Why don't active muscle cells export pyruvate?
953717
This is an interesting question. I'm not too familiar with gluconeogenesis but I can tell you why lactate is sent to liver cells and not pyruvate:\n\nThe process of glycolysis requires NAD+ to function. During glycolysis, NAD+ strips away electrons from glucose (forming NADH) in order to break it down into pyruvate. Glycolysis therefore needs a constant supply of NAD+.\n\nNow, the process of lactic fermentation is not important because pyruvate is converted to lactate. It is important because during the process, the NADH is converted back to NAD+. This NAD+ is needed to keep glycolysis going. This is why the cells go a step further to convert the pyruvates into lactates.
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glycolysis-occur in the cytoplasm\nelectron transport chain-occur in the mitochondria\nkrebs cycle-occur in the mitochondria.\nif you consider mitochondria as part of the cytoplasm then all of the above..\nbut if not then it will be (a)
335741
This is basic biochemistry.  All cells (really, all bacteria, all fungi, all plants, all animals) use glucose or other simple sugars as a main source of fuel for energy generation.  (Some will argue that plants actually produce glucose, they both produce and consume it).  The process of glucose breakdown is glycolysis, and it generates energy in the form of ATP, and converts molecules such as NADH to NAD+.  This electron loss gets passed through the electron transport chain  in the mitocondria to generate more ATP.  \n\nCarbohydrates include complex and simple sugars.  Simple sugars can be broken down directly in cells, there are specific receptors that bring in the sugar.  Complex carbs such sucrose (a disaccryide, or a molecule containing two simple sugars) just contain more than one simple sugar in a chain.  They are broken down in the gut by specific enzymes that break the chain and release simple sugars.  Starch is a form of a carbohydrate, but not digestable to mammals, because we lack the enzyme to break it down.  Some bacteria don't though, and they live inside the gut of some mammals such as cows, and when cows eat grass, the starch is broken down by the bacteria and some of it is released into the gut.  So thats why mammalian herbavours exist.  \n\nFat metabolism.  Fats are long carbon chain connected at one end, usually three are connected to glycerol, this is called a triglyceride, and is a perferred form of storage.  Fats are broken down by chopping the carbon chain and generating energy.  Fat burning is slow and fat is a backup fuel source; the primary being simple sugars. \n\nProtein metabolism.  Proteins are digested by proteases in the gut, and the free amino acids are absorbed into the blood stream, where they can enter cells.  Cells can utilize amino acids for energy, but it's not that efficient.  Instead cells utilized amino acids for building new proteins; including the 'essential' amino acids, those that can't be generated by mammalian cells (we lack the enzymes).  So some amino acids are absolutely critical for our well-being.  \n\nLow carb diets simply don't have much carbs, and force the body to switch to fat to burn (in theory).  In reality it doesn't work too well.  During initial exercise, muscles use glycogen, a stored form of glucose, for energy. Also fat is utilized, and a bit of protein.  After 2 hours of exercise (or so, depending on the person), muscle glycogen is depleted, and body must use fat and glucose and protein.  If you do not intake glucose during this exertion, your performance will rapidly drop off; you can only burn so much fat at a time.  So the best advice for fat burning is exercise (at 60-70% max heart rate) for an hour or two, 3, 4x a week, and keep hydrated with water or gatoraid.  \n\nHigh carb diets make it easier for long term exercise by increasing the amount of muscle glycogen.
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1.  C - Lactic Acid and ATP\n\n2.  B - Oxygen\n\n3.  Because when a human muscle needs energy, it uses stored energy (ATP) first. After that, there is an oxygen debt in the muscles so the muscles have to figure out a way to get energy without oxygen.  That would be lactic acid fermentation.  Lactic acid fermentation does produce energy for the muscle to use, but also produces a byproduct called lactic acid that causes the burning sensation we feel in our muscles.  After exercising, heavy breathing is required to "repay" the oxygen debt that the muscle has created.\n\n4.  The acidity of the salt prevents bacteria from breaking down the meat.\n\n5. The mitochodria provide the energy needed for the centrioles to pull the sister chromatids apart during mitosis and meiosis.  They are evenly spread after the seperation because both new cells would need the mitochodria for energy as well.
