Cellular respiration is, in its broadest definition, the process in which the chemical bonds of energy-rich molecules such as glucose are converted into energy usable for life processes. Oxidation of organic material—in a bonfire, for example—is an exothermic reaction that releases a large amount of energy rather quickly. The overall equation for the oxidation of glucose is: :::C6H12O6 + 6O2 → 6CO2 + 6H2O + energy In cellular respiration, this oxidation process is broken down into two basic metabolic pathways: glycolysis, anaerobic respiration or aerobic respiration. ==Glycolysis== ''Main article: Glycolysis'' Glycolysis 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 molecules of Adenosine triphosphate. Glycolysis takes place in the cytoplasm of the cell (biology). The overall reaction can be expressed this way: :Glucose + 2 NAD+ + 2 ATP + 2 Pi → 2 NADH + 2 pyruvate + 4 ATP + 2 H2O + 4 H+ The individual steps of the conversion of glucose into pyruvate are (in brief): #A glucose molecule from the hydrolysation of starch or glycogen is phosphorylated using one ATP molecule to give glucose-6-phosphate. #The glucose-6-phosphate is converted to fructose-6-phosphate by isomerisation. #Fructose-6-phosphate is again phosphorylated to give fructose-1,6-diphosphate with the use of another ATP molecule. #Next, the fructose-1,6-diphosphate is then lysed into two molecules of 3-carbon sugar (dihydroxyacetone phosphate and glyceraldehyde-3-phosphate) which are interconvertible. #The 3-carbon sugars are dehydrogenated and inorganic phosphate is added to them, forming two molecules of 1,3 diphosphoglycerate. #The hydrogen is used to oxidise two molecules of NAD, a hydrogen carrier, to give NADH+H+. NADH+H+ later proceeds to the mitochondria for use in the electron transport chain. #The two molecules of 1,3 diphosphoglycerate lose two phosphate groups to form two molecules of glycerate-3-phosphate (3-phosphoglycerate), converting two molecules of ADP to ATP. #The two molecules of glycerate-3-phosphate again lose phosphate forming two molecules of pyruvate, with the production of another two ATP molecules (for a net gain of 2 ATP). ==Breakdown of pyruvate== There are now two ways to break down the resulting pyruvate: ===Aerobic respiration (Cellular Respiration)=== ''Aerobic respiration'' requires oxygen in order to generate energy. It is the preferred method of pyruvate breakdown. A molecule of pyruvate acid travels into a mitochondrion entering the citric acid cycle. In this process it is broken down producing energy in the form of ATP (which travels to the cell), NADH and FADH2 which travel to the electron transport chain. In this process, an electron is transferred from an energy-rich atom (such as a carbon atom in an organic molecule) to an oxygen atom, via an electron transport chain. Oxygen serves as the "terminal electron acceptor" in the electron transport chain. In the process, it yields 36 ATP molecules via the diffusion of hydrogen atoms through an ATP synthase, as well as carbon dioxide and water. This makes for a total gain of 38 ATP molecules during cellular respiration under optimal conditions; however, such conditions are generally not realized due to such losses as the cost of moving pyruvate into mitochondria. This takes place in the mitochondria in eukaryotes, and at the cell membrane in prokaryotes. Aerobic metabolism is rather more efficient than anaerobic metabolism. It actually starts off with the Glycolysis process of anaerobic metabolism, and then continues with the krebs cycle and oxydative phosphorylation. ====Glycolysis==== Usually whatever is being metabolised is first converted to Acetyl-CoA, for sugars this would be by sugar->pyruvate by glycolysis then pyruvate->Acetyl-CoA. This process yields a net gain in energy in the form of Adenosine_triphosphate. If no oxygen is present, then the proces goes no further. (see also: anaerobic metabolism ) The word equation for aerobic respiration is glucose+oxygen=carbon dioxide+water+energy ====Krebs cycle==== When oxygen is present, Acetyl-CoA enters the citric acid cycle, and gets converted to CO2 while at the same time converting NAD + H to NADH. NADH can be used by several different processes to create