Citric Acid Cycle - Lab Report Example

Exam V: Digestive and metabolism A: Ingestion is incorrect I mistook this for digestion. C: Is the correct answer as mastication is the breakdown of food into small pieces to increase their surface area for enzyme for enzyme activities and to prevent choking. 2. B: is incorrect as mass peristalsis occurs in the large intestines, it pushes the contents of the colon from one division to another and peristalsis follows only one direction from the mouth to the anus and not back and forth. C: is correct choice because in the segmentation circular muscles contract while longitudinal muscles relax at alternating sections, this results in mixing of the food: which allows digestive enzymes increase their activity. 3. 4. C: is incorrect because saliva found in the mouth lubricates food, the choices were confusing and all of them were correct and thus I had difficulties choosing the right answer. D: is the best choise as all the listed are functions of the oral cavity. 5. C: is an incorrect answer, I chose it because skeletal muscles are involved in movement and tongue rolling being a movement I chose it. A: is the correct choice intrinsic muscles, muscles are responsible for the tongue rolling, these muscles allow some people to make different shapes using their tongues. 6. A: glottis is incorrect, I chose it because it prevents food from entering the trachea and directs it to the esophagus and thus I assumed they share a common pathway. C: is the correct answer as the pharynx is the conducting zone for the respiratory system and also part of the digestive system thus it is a shared pathway for food. 7. B: is incorrect choice, I was not sure which answer is correct. C: is the correct chose vit B12 must be bound to intrinsic factor before it absorbed in the small intestines. 8. A: I chose stimulation of the gut motility because the enzyme is involved in the stimulation of the digestion of protein and fat and thus I thought this also affects gut motility. C: is the correct answer the enzyme is involved in the stimulation of gall bladder contraction and thus it causes increased production of bile juice. 9. D: is incorrect, although I chose it, I confused mastication with digestion. The oral cavity is responsible for breaking down the food into small particle and part of the starch digestion starts there. B: the small intestine is the correct answer the adaptation of the small intestine, starting from the large surface area created by its folds to the high number of digestive enzymes it contains makes the most of the digestion of food. 10. B: is incorrect I thought vitamins and minerals do not need to be digested hence I thought they are absorbed directly, which I was wrong. D: lipoproteins are the correct answer because they transport cholesterol among tissues and thus they do not need to be digested as they are in their simplest units and thus are directly absorbed. 11. C: is incorrect I chose as I had difficulties selecting the correct answer and the choices were very confusing. D: is the correct answer as all the nutrients have to be absorbed in the blood stream first before they are destined to any other place in the body system. No nutrient is absorbed in the lymph lacteals prior entering the blood. 12. 13. 14. 15. 16. 17. B: is incorrect choice, I chose it because, I misunderstood the question. A: is the correct choice because cellulose is broken down into glucose, fructose and galactose in the process of digestion. 18. C: is incorrect I confused the answers, vit C is water soluble and thus it makes the incorrect choice. A: is the correct choice as Vit: A, D, E, and K are fat soluble vitamins. 19. A: is incorrect the choices were very confusing it was hard to identify the correct one. C: is the correct choice, the Uvula is a vestigial structure and thus nothing would happen during deglutition even if it was impaired 20. C: is the correct answer, as chyme would not be neutralized; the function of secreting is to stimulate the pancreas to release bicarbonate to neutralize the food passing through the stomach. 21. B: is incorrect answer I the word hypertonic solution confused me, and that is why I happen to choose this answer. C: is the correct answer because the acid in the duodenum is responsible for the inhibition of gastric acid through a negative feedback mechanism. 22. A: is incorrect I chose this answer as I did not understand the question well. B: is the correct answer complex carbohydrates do not raise the blood sugar levels as much as small sugars. 23. D: is an incorrect answer, all the choices seemed wrong and were confusing. A: is the correct answer the structure of omega 3 fatty acids contains 3 double bonds 24. B: is incorrect answer I chose it because the upper limit of the recommended fat is the same (35%). A: is the correct answer as it is the documented recommended amount of lipids that is required in an adult diet. 25. A: 4 is incorrect as this is the amount generated from substrate level phosphorylation C: is the correct answer as only 36 ATP can be produced at maximum efficiency. 26. B: is incorrect I had difficulties remembering the correct answer at the time I was answering this question. A: is the correct answer the citric acid contributes only 2 ATP molecules. 27. B: is the incorrect answer as glycolysis is the first stage in cellular respiration, I confused and picked this answer as I did not understand the question. D: is the correct answer when the mitochondrion is inactive there will not be any electronic transfer nor will the citric acid cycle take place. 28. A: is incorrect answer I chose it because build up of ketones causes ketoacidosis and thus I thought acids was the answer. D: acetones is the compound that builds up and causes sweetness of breath, and is common in people with diabetes 29. B: is incorrect choice, I chose it because I thought that a person absorbs to maintain a constant level of glucose. C: is the correct answer the process of maintaining blood glucose commences at the post-absorptive state when already some of the blood glucose has been utilized by the body. 30. C: is incorrect, I chose this answer because parietal cells do produce acids, but they do not prevent protein digestion. D: is the correct answer as these cells secrete gastric acid and intrinsic factors and thus activate the digestive enzymes in the stomach. 