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released from muscle stores as a form of energy
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AEROBIC AND ANAEROBIC RESPIRATION:\nRespiration is a chemical process, occurring in the mitochondria in the cytoplasm of all living cells, which breaks down sugar to provide energy for the cell\n\n-Aerobic respiration requires the presence of oxygen \n-Anaerobic respiration does not require oxygen \n-Glucose is a source of energy in the cell \n-The chemical that transports and transfers energy in the cell is called ATP (adenosine triphosphate). \nD-uring respiration sugar is broken down into CO2 and water \n-During Respiration the energy compund ATP is made from ADP and inorganic phosphate molecules (Pi) \n-ADP + Pi + energy from respiration  ATP \n-Where energy is required within the cell the reverse reaction takes place \n-ATP  ADP + Pi + energy· \n-Some heat is lost as waste during respiration. \n+Stages of respiration:         \n\nGlycolysis· \n-requires glucose as an energy source \n-Broken down aerobically into pyruvic acid \n-The pyruvic acid is broken down aerobically or anaerobically \n-two molecules of ATP are generated in this stage.         \nAerobic Breakdown\n-Only happens in the presence of oxygen: \n-Pyruvic acid enters the aerobic respiration system \n-CO2 is generated as waste \n-Hydrogen is given energy \n-It is passed on to a hydrogen acceptor molecule \n-It is then called a reduced hydrogen acceptor \n-Hydrogen is passed into another chemical system \n-The waste hydrogen is reacted with the oxygen to make water \n-The energy from the hydrogen is used to turn 36 molecules of ADP into 36 molecules of ATP \n-Giving a total of 38 molecules of ATP for aerobic respiration \n  \nAnaerobic Breakdown\n-In the absence of oxygen pyruvic acid is changed to: \nLactic acid in mammals \n-Alcohol (ethanol) and carbon dioxide in plants and fungi (such as yeast) \n-No further energy is produced \n-Giving a total of 2 molecules of ATP for anaerobic respiration. \n-Lactic acid in muscles leads to fatigue: \n-The reaction in animals is reversible – once oxygen is available the lactic acid is converted back to pyruvic acid. \n-The reaction in plants leading to alcohol is not reversible.
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Organelles don't have much of an effect on cell function--mostly it's its shape. More active cells are smaller than less active cells so information can quickly pass through the cytoplasm and into the nucleus. This explains why muscle cells are long, small and slender, and fat cells are large and bulky. \n\nThe membrane of smaller cells has many exterior folds to increase its surface area and ablitily to collect nutrients necessary for cell function.
427818
Absolutely not. In shock, your tissues are not getting as much oxygen and nutrients as they require. Nothing is happening metabolically to the glucose (sugar) in your blood. Your cells, on the other hand, may be unable to get enough oxygen, and thus may turn the glucose they do have into a waste product called lactate rather than into something that is further usable metabolically (called pyruvate). A buildup of lactate can pose a serious threat, as it can result in acidosis. For more information, check out the Wikipedia article I have referenced below.\n\nAs a side note, that lactate I mentioned is what we humans make when we do not get enough oxygen. However, if you were a yeast, you would indeed make ethanol (the type of alcohol we drink) in the absence of oxygen.
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There is a popular misconception that muscles are 'broken down' by the lactic acid that builds up during exercise, but this isn't quite true.  Lactate will indeed build up to high levels in the muscle, but not lactic acid.  The reason why acidosis may occur in muscles after strenuous exercise (leading to fatigue and then later soreness) is because of the protons that build up when ATP is hydrolysed.  This will cause some damage to the muscle fibrils (within the muscle cell), and when they recover they will be replaced with greater numbers.  Note, there is no increase in the amount of muscle cells, the muscle cells just get bigger.
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B.  C4 plants have a unique molecule into which CO2 is incorporated.  Then the unique molecule will release the CO2 when it is trasported to it neighbor cell.
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when we move our muscles,the energy comes directly from the glucose stores in the muscle itself by what is called aerobic respiration,which is the burning of glucose in the presence of oxygen,but after sometime of use the muscle needs more energy and the available oxygen wont be enough to make the aerobic respiration,so it shifts towards the anaerobic to produce energy and this type produces lactic acid,which accumulates in the muscle and causes it to spasm.\nusually muscle spasm resolves within 2 or 3 days,and using hot packs or massage with mild exercise will help.