further Adenosine triphosphate. Commonly Oxidative phosphorylation in the mitochondria, where oxygen is used to split the H off of NADH, and to produce further ATP in the process. ===Anaerobic respiration (Fermentation)=== "Anaerobic respiration" It does not require oxygen. True anaerobic respiration involves an electron acceptor other than oxygen. Bacteria are capable of using a wide variety of compounds as terminal electron acceptors in respiration: nitrogenous compounds (such as nitrates and nitrites), sulfur compounds (such as sulfates, sulfites, sulfur dioxide, and elemental sulfur), carbon dioxide, iron compounds, manganese compounds, cobalt compounds, and uranium compounds. However, none of these alternative electron acceptors yields as much energy from respiration as does oxygen. In environments where oxygen is present, typically only aerobic respiration will occur. Fermentation is a process in which pyruvate is partially broken down, but there is no Krebs cycle and no production of ATP by an electron transport chain. Fermentations of various kinds produce a number of different compounds. Textbook examples of fermentation products are ethanol (drinkable alcohol), lactic acid, and hydrogen. However, more exotic compounds can be produced by fermentation, such as butyric acid and acetone. Although fermentation produces no ATP, it is useful to the cell because it regenerates nicotinamide adenine dinucleotide (NAD+), which is consumed by glycolysis. * Ethanol fermentation (done by yeast and some types of bacterium) breaks the pyruvate down into ethanol, carbon dioxide, and water. It is important in bread making, brewing, and wine making. * Lactic acid fermentation breaks the pyruvate down into lactic acid, carbon dioxide, and water. It occurs in the muscles of animals when they need energy faster than the blood can supply oxygen. It also occurs in some bacteria. It is this type of bacteria that convert lactose into lactic acid in yogurt giving it its sour taste. Fermentation products contain chemical energy that cannot be further broken down by fermentation, making fermentation less efficient than respiration. Fermentation releases a total of two ATP molecules per molecule of glucose (compare to the approximately 38 of aerobic respiration). == See also == * Citric acid cycle * Carbohydrate catabolism == External links == * [http://www.people.virginia.edu/~rjh9u/glycol.html A detailed diagram of glycolysis] * [http://departments.oxy.edu/biology/bio130/lectures_2000/metabolic_products.htm Chart of Important Metabolic Products] Cellular respiration Metabolism
== Original author's note == This page's content comes from what I've learned in high school biology. Some of it may be incorrect. Also, I'm guessing that there's just a ''little'' more that could be added. By all means, do so (of course, that's what the 'pedia is all about). --User:Bdesham == Table / flow chart == I've added a basic diagram covering the subprocesses of aerobic respiration.I've done it as a table rather than uploading the whole thing as a .png so that others can easily modify the info. However looking at the edit page the table looks complicated and offputting. If anyone wants to amend the content of the diagram but is put off editing the table by all the ugly HTML by all means let me know on my talk page and I will edit the table for you. User:Theresa knott 13:56 6 Jun 2003 (UTC) :Yeah, that table is kinda offputting. I've made a flow chart in PNG format; if anyone needs/wants to change it, visit User Talk:Bdesham and say so. --User:Bdesham 19:43 9 Jun 2003 (UTC) == Incorrect number of ATP? == I wasn't going to say anything, since my knowledge is limited to high school bio, but when I see this page was also made with that knowledge...we were taught a net gain of 36 ATP, not 38...perhaps you forgot to subtract the 2 used in glycolysis? EDIT: In fact, the glycolysis article agrees with me--kreb's and the ETC makes 34 ATP/glucose. User:24.218.58.113 19:39, 26 Nov 2004 (UTC). Further edit: the previous was me, I am a new user. After referencing my biology textbook, the real answer (I believe) is that 38 ATP is the *optimal* gain, generally not realized due to such losses as the energy needed to