Clinical cases and Situational tasks
157. What substances are used for the synthesis of glucose in the human body during prolonged fasting or exhausting work? Explain your answer.
Answer: In such conditions, synthesis of glucose is possible from noncarbohydrate compounds by gluconeogenesis. These metabolites are lactic and pyruvic acids, glycogenic amino acids, glycerol.
158. Explain the negative impact of excessive intake of carbohydrates on the human body. Which biochemical disorders it causes?
Answer: Excessive consumption of carbohydrates leads to the synthesis of lipids, obesity, atherosclerosis, development of cardiovascular diseases.
159. Examination of a patient revealed increased activity of LDH1, LDH2 and creatine. What human organ might be damaged?
Answer: Increased activity of LDH1, LDH2 and creatine in blood serum indicates development of pathological process in heart muscle.
160. Diastase was not indicated in the urine of a patient during biochemical investigations. Explain results of the test.
Answer: Deficiency of diastase in patients’ urine indicates acute renal failure.
161. A patient was transported to the hospital. Examination revealed the next indexes: concentration of blood glucose – 10 mmol/l, concentration of glucose in urine – 5.5%, concentration of ketone bodies in blood serum – increased. What is the most likely diagnosis?
Answer: The above symptoms indicate hyperglycemic coma.
162. A female infant appeared normal at birth but developed signs of liver disease and muscular weakness at 3 months. She had periods of hypoglycemia, particularly on awakening. Examination revealed an enlarged liver. Laboratory analyses following fasting revealed ketoacidosis, blood pH 7.25, and elevations in both alanine transaminase (ALT) and aspartate transaminase (AST). Administration of glucagon following a carbohydrate meal elicited a normal rise in blood glucose, but glucose levels did not rise when glucagon was administered following an overnight fast. Liver biopsy revealed an increase in the glycogen content (6 percent of wet weight). Deficiency of what enzyme is a most likely for this patient? Explain your answer.
Answer: Definitive diagnosis would await analysis of the glycogen structure and enzyme activities, but the hepatomegaly, increased liver glycogen content, fasting hypoglycemia, and muscle weakness are consistent with Cori disease, glycogen storage disease type III. The increase in glycogen content results from an inability to degrade glycogen beyond the limit dextrin of phosphorylase. A deficiency in the debranching enzyme leaves glycogen with short outer branches.
163. Fill in the blanks:
Answer:
164. The glucose-alanine cycle is used primarily as a mechanism for skeletal muscle to eliminate nitrogen while replenishing its energy supply.
Put requirements and production of ATP into their place in glucose-alanine cycle presented in the picture below.
Explain biological significance of glucose-alanine cycle in humans.
Answer:
a.
b. Glucose oxidation produces pyruvate which can undergo transamination to alanine. This reaction is catalyzed by alanine transaminase, ALT (ALT used to be called serum glutamate-pyruvate transaminase, SGPT). Additionally, during periods of fasting, skeletal muscle protein is degraded for the energy value of the amino acid carbons and alanine is a major amino acid in protein. The alanine then enters the blood stream and is transported to the liver. Within the liver alanine is converted back to pyruvate which is then a source of carbon atoms for gluconeogenesis. The newly formed glucose can then enter the blood for delivery back to the muscle. The amino group transported from the muscle to the liver in the form of alanine is converted to urea in the urea cycle and excreted.
165. Indicate enzymes catalyzing the following reactions of HMP:
Answer: 1 – glucose-6-phosphate dehydrogenase, 2 – lactonase, 3 – 6-phosphogluconate dehydrogenase