Chapter 3: Cellular Respiration
What is the product of glycolysis?
- 2 pyruvate molecules
What are the stages of glucose oxidation?
1. glycolysis 2. intermediate stage 3. citric acid cycle 4. electron transport system
What are the energy-requiring steps for transport- ing molecules during cellular respiration that decrease the actual net ATP produced?
1. pyruvate from the cytosol into mitochondria 2. phosphate and ADP into mitochondria for its use in ATP synthesis 3. NADH produced during glycolysis into mitochondria for oxidative phos- phorylation in the electron transport system.
What is the net energy molecules produced in citric acid cyle?
- 1 ATP per acetyl CoA (2 ATP total) - 3 NADH per acetyl CoA (6 NADH total) - 1 FADH2 per acetyl CoA (2 FAHD2 total)
What is the net energy molecules produced in intermediate stage?
- 1 NADH per pyruvate (2 NADH total)
What is the net energy molecules produced in glycolysis?
- 2 ATP and 2 NADH
What is the product of the citric acid cycle?
- 2 CO2 per acetyl CoA
What are the substrates of citric acid cycle?
- Acetyl CoA (2 acetyl CoA from each glucose)
How many ATP is produced from FADH2inelectrontransportsystem?
- FADH2 does not have as much energy, so the electrons move from the second enzyme complex/H+ pump to the fourth enzyme complex/H+ pump. This moving of the enzyme across only 2 H+ pumps only generates enough energy to produce 2 ATP.
How many ATP is produced by NAHD in electron transport system?
- NADH has a lot of energy, so the electrons move from the first enzyme complex/H+ pump to the 4th enzyme complex/H+ pump. This moving of the enzyme across 3 H+ pumps generates enough energy to produce 3 ATP.
Does glycolysis require oxygen?
- No, it is anaerobic and aerobic
What is the difference between substrate level phosphorylation and oxidative phosphorylation?
- Substrate level phosphorylation is the process of forming ATP by the physical addition of a phosphate group to ADP to make ATP. This occurs during glycolysis and Citric Acid Cycle. This type of phosphorylation you have an ADP. In order to turn it into an ATP, a phosphate group is taken from an intermediate compound, referred to as a substrate, and given to the ADP. Substrate level phosphorylation directly phosphorylates ADP to ATP by using the energy from a coupled reaction. - Oxidative phosphorylation happens in Electron Transport System and is the phosphorylation of ADP to ATP is dependent on the oxidative reactions occurring in the mitochondria, During this process electrons are exchanged between molecules (oxidized), which creates a chemical gradient that allows for the production of ATP. It involves two coupled reactions that are considered to simultaneously occur. In the period of oxidative phosphorylation, the energy produced during the oxidative reaction is transferred to ADP to form ATP.
What is the citric acid cycle of cellular respiration?
- The citric acid cycle also occurs in a mitochondrion, requires oxygen, and completes the break- down of glucose. Two CO2 molecules are produced per turn of the cycle. Energy is transferred during this process to form 1 ATP, 3 NADH, and 1 FADH2. Remember, this reflects the energy transferred per each acetyl CoA entering the citric acid cycle. Two acetyl CoA molecules are produced from 1 glucose molecule. Thus, the citric acid cycle must occur twice—so a total of 2 ATP, 6 NADH, and 2 FADH2 are formed from the original glucose molecule.
What is pyruvate?
- The end product of glycolysis - what chemical changes are made to pyruvate depends on the availability of oxygen, if sufficent oxygen available then it enters the mitochondria to enter the next phase of cellular respiration. However, if insufficient amount of oxygen, pyruvate is converted to lactate and does not go through with cellular respiration
What is the intermediate stage of cellular respiration?
- The intermediate stage occurs ina mitochondrion and requires oxygen. It involves a multien- zyme complex that converts pyruvate to acetyl CoA and 1 CO2 molecule. Energy is transferred to form 1 NADH mol- ecule. Remember, 1 NADH molecule is formed per pyruvate entering the intermediate stage. Recall that 2 pyruvates are produced from 1 glucose molecule. Thus, the intermediate stage must occur twice—so a total of 2 NADH molecules are formed from the original glucose molecule.