move pyruvate into the mitochondria. I will make a minor edit to reflect this; please correct me if this is the wrong action. User:Endersdouble 19:47, 26 Nov 2004 (UTC) : Hmm... looking back at my notes from HS Biology, they say that the total gain of ATP from glycolysis ''and'' aerobic respiration is 38 (2 from glycolysis and 36 from aerobic respiration). I googled for "cellular respiration", though, and I found [http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/CellularRespiration.html]. If you look under the "How many ATPs?" section, it says that the theoretical total is 38, but that due to conditions the number rarely exceeds 30. I'll look into this more when I have time. Cheers! --User:Bdesham 19:49, 26 Nov 2004 (UTC) This is how it work: In vitro (in a test tube with every ezymers, substrates at the right conditions), a biochemist can make 38 molecues of ATP from a molecule of glucose. However, in a eucaryotic cell, Glycolysis (which produces ATP and NADH)occurs in the cytoplasm while respiration (and the recycling of NADH) occurs inside the mitochomdria. And this is the problem: -- All the NAD in the cytoplasm would become NADH and glycolysis will stop due the the lack of NAD; Therefore, NADH in the cytoplasm must be transported into the mitochondria to unload its protons and electons (i.e NADH--> NAD). This transporting cost 2 ATP; thereforem in eucaryotes, we said they produce 36 ATP. However, these type of calculation is meaningless-- If all glucose are committed to produce ATP and CO2, all living organisms will be the same- pails of ATP! The fact is, a cell will not produce a single molecue of ATP more than it need.
Cellular respiration is, in its broadest definition, the process in which the chemical bonds of energy-rich molecules such as glucose are converted into energy usable for life processes. Biochemistry Cell biology Respiration Metabolism
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Words begining with Cellular_respiration:
Cellular_respiration
Cellular_respiration
Cellular_respiration
Cellular respiration
Cellular respiration is, in its broadest definition, the process in which the chemical bonds of energy-rich molecules such as glucose are converted into energy usable for life processes. Oxidation of organic material—in a bonfire, for example—is an exothermic reaction that releases a large amount of energy rather quickly. The overall equation for the oxidation of glucose is: :::C6H12O6 + 6O2 → 6CO2 + 6H2O + energy In cellular respiration, this oxidation process is broken down into two basic metabolic pathways: glycolysis, anaerobic respiration or aerobic respiration. ==Glycolysis== ''Main article: Glycolysis'' Glycolysis 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 molecules of Adenosine triphosphate. Glycolysis takes place in the cytoplasm of the cell (biology). The overall reaction can be expressed this way: :Glucose + 2 NAD+ + 2 ATP + 2 Pi → 2 NADH + 2 pyruvate + 4 ATP + 2 H2O + 4 H+ The individual steps of the conversion of glucose into pyruvate are (in brief): #A glucose molecule from the hydrolysation of starch or glycogen is phosphorylated using one ATP molecule to give glucose-6-phosphate. #The glucose-6-phosphate is converted to fructose-6-phosphate by isomerisation. #Fructose-6-phosphate is again phosphorylated to give fructose-1,6-diphosphate with the use of another ATP molecule. #Next, the fructose-1,6-diphosphate is then lysed into two molecules of 3-carbon sugar (dihydroxyacetone phosphate and glyceraldehyde-3-phosphate) which are interconvertible. #The 3-carbon sugars are dehydrogenated and inorganic phosphate is added to them, forming two molecules of 1,3 diphosphoglycerate. #The hydrogen is used to oxidise two molecules of NAD, a hydrogen carrier, to give NADH+H+. NADH+H+ later proceeds to the mitochondria for use in the electron transport chain. #The two molecules of 1,3 diphosphoglycerate lose two phosphate groups to form two molecules of glycerate-3-phosphate (3-phosphoglycerate), converting two molecules of ADP to ATP. #The two molecules of glycerate-3-phosphate again lose phosphate forming two molecules of pyruvate, with the production of another two ATP molecules (for a net gain of 2 ATP). ==Breakdown