biochemistry note dump for entirety of c785 PDF

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The Cori Cycle

1. The Cori Cycle. The Cori cycle involves the production of lactate by anaerobic cells or cells lacking mitochondria (such as red blood cells), which rely on glycolysis as their sole source of ATP. In these cells, all pyruvate generated by glycolysis is converted to lactate and then exported into the blood. The liver cells take up the lactate and use the gluconeogenesis pathway to convert two molecules of lactate into glucose. This glucose is then transported by the blood back to the cells that rely on glucose for ATP production. The Cori cycle requires that the liver use six ATP molecules to perform gluconeogenesis, while glycolysis in the cells only produces two ATP. As a result, there is a net loss of four ATP in the body. ____6___ molecules of ATP are needed for gluconeogenesis to occur, while only ___2__ ATP are produced by glycolysis.

This means that the Cori cycle results in a net loss of ___4__ ATP per glucose molecule.

2. Glucose is a monosaccharide. It can be used as the raw material to build which one of the following molecules? Select one: a. Nucleic acids b. None of these c. Proteins d. Glycogen. : correct answer is Glycogen. Glycogen is a polysaccharide made up glucose units.

3. Glycolysis is the conversion of glucose to pyruvate. Is this a catabolic process or an anabolic process? Select one: a. None of the these b. Both of these c. Catabolic : Catabolic pathways refer to the breakdown of larger molecules into smaller ones and often produce ATP as a result. Glycolysis is a catabolic process. During glycolysis, a molecule

of glucose is broken down into two molecules of pyruvate and two molecules of ATP are made in the process. d. Anabolic

4. Which of the following is an accurate statement about glycolysis? Select one: a. Glycolysis is the breakdown of a glucose molecule that requires the presence of oxygen. b. Glycolysis results in a net production of four ATP molecules. c. All of these. d. The final products of glycolysis are two molecules of pyruvate.

5. True or False: Glucose is the only food source that can make acetyl Co-A. Select one: a. False b. True

6. In the presence of oxygen, the end products of glycolysis have the potential to enter which one of the following pathways? Select one: a. Glycolysis b. Fermentation c. Citric acid cycle. : In the presence of oxygen, pyruvate forms acetyl Co-A and enters the citric acid cycle, while fermentation occurs in the absence of oxygen. d. None of these

7. In human cells, glycolysis takes place in the cytoplasm. The products of the glycolysis will enter the _________________ to continue with aerobic respiration. Select one: a. mitochondria: The products of glycolysis enter the mitochondria to continue with aerobic respiration.

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b. cytoplasm c. nucleus d. ribosomes

8. NADH and FADH2 are two cofactors made in the citric acid cycle. They then donate the ______________________ they gained in the citric acid cycle to the electron transport chain. Select one: a. ATP b. glucose c. oxygen d. electrons. : Oxygen has a role as the terminal electron acceptor in the electron transport chain.

9. During periods of strenuous exercise the muscle cells can become anaerobic. Without oxygen, the electron transport chain cannot continue and the citric acid cycle slows down. In such situations, how do cells make ATP? Select one: a. There is no requirement for ATP in the muscles. b. Pyruvate remains untransformed. c. Pyruvate produces acetyl Co-A and enters the citric acid cycle. d. Pyruvate is transformed to lactate : In the absence of oxygen, pyruvate is reduced to form lactic acid by fermentation.

10. The citric acid cycle produces large amounts of NADH. If NADH is already abundant in the cell, the enzymes of the citric acid cycle that produce NADH will be inhibited by this product and slow the cycle. Feedback inhibition is the process. The citric acid cycle could be inhibited by high concentrations of ______NADH_________ due to feedback inhibition.