How is protein used in cellular respiration?
- The point of entry of deaminated amino acids (amino acids with the amine group [-NH2] removed) is dependent upon the specific type of amino acids. Different amino acids enter the metabolic pathway at glycolysis, the intermediate stage, or the citric acid cycle.
Does the citric acid cycle require oxygen?
- Yes, it is aerobic
What is the product of intermediate stage?
- acetyl CoA and 1 CO2 per pyruvate(2 CO2)
How many enzymes are needed for complete oxidation of glucose?
- at least 20 dif enzymes located in cells cytosol and mitochondria
Where does glycolysis occur?
- cytosol
What is substrate level phosphorylation?
- direct method of synthesizing ATP; The enzyme-catalyzed formation of ATP by direct transfer of a phosphate group to ADP from an intermediate substrate in catabolism.
What is the structure of the mitochondria?
- double-membrane organelle - cristae= outer membrane and an inner membrane that has inward folds - outer compartment= fluid filled space btwn the membranes - matrix= innermost space
What are other fuel molecules that are oxidized in cellular respiration?
- fatty acids and amino acids
What is beta oxidation?
- fatty acids are changed to form acetyl CoA and enters the cell respiration metabolic pathway at citric acid cycle. And since they enter at this pathway in the mitochondria they can only be oxidized aerobically
What is glycolysis stage of cellular respiration?
- first stage of cellular respiration; occurs in the cytosol, does not require oxygen (glycolysis can occur in presence or absence of oxygen). Energy is transferred to form 2 ATP molecules (net) and 2 NADH molecules. If sufficient oxygen is available, the pyruvate formed enters a mitochondrion and is further metabolized in the intermediate stage and the citric acid cycle.There is a total of 4 ATP made but 2 are invested early on in glycolysis which leaves a net of 2 ATP molecules produced
What is the substrate in glycolysis?
- glucose
How do we calculate the specific number of ATP molecules produced?
- glycolysis= Produces 2 ATP and 2 NADH. We know each NADH makes 3 ATPin Electron Transport System, so the stage of glycolysis makes a total of 6 ATP + 2 ATP - intermediate stage= Produces 2 NADH, which each NADH makes 3 ATPin Electron Transport System, so this stage makes a total of 6 ATP - citric acid cycle= Produces 2 ATP, 6 NADH and 2 FADH2. We know each NADH makes 3 ATP and we know each FADH2 makes 2 ATPin Electron Transport System. So this stage produces a total of 18 ATP + 4 ATP + 2 ATP - A grand total of 38 ATP... However, due to the several energy requiring steps for transporting molecules during cellular respiration there is a decrease in ATP produced. Making it a total of 30 ATP
How is the citric acid cycle regulated?
- in the first step of citric acid cycle the enzyme citric synthetase is regulated by levels of NADH, ATP and pathway intermediates. - If low level of NADH, ATP and pathway intermediates then cellular energy demands are high. This results in increases activity of enzyme citrate synthetase and thus the citric acid cycle - If high levels of NADH, ATP and pathway intermediates, then cellular energy demands are low. This results in decreased activity of enzyme citrate synthetase and thus the citric acid cycle
What is oxidative phosphorylation?
- indirect method of synthesizing ATP; the energy is released to coenzymes which then transfer the energy to form ATP;The process of forming ATP is referred to as oxidative phosphorylation because it involves oxygen as the final electron acceptor, and ATP is formed from the phosphorylation of ADP. This process is distinguished from substrate-level phosphorylation, which forms ATP from energy directly released from a substrate, as occurs in specific steps of glycolysis
What is the electron transport system stage of cellular respiration?
- involves the transfer of electrons (energy) from the coenzymes NADH and FADH2 that are produced during the first three stages of cellular respiration. The energy released from these coenzymes is used to form ATP.
How does the lack of oxygen affect glycolysis stage?