of pyruvate== There are now two ways to break down the resulting pyruvate: ===Aerobic respiration (Cellular Respiration)=== ''Aerobic respiration'' requires oxygen in order to generate energy. It is the preferred method of pyruvate breakdown. A molecule of pyruvate acid travels into a mitochondrion entering the citric acid cycle. In this process it is broken down producing energy in the form of ATP (which travels to the cell), NADH and FADH2 which travel to the electron transport chain. In this process, an electron is transferred from an energy-rich atom (such as a carbon atom in an organic molecule) to an oxygen atom, via an electron transport chain. Oxygen serves as the "terminal electron acceptor" in the electron transport chain. In the process, it yields 36 ATP molecules via the diffusion of hydrogen atoms through an ATP synthase, as well as carbon dioxide and water. This makes for a total gain of 38 ATP molecules during cellular respiration under optimal conditions; however, such conditions are generally not realized due to such losses as the cost of moving pyruvate into mitochondria. This takes place in the mitochondria in eukaryotes, and at the cell membrane in prokaryotes. Aerobic metabolism is rather more efficient than anaerobic metabolism. It actually starts off with the Glycolysis process of anaerobic metabolism, and then continues with the krebs cycle and oxydative phosphorylation. ====Glycolysis==== Usually whatever is being metabolised is first converted to Acetyl-CoA, for sugars this would be by sugar->pyruvate by glycolysis then pyruvate->Acetyl-CoA. This process yields a net gain in energy in the form of Adenosine_triphosphate. If no oxygen is present, then the proces goes no further. (see also: anaerobic metabolism ) The word equation for aerobic respiration is glucose+oxygen=carbon dioxide+water+energy ====Krebs cycle==== When oxygen is present, Acetyl-CoA enters the citric acid cycle, and gets converted to CO2 while at the same time converting NAD + H to NADH. NADH can be used by several different processes to create further Adenosine triphosphate. Commonly Oxidative phosphorylation in the mitochondria, where oxygen is used to split the H off of NADH, and to produce further ATP in the process. ===Anaerobic respiration (Fermentation)=== "Anaerobic respiration" It does not require oxygen. True anaerobic respiration involves an electron acceptor other than oxygen. Bacteria are capable of using a wide variety of compounds as terminal electron acceptors in respiration: nitrogenous compounds (such as nitrates and nitrites), sulfur compounds (such as sulfates, sulfites, sulfur dioxide, and elemental sulfur), carbon dioxide, iron compounds, manganese compounds, cobalt compounds, and uranium compounds. However, none of these alternative electron acceptors yields as much energy from respiration as does oxygen. In environments where oxygen is present, typically only aerobic respiration will occur. Fermentation is a process in which pyruvate is partially broken down, but there is no Krebs cycle and no production of ATP by an electron transport chain. Fermentations of various kinds produce a number of different compounds. Textbook examples of fermentation products are ethanol (drinkable alcohol), lactic acid, and hydrogen. However, more exotic compounds can be produced by fermentation, such as butyric acid and acetone. Although fermentation produces no ATP, it is useful to the cell because it regenerates nicotinamide adenine dinucleotide (NAD+), which is consumed by glycolysis. * Ethanol fermentation (done by yeast and some types of bacterium) breaks the pyruvate down into ethanol, carbon dioxide, and water. It is important in bread making, brewing, and wine making. * Lactic acid fermentation breaks the pyruvate down into lactic acid, carbon dioxide, and water. It occurs in the muscles of animals when they need energy faster than the blood can supply oxygen. It also occurs in some bacteria. It is this type of bacteria that convert lactose into lactic acid in yogurt giving it its sour taste. Fermentation products contain chemical energy that cannot be further broken down by fermentation, making fermentation less efficient than respiration. Fermentation releases a total of two ATP molecules per molecule of glucose (compare to the approximately 38 of aerobic respiration). == See also == * Citric acid cycle * Carbohydrate catabolism == External links == * [http://www.people.virginia.edu/~rjh9u/glycol.html A detailed diagram of glycolysis] * [http://departments.oxy.edu/biology/bio130/lectures_2000/metabolic_products.htm Chart of Important Metabolic Products] Cellular respiration Metabolism