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After glycolysis is finished 2 molecules of acetic acid are "loaded" into Kreb's on the enzyme Acetyl Co-A.  Co-A then returns to glycolysis in the cytoplasm to get more acetic acid.\n\nMean time the acetic acid adds to oxaloacetice acid (A 4 carbon structure) and gives a 6 carbon structure called citric acid. (2+4=6).\n\nThen CO2 and NADH2 is formed and we drop down to a 5 carbon structure called alpha ketgluteric acid and then lose CO2 and NADH2.  We also have created enough energy at this point to form an ATP and a low energy "hydrogen bus" FADH2.\n\nWhich brings us back to the 4 carbon structure oxaloaceitic acid, and we start all over again. \n\nThe purpose of Kreb's is to load what I call hydrogen busses (NADH2) because they are what unload electrons in the electron transport system which gives us a huge amount of ATP's (34).\n\nHope this helps.
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Aerobic respiration requires oxygen in order to generate energy. It is the preferred method of pyruvate breakdown from glycolysis and requires that pyruvate enter the mitochondrion to be fully oxidized by the Krebs cycle. The product of this process is energy in the form of ATP (Adenosine Triphosphate), by substrate-level phosphorylation, NADH and FADH2. The reducing potential of NADH and FADH2 is converted to more ATP via an electron transport chain with oxygen as the "terminal electron acceptor". Most of the ATP produced by cellular respiration is by oxidative phosphorylation, ATP molecules are made due to the chemiosmotic potential driving ATP synthase. Respiration is the process by which cells obtain energy when oxygen is present in the cell.\n\nTheoretically, 36 ATP molecules can be made per glucose during cellular respiration, however, such conditions are generally not realized due to such losses as the cost of moving pyruvate into mitochondria. Aerobic metabolism is rather more efficient than anaerobic metabolism. They share the initial pathway of glycolysis but aerobic metabolism continues with the Krebs cycle and oxidative phosphorylation. The post glycolytic reactions take place in the mitochondria in eukaryotic cells, and at the cell membrane in prokaryotic cells.\n\nGlycolysis\nMain article: Glycolysis \nGlycolysis is a metabolic pathway that is found in all living organisms and does not require oxygen. The process converts one molecule of glucose into two molecules of pyruvate, and makes energy in the form of two net molecules of ATP. Four molecules of ATP per glucose are actually produced but two are consumed for the preparatory phase. The initial phosphorylation of glucose is required to destablise the molecule for cleavage into two triose sugars. During the pay-off phase of glycolysis four phosphate groups are transfered to ADP by substrate-level phosphorylation to make four ATP and two NADH are produced when the triose sugars are oxidised. Glycolysis takes place in the cytoplasm of the cell. The overall reaction can be expressed this way:\n\nGlucose + 2 ATP + 2 NAD+ + 2 Pi + 4 ADP → 2 pyruvate + 2 ADP + 2 NADH + 4 ATP + 2 H2O + 4 H+ \n\nOxidative decarboxylation\nMain article: Oxidative decarboxylation \nProduces acetyl-CoA from pyruvate. This oxidation reaction also releases carbon dioxide as a product.\n\nKrebs cycle/Citric Acid cycle\nMain article: Citric acid cycle \nWhen oxygen is present, acetyl-CoA enters the citric acid cycle, and gets oxidised to CO2 while at the same time reducing NAD to NADH. NADH can be used by the electron transport chain to create further ATP as part of oxidative phosphorylation. To fully oxidise the equivalent of one glucose molecule two acetyl-CoA must be metabolised by the Krebs cycle. Two waste products, H2O and CO2 are created during this cycle, .\n\nOxidative phosphorylation\nMain articles: Oxidative phosphorylation , Electron transport chain , Electrochemical gradient, and ATP synthase\n\nIn eukaryotes, oxidative phosphorylation occurs in the mitochondria. It comprises of the electron transport chain that establishes a proton gradient (chemiosmotic potential) across the inner membrane by oxidising the NADH produced from the Krebs cycle. ATP is synthesised by the ATP synthase enzyme when the chemiosmotic gradient is used to drive the phosphorylation of ADP.\n\nTheoretical yields\nThe yields in the table below are for one glucose and molecule being fully oxidised to carbon dioxide. It is assumed that all the reduced coenzymes are oxidised by the electron transport chain and used for oxidative phosphorylation.
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No. I think you misheard the statement that you never gain or lose muscle cells, they only change in size.
