Because fast fibers use anaerobic metabolism to create fuel, they are much better at generating short bursts of strength or speed than slow muscles. However they get tired more quickly. Fast fibers generally produce the same amount of force per contraction as slow muscles, but they get their name because they are able to fire faster. Having more fast fibers can be an asset to a sprinter since she needs to quickly generate a lot of force. Olympic sprinters are supposed to have about 80 % fast fibers, while those who excel in marathons tend to have 80% slow fibers. Slow fibers are more continuous and are able to keep making ATP since they take oxygen more. They are smaller in diameter, red in color, they depend on oxidative phosphorylation for their ATP supply, they have better blood supply, they have more mitochondria, and more myoglobin.
HOW DOES ATP WORK IN THE BODY?
ATP is stored in chemical bonds and is released when the last phosphate is lost and ATP becomes ADP. It is used to do work in the cell by a reaction that removes one of the phosphate-oxygen groups, leaving ADP. When ATP converts to ADP, the ATP is spent. Then the ADP is usually immediately recycled in the mitochondria where it is recharged and comes out again as ATP. The total human body content of ATP is only about 50 grams, which must be constantly recycled everyday. The ultimate source of energy for constructing ATP is food. ATP is the carrier and regulation-storage unit of energy. The average daily intake of 2500 food calories translates into a turnover of a whopping 180 kilograms of ATP.
WHAT IS THE RELATIONSHIP BETWEEN GLUCOSE, NADH AND FADH2?
Glucose has the most energy and during cellular respiration, it is broken down. The energy that is in glucose is stored in many molecules of NADH and a few of FADH2. NADH is able to store more energy than FADH2. This is why it is more abundant electron carrier. Also NADH can be synthesized from scratch or from tryphtophan. FADH2 has accommodation for two hydrogens while NAD accepts one hydrogen molecule. In NAD, an electron pair one hydrogen are transferred, with a second hydrogen released into the medium. Electron transfer by FADH2 produces less ATP than by NADH.
SUMMARY:
This chapter discusses about how ATP is produced, and how cells work for the process. There are two types of muscle fibers, slow and fast. Slow fibers such as marathoners make ATP using oxygen, aerobically. Fast fibers, such as sprinters, make ATP without oxygen anaerobically. Energy is essential for life processes. Photosynthesis make glucose from CO2 and H2O and releases O2. Other organisms need O2 and energy and release CO2 and H2O. Animals perform cellular respiration and plants perform both photosynthesis and cellular respiration since they have mitochondria. Breathing is the key of cellular respiration. The equation of cellular respiration is; C6H12O6 + 6O2 --> 6CO2 + energy. This tells that the atoms of the starting molecules glucose and O2 regroup to form the products CO2 and H2O. In this exergonic process, the chemical energy of the bonds in glucose is transferred and stored (banked). Cellular respiration can produce up to 38 ATP molecules for each glucose molecule. During cellular respiration, carbon-hydrogen bonds of glucose get broken, and electrons will be transferred to oxygen. Dehydrogenase (enzymes) remove hydrogen from an organic molecules. They also use NAD+ to shuttle electrons. NADH will be formed by transferring electrons to NAD+.
There are 3 stages in order to produce ATP in cellular respiration.
1) Glycolysis: Begins respiration by breaking glucose, a six carbon molecule, into two molecules of a three-carbon compound called pyruvate. It occurs in cytoplasm.
2) The citric acid cycle: Breaks down pyruvate into carbon dioxide and supplies the third stage with electrons. It occurs in mitochondria.
3) Oxidative phosphorylation: Electrons are shuttled through the electron transport chain. ATP is generated through oxidative phosphorylation associated with chemiosmosis. It occurs in inner mitochondrion membrane.
In glycolysis, glucose will be cut in half to produce two molecules of pyruvate. Two NAD+ are reduced to two NADH. At the same time, two ATP are produced by substrate-level phosphorylation. The pyruvate formed in glycolysis is transported the mitochondria, where it is prepared for entry into the next level. With the help of CoA, the acetyl enters the citric acid cycle. Oxidative phosphorylation requires the involvement of electron transport and chemiosmosis and also adequate supply of oxygen. NADH and FADH2 are involved as well.
There are three different categories of cellular poisons that affect cellular respiration.
1) Blocking of the electron transport chain, such as cyanide and carbon monoxide.
2) Inhibiting ATP synthase, such as oligomycin
3) Production of the membrane leaky to hydrogen ions, such as dinitrophenol
Muscles are able to oxidize NADH through lactic acid fermentation. NADH is oxidized to NAD+ when pyruvate is reduced to lactate. Pyruvate is serving as an electron sink, a place to dispose of the electrons generated by oxidation reactions in glycolysis.
KEY TERMS:
-kilocalorie: the quantity of heat required to raise the temperature of 1 kilogram of water by 1C.
-redox reaction: the movement of electrons from one molecule to another. Oxidation-reduction reaction.
-chemiosmosis: process that the potential energy of this concentration gradient is used to make ATP
-substrate-level phosphorylation: process that an enzyme transfers a phosphate group from a substrate molecule to ADP, forming ATP
-fermentation: an anaerobic energy-generating process taking advantages of glycolysis, which is producing two ATP and reducing NAD+ to NADH
-yeasts: single-called fungi that not only can use respiration for energy but can ferment under anaerobic conditions
-dehydrogenase: an enzyme that is used in the process of oxidizing glucose
-intermediates: compounds that form between the initial reactant, glucose, and the final product, pyruvate
-obligate anaerobes: prokaryotes that live in stagnant ponds and deep in the soil.
-facultative anaerobe: process that is able to make ATP either by fermentation or by oxidative phosphorylation, depending on whether O2 is available.
Glycolysis produces 2 ATP molecules by substrate level phosphorylation. Also it makes 2 pyruvate. In energy investment phase, it starts with one molecule of glucose and hexopkinase breaks down the bonds. Then in this stage, dihydroxyacetone phosphate and G3P are produced, but isomerase converts them into two G3P. Next payoff phase, NADH is made and at the end, pyruvate will be made and 4 ATP produced at the same time. It happens in the cytoplasm.
In the citric acid cycle, reactants are acetyl CoA. ATP and NADH and FADH2 are produced. 2 molecules are created in net amount and 6 molecules of NADH and 2 molecules of FADH2 are produced as well. CO2, oxaloacetate, as if combines with acetyl in the first step. It occurs in the mitochondria.
In oxidative phosphorylation, NADH and FAOH2, which give away their electrons to the electron transport chain as reactants. The reactants of chemiosmosis are ADP and phosphate, which form ATP as the products. They produce water molecules in the electron transport chain. Oxygen and hydrogen are two important molecules as are the mulriprote, complexes in the energy transport chain. 32 to 34 molecules of ATP are produced while no new NADH or FADH2 are formed. It happens in the inner membrane of the mitochondria.
5 FACTS:
1) Although glucose is considered to be the source of sugar for respiration, carbohydrates, proteins, and fats are the actual three sources for generation of ATP
2) Glycolysis is the universal energy-harvesting process of living organisms
3) The statement "plants perform photosynthesis and animals perform cellular respiration." is wrong, because plants do perform cellular respiration with mitochondria as well.
4) There are three stages of producing ATP, glycolysis, the citric acid cycle, and oxidative phosphorylation.
5) The total number of ATP molecules per a glucose molecule produced are 32 to 34. This is about 40% of a glucose molecule potential energy.
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