31. A: I chose A because it is also a function of the gastric acid in the stomach. D: is the best answer as all the above choices are the reasons for the acidic state of the stomach. 32. A: is incorrect, I thought that buffers prevent the stomach lining from being digested. D: is the correct choice, the mucus secreted in the stomach prevents the walls of the stomach from being digested. 33. 34. A: is incorrect because its not the best choise, I chose it because the pancreas too secretes the insulin hormone. C: is the best choise as the pancreas secretes both insulin and glucagon. 35. B: is the incorrect answer at chose it because I thought that chymotrypsin digests chime and thus neutralizes it. D: is the correct choise as the bicarbonate is alkaline and when secreted by the pancreas it neutralizes the chyme and prevents it from destroying the duodenal wall. 36. 37. C: I chose antibody recycling because it is one of the functions of the liver. A: is the correct the liver is involved with purification of blood, in this way toxic materials are removed from the body. 38. A: I chose this answer because bile aids in the digestion of fats, B: is the correct answer as the function of the bile juice is to emulsify fats. 39. A: I chose this answer because I thought that at first when the lipids are emulsified they can easily travel in the blood. B: is the correct answer as lipids are packed as lipoproteins so that they can travel easily in the bloodstream. 40. C: is incorrect choice, I chose lactic acid because it accumulates, then there is no oxygen in the tissues during the process of respiration. D: is the correct choise the vital molecule that would lack is acetyl-coA and thus the citric acid cycle would not take place. Essay: Citric Acid Cycle During glycolysis one molecule of glucose is converted to produce a net total of two pyruvate, two NADH, and two ATP. In anaerobic conditions, glycolysis is the only pathway for ATP production. NAP+ has to be regenerated to continue making ATP. In aerobic conditions, molecules of pyruvate and fatty acids are actively transported across the inner mitochondrial membrane and into the mitochondrial matrix where the pyruvate undergoes oxidation. Pyruvate oxidation takes place within the matrix of the mitochondria. Oxygen and two pyruvate go into pyruvate oxidation. The pyruvate goes from three carbons to two carbon acetyl. As a result, CO2 is released as waste. In the next step, NAD+ is reduced to NADH. Lastly, the pyruvate dehydrogenase complex attaches the CoA to the acetyl. No ATP is produced during pyruvate oxidation. During this entire process, two NADH’s are used for energy and the net products include two acetyl-CoA and two NADH. These two acetyl-CoA molecules become oxidized by the citric acid cycle. Acetyl-CoA can also be produced by breaking down fats and amino acids. Fatty acid oxidation occurs in the matrix, when a fatty acid is linked to the thiol group of coenzyme A. The acetyl CoA is removed from the fatty acid chain during each round and is fed into the citric acid cycle. This leads to the disassembly of the fatty acyl CoA molecule. Fatty acid oxidation produces one NADH and one FADH2. Once acetyl Co-A is formed, it is fed into the citric acid cycle, which is also referred to as the Krebs Cycle or the tricarboxylic acid cycle. Here, carbon atoms are oxidized and released one by one as waste products and the energy is conserved. This process occurs in the mitochondrial matrix and occurs twice per molecule of glucose. The two carbon acetyl group from acetyl-CoA is transferred to the four carbon oxaloacetate compound and forms the six carbon molecule citrate. The citrate molecule undergoes isomerization which removes water and then adds water back in to move the hydroxyl group from one carbon atom to another. This produces an isometric form isocitrate. This six carbon isocitrate is oxidized and one molecule of carbon dioxide is removed and the five carbon alpha-ketoglutarate molecule is formed. Also in this step, NAD+ is reduced to NADH and H+. Next, alpha-ketoglutarate becomes oxidized as carbon dioxide is removed. Coenzyme A is added and the four carbon succinyl-CoA compound is formed. Here also, NAD+ is reduced to NADH and H+. In the next step of the citric acid cycle, CoA is removed from the succinyl-CoA compound to produce succinate. This forms a high-energy phosphate linkage to succinate. This phosphate is passed to GDP. GDP and Pi undergo substrate-level phosphorylation to create GTP. This GTP can then be used to make ATP. During the third oxidation step of the citric acid cycle, FAD removes two atoms of hydrogen from succinate to produce fumarate. Also, during this oxidation, FAD is reduced to FADH2. The addition of water to fumarate forms malate which is oxidized to produce oxaloacetate and NAD+ is reduced to NADH and H+. Oxaloacetate is the starting compound of the citric acid cycle and once it is regenerated, it begins a second turn of the cycle. The end products of the citric acid cycle are 6 NADH, 2 FADH2, and 2 GTP. The reduced NADH and H+ molecules along with the FADH2 molecules carry protons and electrons to the electron transport chain which then generates additional ATP through oxidative phosphorylation. Oxidative phosphorylation occurs through chemiosmosis in the inner mitochondrial membrane. Chemiosmosis occurs in two stages. In the first stage, electron transport drives the pump that pumps protons across the membrane. High-energy electrons are passed from FADH2 or NADH to the electron carriers that make up the electron transport chain. These electrons are passed along the electron-transport chain in energy releasing reactions which are coupled to the energy requiring conformational changes in electron carriers that move protons outward across the membrane. As a result, energy being released during electron transport is stored in the form of an electrochemical gradient of protons across the membrane. Eventually, the low energy electrons are transferred to the terminal electron acceptor, O2, which is reduced to water. In the second stage, the proton gradient is harnessed by ATP synthase to make ATP. The movement of protons back across the membrane is done through an ATP-synthesizing enzyme that provides energy which is required to phosphorylate ADP to ATP. Work cited Guyton, Arthur C., and John E. Hall. Textbook of medical physiology. 10th Ed. Philadelphia: Saunders, 2000. Print. Read More