516806
I can't tell if you are asking about tranport across the plasma membrane or mitochondrial membrane.  Both lactate and pyruvate transport out of the cell (through the plasma membrane) is increased in acidic conditions.
189578
I could copy the answer, but I have some good links instead. \nSkeletal muscle fibers are multinucleated and fusiform, and basically contain myofibrills. See details at the link:\nhttp://training.seer.cancer.gov/module_anatomy/unit4_2_muscle_structure.html\n\nPay special attention to the myofibrils, the mitochondria and the sarcoplasmic reticulum :-)\n\nIllustrations of structure at different levels (I wish these pictures had been around years ago when I studied this!):\nhttp://www.agen.ufl.edu/~chyn/age2062/lect/lect_19/179.gif\nhttp://www.mhhe.com/biosci/esp/2001_gbio/folder_structure/an/m5/s5/assets/images/anm5s5_1.jpg
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option e is correct\nBerkeley -- In the lore of marathoners and extreme athletes, lactic acid is poison, a waste product that builds up in the muscles and leads to muscle fatigue, reduced performance and pain. \n\nSome 30 years of research at the University of California, Berkeley, however, tells a different story: Lactic acid can be your friend. \n\nCoaches and athletes don't realize it, says exercise physiologist George Brooks, UC Berkeley professor of integrative biology, but endurance training teaches the body to efficiently use lactic acid as a source of fuel on par with the carbohydrates stored in muscle tissue and the sugar in blood. Efficient use of lactic acid, or lactate, not only prevents lactate build-up, but ekes out more energy from the body's fuel. \n\nIn a paper in press for the American Journal of Physiology - Endocrinology and Metabolism, published online in January, Brooks and colleagues Takeshi Hashimoto and Rajaa Hussien in UC Berkeley's Exercise Physiology Laboratory add one of the last puzzle pieces to the lactate story and also link for the first time two metabolic cycles - oxygen-based aerobic metabolism and oxygen-free anaerobic metabolism - previously thought distinct. \n\n"This is a fundamental change in how people think about metabolism," Brooks said. "This shows us how lactate is the link between oxidative and glycolytic, or anaerobic, metabolism." \n\nHe and his UC Berkeley colleagues found that muscle cells use carbohydrates anaerobically for energy, producing lactate as a byproduct, but then burn the lactate with oxygen to create far more energy. The first process, called the glycolytic pathway, dominates during normal exertion, and the lactate seeps out of the muscle cells into the blood to be used elsewhere. During intense exercise, however, the second ramps up to oxidatively remove the rapidly accumulating lactate and create more energy. \n\nTraining helps people get rid of the lactic acid before it can build to the point where it causes muscle fatigue, and at the cellular level, Brooks said, training means growing the mitochondria in muscle cells. The mitochondria - often called the powerhouse of the cell - is where lactate is burned for energy. \n\n"The world's best athletes stay competitive by interval training," Brooks said, referring to repeated short, but intense, bouts of exercise. "The intense exercise generates big lactate loads, and the body adapts by building up mitochondria to clear lactic acid quickly. If you use it up, it doesn't accumulate." \n\nTo move, muscles need energy in the form of ATP, adenosine triphosphate. Most people think glucose, a sugar, supplies this energy, but during intense exercise, it's too little and too slow as an energy source, forcing muscles to rely on glycogen, a carbohydrate stored inside muscle cells. For both fuels, the basic chemical reactions producing ATP and generating lactate comprise the glycolytic pathway, often called anaerobic metabolism because no oxygen is needed. This pathway was thought to be separate from the oxygen-based oxidative pathway, sometimes called aerobic metabolism, used to burn lactate and other fuels in the body's tissues. \n\nExperiments with dead frogs in the 1920s seemed to show that lactate build-up eventually causes muscles to stop working. But Brooks in the 1980s and '90s showed that in living, breathing animals, the lactate moves out of muscle cells into the blood and travels to various organs, including the liver, where it is burned with oxygen to make ATP. The heart even prefers lactate as a fuel, Brooks found. \n\nBrooks always suspected, however, that the muscle cell itself could reuse lactate, and in experiments over the past 10 years he found evidence that lactate is burned inside the mitochondria, an interconnected network of tubes, like a plumbing system, that reaches throughout the cell cytoplasm. \n\nIn 1999, for example, he showed t