Questions to study.
1. Pentose phosphate pathway of glucose oxidation, its oxidative and non-oxidative stage. Its biological significance.
2. Gluconeogenesis: substrates, key reaction (bypass of irreversible glycolysis reactions), regulation, and significance.
3. Cori cycle. Glucose-alanine cycle.
4. Regulation of carbohydrate metabolism.
5. Metabolism of fructose and galactose and their hereditary disorders.
Assignment for self-instruction
| | Guidelines for performing the task |
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| Study about gluconeogenesis | 1. Write down three irreversible reactions of glycolysis and their bypass reactions. 2. Write down a scheme of gluconeogenesis from amino acids, glycerol, lactic acid, keto acids. 3. Calculate the energy efficiency (amount of ATP molecules) for synthesis of glucose from lactic acid. 4. Name the tissues that are capable of synthetizing glucose. 5. Study the regulation of gluconeogenesis. 6. Explain the Cori cycle and make a schematic drawing |
Ending of the table
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| Study apotomic glucose oxidation (pentose phosphate pathway, PPP) | 1. Write down the stages of PPP. 2. Write down chemical reactions of oxidative stage of PPP. 3. Write down a scheme of nonoxidative stage of PPP. 4. Write down key enzymes of both stages of PPP. 5. Characterize the biological significance of PPP. 6. Determine common metabolites for apotomic and dichotomic glucose oxidation |
| Study the features of fructose and galactose metabolism in human body | 1. Write down reactions of fructose metabolism catalized by fructokinase and fructose 1-phosphate aldolase. 2. Write down reactions of convertion of galactose into glucose 6-phos-phate. 3. Characterize fructosuria and galactosemia as ensymopathies |
| Study the mechanisms of maintaining glucose blood level | 1. Define in writing the terms hyperglycemia and hypoglycemia. 2. Indicate the reference level of glucose in the blood. 3. Name hyperglycemic and hypoglycemic hormones. 4. Write down a scheme of self-regulation of glucose blood levels. 5. Define in writing the terms renal threshold for glucose and glycosuria. What is renal threshold quantitatively? Which diseases are accompanied by glycosuria? 6. Study glucose tolerance test and draw the sugar curves in diabetes mellitus |
| Study regulation of carbohydrate metabolism | 1. Characterize the cellular and neurohumoral level of regulation of carbohydrate metabolism. 2. Describe the role of the nervous system in regulation of carbohydrate metabolism. 3. Write down rate-limiting allosteric enzymes of glycogen breakdown, glycolysis, gluconeogenesis, PPP. 4. Determine the points of action of glucagon, epinephrine, glucocorti-coids, growth hormone, insulin on carbohydrate metabolism |
Library-research paper
1. Metabolism of galactose and its disorders.
LABORATORY WORK 1. Revealing anaerobic glycolysis in muscle tissue
Glucose breaks down to yield lactic acid in anaerobic conditions: glucose + 2 ADP + 2H3PO4 → lactate + 2 ATP + 2H2O
Anaerobic glycolysis is accompanied by phosphorylation of ADP, as you can see from the net equation. In spite of small output of ATP, this process is very important in energy supplement of cells. Moreover, it is a single source of energy for erythrocytes. The role of anaerobic glycolysis in energy supplement of cells increases dramatically in hypoxic condition when partial pressure of oxygen decreases.
Anaerobic glycolysis induces a decrease in glucose content while lactate content increases. Taking into account this fact, the decrease in glucose level can be used in reaction mixture to reveal glycolysis. Addition of sodium fluoride to the reaction mixture causes cessation of glycolysis thus preventing any further decrease in glucose level.
Procedure
► Take 3 tubes. Pour 2 ml of 0.1 M phosphate buffer with pH 8.0 and 1 ml of 1% glucose solution into each one.
► Add 1 ml of 10% trichloroacetic acid (TCA) to tube 1, and 0.2 ml of 3 M sodium fluoride solution to tube 2.
► Thoroughly cut muscle tissue with scissors, and then add 0.5 g of muscle tissue to each one of three tubes and mix well.