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Oxygen, NADH, Glucose, NAD+ 11. Cyanide binds to complex IV of the electron transport chain, preventing electron transport. Which of the following would be the most immediate effect(s) of cyanide consumption? Select one or more: a. Oxygen would not be consumed by the ETC. b. Protons will not be pumped to the intermembrane space. c. ATP synthase will produce ATP. d. ATP will build up. e. ADP will build up The correct answer is: In an exercising muscle cell under anaerobic conditions, [pyruvate] from glycolysis is turned into [lactate] in order to regenerate [NAD+] for further rounds of glycolysis, which produces [2] ATP per round for the muscle cell to use. The Cori cycle allows [lactate] to be turned into [glucose] via gluconeogenesis in the liver at the expense of [6] ATP. This means that, overall, the Cori cycle creates a deficit of [4] ATP. 12.In an exercising muscle cell under anaerobic conditions, ______pyruvate____ from glycolysis is turned into ___lactate___ in order to regenerate ____NAD+_____ for further rounds of glycolysis, which produces ____2_________ ATP per round for the muscle cell to use. The Cori cycle allows ____lactate____ to be turned into __glucose___ via gluconeogenesis in the liver at the expense of __6____ ATP. This means that, overall, the Cori cycle creates a deficit of ____4_____ ATP. The picture above shows a depiction of an islet of Lanherhans containing alpha cells (purple cells) and beta cells (pink cells). 1. Low blood glucose level (hypoglycemia) stimulates secretion of glucagon from alpha cells of the pancreatic islets. 2. Glucagon acts on hepatocytes (liver cells) to accelerate the conversion of glycogen into glucose (glycogenolysis) and to promote formation of glucose from lactic acid and certain amino acids (gluconeogenesis). 3. As a result, hepatocytes release glucose into the blood more rapidly, and blood glucose level rises. 4. If blood glucose continues to rise, high blood glucose level (hyperglycemia) inhibits release of glucagon (negative feedback). 5. High blood glucose (hyperglycemia) stimulates secretion of insulin by beta cells of the pancreatic islets. 6. Insulin acts on various cells in the body to accelerate facilitated diffusion of glucose into cells, to speed conversion of glucose into glycogen (glycogenesis), to increase uptake of amino acids by cells and to increase protein synthesis, to speed up synthesis of fatty acids (lipogenesis), to slow the conversion of glycogen to glucose (glycogenolysis), and to slow the formation of glucose from lactic acid and amino acids (gluconeogenesis). 7. As a result, blood glucose level falls. 8. If blood glucose level drops below

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normal, low blood glucose inhibits release of insulin (negative feedback) and stimulates release of glucagon. A summary of insulin's effect on glucose metabolism. When insulin binds the insulin receptor (1), it stimluates a number of processes that reduce blood glucose levels. It increases the translocation of GluT4 transporters (2), thus increasing the ability of the cell to import glucose from the blood (3). It also stimulates glycogen production (4), glycolysis (5), and fatty acid synthesis (6). Insulin also inhibits gluconeogenesis (7) to prevent formation of glucose from noncarbohydrate sources.

13.Insulin controls both carbohydrate and fat metabolism. Which of the following statements describes the effects of insulin? Select one: a. Stimulates the glucose uptake b. Inhibits the glycogen breakdown c. Stimulates fatty acid production and storage d. All of these

14.True or False: The defining characteristic of diabetes is the lack of sufficient insulin production. Select one: a. True b. False. : Not all cases of diabetes are due to a lack of insulin production. Diabetes could result from cells resistance to the insulin.

15.The complications of diabetes result from the accumulation of which of the following: Select one: a. None of these b. Fats c. Advanced Glycation End-products (AGEs). : Advanced Glycation End-products

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(AGEs). Increased glucose levels will result in glycation of proteins, which will affect the function of a protein by making it more stiff and inflexible. d. Glycogen

16.The pancreas can regulate and maintain glucose homeostasis by secreting different hormones in response to varying blood glucose levels. The pancreas secretes insulin in response to high blood glucose levels, whereas ______________ is secreted in response to ________________ glucose levels. Select one: a. glucagon, low. : Glucagon is secreted by the pancreas in response to low glucose levels. b. glucagon, high c. insulin, low d. insulin, high