Cellular respiration
== Original author's note == This page's content comes from what I've learned in high school biology. Some of it may be incorrect. Also, I'm guessing that there's just a ''little'' more that could be added. By all means, do so (of course, that's what the 'pedia is all about). --User:Bdesham == Table / flow chart == I've added a basic diagram covering the subprocesses of aerobic respiration.I've done it as a table rather than uploading the whole thing as a .png so that others can easily modify the info. However looking at the edit page the table looks complicated and offputting. If anyone wants to amend the content of the diagram but is put off editing the table by all the ugly HTML by all means let me know on my talk page and I will edit the table for you. User:Theresa knott 13:56 6 Jun 2003 (UTC) :Yeah, that table is kinda offputting. I've made a flow chart in PNG format; if anyone needs/wants to change it, visit User Talk:Bdesham and say so. --User:Bdesham 19:43 9 Jun 2003 (UTC) == Incorrect number of ATP? == I wasn't going to say anything, since my knowledge is limited to high school bio, but when I see this page was also made with that knowledge...we were taught a net gain of 36 ATP, not 38...perhaps you forgot to subtract the 2 used in glycolysis? EDIT: In fact, the glycolysis article agrees with me--kreb's and the ETC makes 34 ATP/glucose. User:24.218.58.113 19:39, 26 Nov 2004 (UTC). Further edit: the previous was me, I am a new user. After referencing my biology textbook, the real answer (I believe) is that 38 ATP is the *optimal* gain, generally not realized due to such losses as the energy needed to move pyruvate into the mitochondria. I will make a minor edit to reflect this; please correct me if this is the wrong action. User:Endersdouble 19:47, 26 Nov 2004 (UTC) : Hmm... looking back at my notes from HS Biology, they say that the total gain of ATP from glycolysis ''and'' aerobic respiration is 38 (2 from glycolysis and 36 from aerobic respiration). I googled for "cellular respiration", though, and I found [http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/CellularRespiration.html]. If you look under the "How many ATPs?" section, it says that the theoretical total is 38, but that due to conditions the number rarely exceeds 30. I'll look into this more when I have time. Cheers! --User:Bdesham 19:49, 26 Nov 2004 (UTC) This is how it work: In vitro (in a test tube with every ezymers, substrates at the right conditions), a biochemist can make 38 molecues of ATP from a molecule of glucose. However, in a eucaryotic cell, Glycolysis (which produces ATP and NADH)occurs in the cytoplasm while respiration (and the recycling of NADH) occurs inside the mitochomdria. And this is the problem: -- All the NAD in the cytoplasm would become NADH and glycolysis will stop due the the lack of NAD; Therefore, NADH in the cytoplasm must be transported into the mitochondria to unload its protons and electons (i.e NADH--> NAD). This transporting cost 2 ATP; thereforem in eucaryotes, we said they produce 36 ATP. However, these type of calculation is meaningless-- If all glucose are committed to produce ATP and CO2, all living organisms will be the same- pails of ATP! The fact is, a cell will not produce a single molecue of ATP more than it need.
Cellular respiration
Cellular respiration is, in its broadest definition, the process in which the chemical bonds of energy-rich molecules such as glucose are converted into energy usable for life processes. Biochemistry Cell biology Respiration Metabolism
See other meanings of words starting from letter:
C
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Cellular_respiration
Cellular_respiration
Cellular_respiration
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