP’s to split glucose. The net gain out of glycolysis is 2 ATP’s. Also note that 2 NADH were formed. The pyruvic acid is still too big to go into the mitochondria. It will now need to loose one more carbon before it will be small enough to go in through the mitochondria’s membrane. 05C.6 ATP & ATP Regeneration 3 of 7 Pyruvic acid (C3) will loose a carbon, which will be picked up and removed by oxygen to become CO2 and hydrogen (NADH). The new C2 molecule is Acetyl CoA and can easily go through the membrane and fall into the Citric Acid Cycle also known as the Kreb’s cycle. Notice that oxygen (O2) is a carbon acceptor after glycolysis is finished and is the beginning of the aerobic breakdown of Pyruvic acid. WHAT HAPPENS IF NO OXYGEN IS AVAILABLE? a Remember that oxygen HAS TO BE AVAILBALE for Pyruvic acid to loose a carbon. After about 15-20 seconds of activity (depending on how ‘in shape’ the person is), oxygen is depleted and is no longer there to accept the carbon. What does Pyruvic acid do if no oxygen is around? It gives up! It becomes a nasty molecule of Lactic Acid! Lactic acid is a ‘dead end’ molecule for muscles. Because no oxygen is available and the citric acid cycle isn’t being fed acetic acid, every thing comes to a halt and ATP diminishes and the muscle fatigues and can even cramp. The build up of lactic acid gives the muscle a ‘burning’ feeling. Some athletes use the term ‘feel the burn’ to know that they are pushing the endurance of the muscle metabolism to its limit. Lactic acid has a bad rap, because it has a positive purpose to protect the muscles from working to a point of damage. Also, pushing a muscle into fatigue only causes the muscle to adapt by chemically stimulating more blood vessels to grow (increase O2 delivery) and mitochondrial division to increase the number of mitochondria (match needed ATP formation to match the workload being demanded of the muscles). The ability of the muscle to adapt to increased energy demands and workloads is known as conditioning or ‘getting into shape’. 5 3. Citric Acid Cycle (Kreb’s cycle) The purpose of this cycle is to GRAB HYDROGENS! This cycle goes through a process of taking carbons off molecules, which need oxygen to pick them up…making this cycle AEROBIC! 05C.6 ATP & ATP Regeneration 4 of 7 As we know, when a carbon is pulled off, hydrogens come with it. So…the ‘oneseater taxi’ NAD will be there to grab up hydrogens along with another taxi that can carry two hydrogens. This taxi or acceptor is known as FAD. Remember that one glucose molecule made two Pyruvic acid molecules, so the cycle below is doubled. Citric Acid Cycle (Kreb’s) Leave ~ 10 lines below this diagram for the rest. Notice: the citric acid cycle only makes 2 ATP’s (count it twice for both pyruvic acids and we get a whopping 4 ATP’s!). Not a whole lot of ATP for this cycle to make, but remember that the main purpose of this cycle is to GET THOSE HYDROGENS! with each turn of the cycle, 6 NADH’s and 2 FADH2’s are created! (This is a total of two pyruvic acids.) that oxygen must be present for the cycle to continue. Oxygen is not used to create ATP, but instead is needed as a Carbon acceptor = CO2. Again…the main objective here is to pull carbons to get hydrogens! What to do with ALL THOSE HYDROGENS? Why are they SO IMPORTANT? 05C.6 ATP & ATP Regeneration 5 of 7 Let’s keep this simple. Notice the cristae of the mitochondria (it is how they recognize this organelle). With in the cristae, hyrdrogens will have their electrons taken from them. The electrons will be taken (pumped) to a higher gradient and then dropped down to a lower gradient, where the hydrogens should be ‘hanging out’ so they can get their electron back. When the electrons are dropped, they release energy! This energy is used to regenerate ADP back into ATP! Electron Transport Chain Leave ~ 8 lines below this diagram for the rest. Notice: that the electron ‘falls’ and releases energy that is transferred into bonding a third phosphate onto ADP. (ADP ~ P- = ATP) that the hydrogen, now with a positive charge (H+), gather at the end of the gradient in order to get their electron back. oxygen then picks up the hydrogens, that are no longer needed here, and forms H2O. The ETC is an AEROBIC cycle. Here, oxygen is a hydrogen acceptor and forms water as a ‘waste product’. In the ETC, NADH from the Citric Acid Cycle will generate enough energy to regenerate 3 ADP’s into 3 ATP’s and 05C.6 ATP & ATP Regeneration 6 of 7 FADH2 will generate energy to regenerate 2 ADP’s into 2 ATP’s. NADH = 3 ATP FADH2 = 2 ATP Let’s count our ATP production: *2 NADH from Glycolysis x 2 ATP = 2 NADH from Pyruvic Acid to Acetyl CoA 6 NADH from Citric Acid Cycle_________ 8 NADH x 3 ATP = 2 FADH2 x 2 ATP = Total for the ETC: 4 ATP 24 ATP 4 ATP 32 ATP 95 % of ATP production comes from the Aerobic part of glucose metabolism (CitricAcid Cycle and ETC)! If we add in the 2 ATP from Glycolysis and the 2 ATP from the Citric Acid Cycle to our 32 ATP’s , we get a total of 36 ATP from one glucose molecule. *(These NADH molecule had to be ‘escorted’ into the mitochondria, so they will only generate 2 ATP’s) The ability of a person to raise their aerobic pathways to meet workload can lead athletes to use this means of ATP regeneration for hours of physical activity. Reduce, Recite, Reflect, & Review! 05C.6 ATP & ATP Regeneration 7 of 7