17.While treatment with Metformin is beneficial for many individuals with type 2 diabetes, it does increase the risk of lactic acidosis (accumulation of lactate in the blood that results in lower blood pH) in those who take it. What effect of metformin directly contributes to this potential risk? Select one: a. None of these b. Increased number of GluT4 transporters c. Decreased blood glucose levels d. Decreased gluconeogenesis in the liver : Reduction in liver gluconeogenesis can help lower blood glucose levels in type 2 diabetics. However, it is not without some risk. Recall from the section on the Cori cycle that gluconeogenesis is essential for the conversion of lactate back to glucose after anaerobic fermentation in muscle and red blood cells. Treatment with metformin can, therefore, increase the risk of elevated lactate levels in the blood, a condition known as lactic acidosis because it lowers the blood pH.

18.A risk factor associated with the use of metformin in the treatment of diabetes is lactic acidosis. Acidosis is associated with __a decrease__ in blood pH, due to __an increase_ in the concentration of hydrogen ions (H+). Given this change in blood pH, hemoglobin is more likely to __release__ oxygen.

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a decrease, a stability, an increase, release, bind Glycogen structure Glycogenesis The synthesis of glycogen.

19.Which one of the following non-carbohydrate molecules has the potential to make a glucose molecule? Select one: a. None of these b. Vitamin c. Fatty acids d. Amino acids. : Some kinds of amino acids can create sugar molecules by the process of gluconeogenesis.

20.Carbohydrate loading is a common practice among endurance athletes. Often, three days before a big endurance event, they are known to eat large amounts of complex carbohydrates which leads to the storage of glycogen in their muscles. The stored glycogen increases their endurance by providing a steady supply of glucose during the event by the process of _______________. Select one: a. glycogenesis b. lipolysis c. gluconeogenesis. : Glycogenolysis is the breakdown of glycogen to release glucose. A further breakdown of glucose results in ATP production which helps with the prolonged physical activity in the athletes. d. glycogenolysis

21.Blood glucose levels are controlled by several hormones, mostly ___insulin__ and __glucagon____

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22.Insulin is produced in the _beta_ _cells__ of the pancreas, and is released in response to __increased___ blood glucose levels, whereas __glucagon_ is produced in the _alpha_ cells of the pancrease and is released in response to __low__ blood glucose levels.

23.__Insulin__ stimulates the uptake and storage of glucose from the blood by cells in the body. This results in _increased__ glycogenesis as well as fatty acid synthesis. 24._Glucagon__ stimulates the production of glucose via __gluconeogenesis__ by the liver as well as fatty acid and _amino__ acid catabolism for energy.

25.__Diabetes__ results from a decreased ability to produce insulin or a decreased sensitivity of cells to the insulin produced by the body.

26.What is one available drug that is able to lower blood glucose by affecting the electron transport chain, gluconeogenesis, and glucose transport into cells? Metformin Glucose regulation Glycation The reaction in which a covalent bond forms between a sugar molecule and a protein or lipid molecule without the aid of an enzyme.

27.Which one of the following could result in better outcomes for type 2 diabetics? Select one: a. An increased number of GluT4 transporters in the cell membrane. : In Type 2 diabetics, the number of glucose transporters in the target cells is decreased leading to inefficient uptake of glucose by the cells. Increasing the amount of transporters will increase the rate of glucose absorption by the cells. b. An increased A1C percentage. c. An increased rate of gluconeogenesis in the liver. d. Lower production of insulin.

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28.Emma was prescribed metformin which is used to control blood glucose levels. One direct effect of metformin is inhibition of the ------------------------- pathway in the liver. Select one: a. Glycolysis b. None of these c. Gluconeogenesis. : Metformin is a drug of choice for treating Type 2 diabetes. One of the direct actions of the drug in controlling the blood sugar levels is by inhibiting gluconeogenesis in the liver d. Citric acid cycle

29.Emma has an A1C level of 7.0% in her blood. A1C is a form of__________________. Select one: a. Hormone b. Hemoglobin. : In the presence of excessive amounts of glucose in the blood, glucose makes a covalent bond to the hemoglobin protein in a reaction known as glycation. A1C is the glycated form of hemoglobin. c. Insulin d. Enzyme

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