Endo Carb Metab MCQ's

The patient has not eaten solid food for 8 hours. During fasting, the body initially relies on glycogen stores in the liver to maintain blood glucose levels. After approximately 8-12 hours of fasting, glycogen stores become depleted, and the body starts to produce glucose through a process called gluconeogenesis. Therefore, the finding that the patient is producing most of his blood glucose from glycogen suggests that he has not eaten solid food for 8 hours.

GLUT translocases have primary responsibility for glucose transport in liver. There are other glucose translocases, not influenced by insulin under normal circumstances.

Excessive consumption of fructose, which is found in high amounts in soft drinks like cola, can contribute to the accumulation of triglycerides in adipose tissue. Triglycerides are a type of fat, and when they are stored in excess, it can lead to weight gain and an increased risk of obesity. Therefore, it is recommended for the patient to reduce their intake of dietary fructose, including cola, in order to prevent the storage of triglycerides in adipose tissue and maintain a healthy weight.

The infant's symptoms are consistent with the genetic disorder called "POMPE's GSD" or Infantile-onset Type II GSD. This disorder is characterized by the accumulation of glycogen in lysosomes, leading to cardiomegaly, hepatomegaly, feeding difficulties, and generalized muscle weakness. This accumulation of glycogen in lysosomes is the underlying cause of the infant's symptoms.

Reciprocal regulation refers to a relationship where the activity of one enzyme is increased while the activity of the other enzyme is decreased, and vice versa. In the case of glycogen synthase and glycogen phosphorylase, they are both involved in the regulation of glycogen metabolism. Glycogen synthase adds glucose units to glycogen, while glycogen phosphorylase breaks down glycogen to release glucose. When glycogen phosphorylase is active and breaking down glycogen, glycogen synthase is inhibited. Conversely, when glycogen synthase is active and adding glucose units to glycogen, glycogen phosphorylase is inhibited. This reciprocal regulation ensures a balanced control of glycogen metabolism.

Overnight fasting releases glucagon in amounts which stimulate glycogenolysis. Prolonged fasting and depletion of glycogen stores results in activation of gluconeogenesis.

Insulin stimulates glycogen synthase and phosphofructokinase-1, which are enzymes involved in the storage and breakdown of glucose. Glycogen synthase helps convert glucose into glycogen for storage in the liver and muscles, while phosphofructokinase-1 is involved in the breakdown of glucose for energy production. By stimulating these enzymes, insulin helps to lower blood glucose levels by promoting the storage of glucose as glycogen and inhibiting its breakdown for energy.

The possible enzyme responsible for the given results is Glycogen Phosphorylase. This is because the activity of this enzyme is significantly increased after glucagon treatment, as indicated by the obscured result of 90. The other enzymes, Citrate Synthase, Enolase, and Phosphoglucomutase, show no significant change in activity before and after glucagon treatment, as their results remain the same at 10. Therefore, Glycogen Phosphorylase is the most likely enzyme responsible for the observed increase in activity after glucagon treatment.

Glycogen Phosphorylase is the enzyme responsible for breaking down glycogen into glucose-1-phosphate, which can then be used as a source of energy. In this patient, the muscle biopsy revealed that glucose is not responsive to changes in calcium concentration, suggesting a deficiency in Glycogen Phosphorylase. This deficiency would impair the breakdown of glycogen, leading to a decrease in glucose availability for energy production during exercise, resulting in muscle cramps and fatigue.

The appearance of ketone bodies in the urine is well documented in patients with uncontrolled type I diabetes. This is because in the absence of insulin, glucose cannot enter cells to be used as energy, so the body starts breaking down fats for energy instead. This leads to the production of ketone bodies, including acetoacetate, which are excreted in the urine. A high fat, low carbohydrate diet can also result in increased production of ketone bodies because the body is not getting enough carbohydrates to use as energy, so it turns to breaking down fats instead. This is known as nutritional ketosis.

A partial deficiency of an enzyme in the glycolytic pathway can lead to impaired energy production in red blood cells, resulting in a decreased number of healthy red blood cells and ultimately causing anemia. This is because glycolysis is an essential metabolic pathway for red blood cells to generate energy. Therefore, anemia is the most likely presenting symptom for a patient with this deficiency.

Fructose 2,6 bisphosphate controls PFK-1 activity (activates) allosterically. It also regulates Fructose 1, 6 bisphosphatase by comp. inhibition. (Fructose 1,6-bisphosphate is a glycolytic intermediate, not an enzyme effector).

AMP activates the activity of glycogen phosphorylase in muscle tissues. Divalent calcium is also a similar allosteric effector of glycogen phosphorylase in liver.