- lactate is produced to regenerate NAD+ so glycolysis can continue - lack of O2 inhibits pyruvate from entering intermediate stage thus NADH will oxidize and transfer its electrons to pyruvate to form lactate and lactate will get converted to glucose in a process called glycogenolysis which occurs in the liver, thus glycolysis can occur again, moreover, oxidation of NADH converts it into NAD+
What is the steps of intermediate stage of cellular respiration?
- link btwn multistep process of glycolysis stage and multistep process of citric acid cycle stage 1. pyruvate dehydrogenase, a multienzyme complex, brings together pyruvate and a molecule of coenzyme A (CoA), that is already present within the matrix. 2. decarboxylation= this bringing together of pyruvate and coenzyme A results in the release of a carboxyl group (one carbon and 2 oxygen) from the pyruvate molecule as CO2. Energy is released during decarboxylation as 2 hydrogen atoms (2 electrons plus 2 hydrogen ions) are transferred to coenzyme NAD+ to form NADH + H+ as byproduct. The pyruvate is now turned to acetyl CoA and CO2.
What is the pathway for citric acid cycle?
- metabolic pathway
What is the pathway of glycolysis?
- metabolic pathway
Where does the intermediate stage occur?
- mitochondria
Where does the citric acid cycle occur?
- mitochondrial matrix
What is the pathway or complex of intermediate stage?
- multienzyme complex
What is cellular respiration?
- multistep metabolic pathway whereby organic molecules (ie. glucose, fatty acids, amino acids) are disassembled (broken down) in a controlled manner by a series of enzymes - during the disassembly, potential energy stored in the molecule's chemical bonds is released; the energy is then used to make new bonds between ADP and Pi (free phosphate) to form ATP
What is glucose oxidaton?
- occurs within cells and is a breakdown of glucose with the accompanying release of energy to synthesize ATP - if oxygen is available then glucose is completely broken down and carbon dioxide and water are formed
How does lack of oxygen affect the citric acid cycle?
- pathway inhibited by lack of oxygen
How does lack of oxygen affect the intermediate stage?
- pathway inhibited by lack of oxygen
What is the substrate of intermediate stage?
- pyruvate (2 pyruvate from each glucose)
Does the intermediate stage require oxygen?
- yes, aerobic
What happens if there is not enough oxygen available for cellular respiration?
1. Cellular respiration processes requiring oxygen (i.e., aerobic cellular respiration) decrease, including the activity of the electron transport chain. Electrons remain with the NADH and FADH2 molecules and NADH and FADH2 accumulate. This is accompanied by decreased levels of NAD+ and FAD. 2. The cell becomes increasingly dependent upon glycolysis, a metabolic pathway that requires NAD+ to continue. 3. Extended low-oxygen conditions would ultimately result in the complete shutdown of glycolysis within the cell because of the lack of NAD+. 4. NAD+ must be regenerated if glycolysis is to continue. - Two electrons and hydrogen are transferred from NADH to pyruvate, which is converted to lactate. This enzymatic reaction is catalyzed by lactate dehydrogenase
What are the steps of the electron transport system?
1. Delivery of electrons by NADH and FADH2= Reduced electron carriers (NADH and FADH2) from other steps of cellular respiration releases hydrogen (electron and hydrogen ion) and these released electrons are transferred to molecules near the beginning of the transport chain and are passed through the electron chain to O2 (the O2 you breath!), which serves as the final electron acceptor. In the process, the NADH and FADH2 turn back into NAD+ and FAD, which can be reused in other steps of cellular respiration. 2. As electrons are passed down the chain, they move from a higher to a lower energy level, releasing energy due to kinetic energy being produced from moving from higher to lower energy levels. Their kinetic energy is harnessed by H+ pumps to move H+ from the mitochondrial matrix into the inner membrane space. This pump of H+ from the matrix to inner membrane space, establishes an electrochemical gradient (H+ pumps are proteins that transport H+ from the matrix to the inner membrane space. This maintains a H+ gradient between the inner membrane space and the matrix, with more H+ in inner membrane space than in the matrix, making the inner membrane space more positively charged than the matrix) 3. Since there are more H+ pumped out of the matrix and into the outer compartment, H+ will naturally move down its concentration gradient. Due to the non permeable membrane of the inner mitochondrial membrane, enzyme ATP synthase will transport H+ across the membrane and into the matrix. 4. The kinetic energy released by the H+ moving from inner membrane space to the matrix is harnessed by ATP synthase to form a new bond between ADP and a free phosphate to create ATP.