The high insulin levels in a patient with an insulinoma will inhibit the activity of protein phosphatase-1, which in turn will inhibit glycogen phosphorylase. Glycogen phosphorylase is responsible for breaking down glycogen into glucose in the liver. Therefore, the inhibition of glycogen phosphorylase will result in decreased glucose production from glycogen, limiting glycolysis and ATP generation. This is consistent with the statement "Glycolysis and ATP generation will be limited."

Anaerobic glycolysis produces 2 ATP per glucose metabolized. Lactate is the product formed from pyruvate to allow cycling of NAD+.

A patient who lacks all but 5% of the activity of the enzyme glycogen phosphorylase a will have a condition similar to another patient with a near total deficiency of the glycogen debranching enzyme. Both enzymes are involved in glycogen metabolism. Glycogen phosphorylase a breaks down glycogen into glucose-1-phosphate, while the glycogen debranching enzyme helps in the breakdown of glycogen by removing branch points. Therefore, a deficiency in either enzyme would result in impaired glycogen breakdown and similar signs and symptoms.

Insulin is a hormone that plays a crucial role in regulating blood sugar levels. It helps to lower blood sugar by promoting the uptake of glucose into cells. The options given in the question are all activities of insulin except for the activation of fructose1,6 bisphosphatase activity in the liver. Fructose1,6 bisphosphatase is an enzyme involved in gluconeogenesis, the process of producing glucose from non-carbohydrate sources. Insulin actually inhibits the activity of fructose1,6 bisphosphatase, as it promotes glucose uptake and storage rather than glucose production. Therefore, the correct answer is the activation of fructose1,6 bisphosphatase activity in the liver.

Aldolase A being "fast" and Aldolase B not being fast implies that Aldolase A has a higher catalytic efficiency or activity compared to Aldolase B. This difference in enzymatic activity can have clinical implications as it may affect the rate of carbohydrate metabolism and energy production in cells. It could potentially impact the overall metabolic function and health of an individual.

Both gluconeogenesis and glycogenolysis result in formation of glucose-6-phosphate which can be converted to free glucose by only one enzyme found in liver: Glucose-6-phosphatase.

Excess fructose depletes inorganic phosphate, which is an essential component for energy production in the body. Without an adequate supply of inorganic phosphate, the body's ability to generate energy is compromised, leading to chronic fatigue. This is why someone following a fructose-only diet, like fruititarians, may experience chronic fatigue as a result of the depletion of inorganic phosphate caused by excess fructose consumption.

Glucokinase has a Km in the physiological range of blood glucose, which means that it has a high affinity for glucose at normal blood glucose concentrations. As glucose concentrations rise in the well-fed state, the increased availability of glucose allows glucokinase to bind to and phosphorylate more glucose molecules, resulting in an increase in its activity. This is because the Km value represents the concentration of substrate needed for an enzyme to reach half of its maximum velocity (Vmax), so when glucose concentrations are within the physiological range, glucokinase is able to function optimally.

Glucose-6-phosphatase is the correct answer because it is the enzyme responsible for the final step in both liver glycogenolysis and liver gluconeogenesis. It converts glucose-6-phosphate into glucose, which can then be released into the bloodstream. By inhibiting the activity of glucose-6-phosphatase, both processes will be shut down simultaneously.

Fatty-acyl-CoA’s are substrates for beta oxidation in mitochondria (catabolism). Acetyl-CoA is a 2 carbon substrate attached to CoA which serves as the allosteric effector of pyruvate carboxylase.

The low glucose measurement in the patient could be due to the insufficient circulating fatty acids. Gluconeogenesis is the process of synthesizing glucose from non-carbohydrate sources, such as fatty acids, in the liver. In this case, the patient's free fatty acid levels are very low, which means that there is a lack of substrates for gluconeogenesis. As a result, the liver is unable to produce enough glucose, leading to the low glucose measurement. This could be a consequence of the patient's history of alcohol abuse, as alcohol metabolism competes with gluconeogenesis enzymes and may deplete the supply of fatty acids available for glucose synthesis.

In Von Gierke Disease, there is a deficiency of glucose-6-phosphatase, which is required for the breakdown of glycogen. As a result, glycogen cannot be broken down properly and accumulates in the body. The "b" form of glycogen synthase is responsible for the production of glycogen. In this disease, the "b" form of the enzyme will be allosterically activated, meaning it will be more active than normal. This increased activity of glycogen synthase will lead to the production of more glycogen, further contributing to its accumulation in the patient.

At least five ‘proteins or enzymes’, many more genes are involved because some of the translocases are multi-subunit, derived from multiple genes.