What are the steps of glycolysis?
1. phosphate group os transferred from ATP to glucose making glucose 6 phosphate 2. glucose 6 phosphate is converted to its isomer called fructose 6 phosphate 3. phosphate group is transferred from ATP to fructose 6 phosphate creating fructose 1, 6 bisphosphate 4. fructose 1, 6 bisphosphate is split to form dihydroxyacetone phosphate and glyceraldehyde 3 phosphate 5. dihydroxyacetone phosphate is converted to glyceraldehyde 3 phosphate making 2 glyceraldehyde 3 phosphate. 6. a free phosphate is added to glyceraldehyde 3 phosphate. glyceraldehyde 3 phosphate is oxidized losing 2 hydrogen atoms which get transferred to coenzyme NAD+ to form coenzyme NAHD + H+. The addition of a phosphate turns glyceraldehyde 3 phosphate to bisphosphoglycerate. And bc there are 2 glyceraldehyde 3 phosphate the product is 2 bisphosphoglycerate. 7. bisphosphoglycerate donates a phosphate group to ADP to make ATP. The bisphosphoglycerate turns to 3 phosphoglycerate. And bc there are 2 bisphosphoglycerate it has a product of 2 3 phosphoglycerate 8. 3 phosphoglycerate is turned to its isomer 2 phosphoglycerate. Bc there are 2 3 phosphoglycerate it makes a product of 2 2 phosphoglycerate. 9. 2 phosphoglycerate loses a H2O molecule making phosphoenopyruvate. And bc there are 2 2 phosphoglycerate it makes 2 phosphoenopyruvate. 10. phosphoenopyruvate donates a phosphate group to ADP making ATP. The loss of phosphate group turns phosphoenopyruvate to pyruvate. And bc there are 2 phosphoenopyruvate it makes 2 pyruvates. https://www.khanacademy.org/science/biology/cellular-respiration-and-fermentation/glycolysis/a/glycolysis
What is the steps of the citric acid cycle of cellular respiration?
1. the first enzyme to combine an acetyl CoA molecule produced in the intermediate stage with a molecule of oxaloacetate to form citrate. 2. H2O is removed from citrate to form intermediate molecule called acontitate 3. H2O molecule is added to the acontitate to form isomer isocitrate 4. decarboxylation occurs= carboxyl group is released from isocitrate as CO2. Energy released from breakage, reduces coenzyme NAD+ to NADH + H+. Isocitrate turns to α-ketoglutarate. 5. decarboxylation occurs= coenzyme A reacts with α-ketoglutarate and a carboxyl group is removed from α-ketoglutarate as CO2. The energy released from the breakage turn coenzyme NAD+ to NADH + H+. α-ketoglutarate is turned to succinyl CoA due to the addition of coenzyme CoA. 6. the CoA enzyme of succinyl CoA is replaced with a phosphate group, which is then transferred to ADP to make ATP. The removal of CoA from succinyl makes succinate 7. succinate is oxidized= 2 hydrogen atoms are removed (2 hydrogen ions and 2 electrons) from succinate and transfers it to coenzyme FAD to form FADH2. The removal of 2 hydrogen atoms from succinate forms fumarate. 8. a H2O molecule us added to fumarate to form malate 9. malate is oxidized= removal of 2 hydrogen atoms (2 electrons and 2 hydrogen ions) from malate, which get transferred to NAD+ to form NADH + H+. The removal of 2 hydrogen atoms from malate makes oxalocetate. 10. repeat one more time
What are the characteristics of cellular respiration/glucoseoxidation?
1. these processes are exergonic (energy releasing) 2. the organic molecule that gives up its energy has done so by releasing high energy electrons, so the molecule is being oxidized 3. energy released is used to synthesize ATP, which is endergonic (energy requiring process) 4. oxygen is required for maximum ATP production
