Biochemistry MCQs with Answer and Explanations | Chapter 6

Answer: Viral hepatitis

AST (Aspartate aminotransferase) and ALT (Alanine aminotransferase) are liver enzymes. When the liver is damaged, these enzymes are released into the bloodstream, causing elevated levels. Viral hepatitis is a liver inflammation caused by a virus, resulting in liver damage and, consequently, increased AST and ALT levels.

The other options are incorrect:

• Infectious mononucleosis: Caused by Epstein-Barr virus, typically affects the lymphatic system, not the liver.
• Muscular dystrophy: Primarily affects muscles, not the liver.
• Pulmonary emboli: Relates to blood clots in the lungs, unrelated to liver function.

Answer: Intestine

Urobilinogen is formed in the intestine. It is a byproduct of the breakdown of hemoglobin from red blood cells. Bilirubin, produced in the liver, is converted to urobilinogen by intestinal bacteria.

The other options are incorrect:

• Kidney: Primarily involved in filtering blood and producing urine.
• Spleen: Primarily involved in filtering old red blood cells and producing platelets.
• Liver: While involved in bilirubin metabolism, urobilinogen is formed after bilirubin reaches the intestines.

Answer: A false increase in Hct value

Insufficient centrifugation may result in incomplete separation of the blood components. This can leave some plasma in the packed red blood cell layer, causing the hematocrit (Hct) value to appear falsely elevated.

The other options are incorrect:

• A false decrease in Hct value: Insufficient centrifugation typically does not cause a false decrease in the Hct value, as the incomplete separation of plasma usually increases the measured red cell layer.
• No effect on Hct value: Insufficient centrifugation does affect the Hct value because it disrupts the proper separation of blood components, leading to an inaccurate measurement.
• All of the above depending on the patient: The effect of insufficient centrifugation is consistent and typically results in a false increase in Hct value, not varying based on the patient.

Answer: Urea

Urea is found in the highest concentration in urine. It is the primary waste product formed from the breakdown of proteins and is excreted by the kidneys.

The other options are incorrect:

• Uric acid: A waste product from nucleic acid metabolism, but its concentration is lower than urea in urine.
• Glucose: Normally not present in significant amounts in urine. Its presence indicates abnormal conditions like diabetes.
• Creatinine: A waste product of muscle metabolism, but its concentration is lower than urea in urine.

Answer: Glucosuria

Glucosuria is the term used to describe the presence of glucose in the urine. This condition typically occurs when blood glucose levels are high, such as in uncontrolled diabetes, and the kidneys cannot reabsorb all the glucose, leading to its excretion in the urine.

The other options are incorrect:

• Uremia: Refers to the presence of excessive amounts of urea and other waste products in the blood.
• Glucose intolerance: A condition where the body cannot effectively use glucose, but it doesn’t directly refer to glucose in the urine.
• Ureteritis: Inflammation of the ureter, unrelated to glucose in the urine.

Answer: False

The normal serum osmolarity range is significantly different from 50-100 mOsm. The actual normal range is typically between 275 and 295 mOsm/kg.

The other options are incorrect:

• True: This option is incorrect because a serum osmolarity of 50-100 mOsm is far below the normal range. Such low levels would indicate a serious imbalance and are not compatible with normal physiological conditions.

Answer: Valincomycin

Valincomycin is a common component of potassium ion-selective electrodes (ISEs). This antibiotic has a specific affinity for potassium ions, allowing it to selectively bind and measure potassium concentration.

The other options are incorrect:

• Silver chloride: Commonly used in reference electrodes, not potassium ISEs.
• Potassium selective membrane: This is too general and doesn’t specify the material used.

Answer: A high carbohydrate diet for 3 days

Before undergoing glucose tolerance testing, a patient should consume a high carbohydrate diet (typically 150 grams or more per day) for at least 3 days. This ensures that the body is adequately prepared for the test and helps to avoid false results.

The other options are incorrect:

• A low carbohydrate diet for 3 days: This would deplete glycogen stores and interfere with the test results.
• Fasting for 48 hours prior to testing: Prolonged fasting can lead to hypoglycemia and affect glucose tolerance.
• Bed rest for 3 days: Bed rest is not a standard preparation for a glucose tolerance test and would not influence the results.

Answer: 100 mg/dl (5.5 mmol/L)

A fasting glucose of 90 mg/dl is within the normal range. Normal glucose metabolism implies that the body effectively handles a glucose load. Therefore, a postprandial glucose level that returns to near-normal levels (around 100 mg/dl) within two hours of eating would indicate normal glucose metabolism.

The other options are incorrect:

• 55 mg/dl (3.0 mmol/L): This is hypoglycemic and abnormal.
• 180 mg/dl (9.9 mmol/L): This is hyperglycemic and suggests impaired glucose tolerance.
• 260 mg/dl (14.3 mmol/L): This is significantly hyperglycemic and indicative of diabetes mellitus.

Answer: 50 mg/dl (2.3 mmol/L)

The glucose level in the cerebrospinal fluid (CSF) is typically around 60-70% of the blood glucose level. Therefore, with a blood glucose of 80 mg/dl, a CSF glucose of 50 mg/dl would be within the normal range.

The other options are incorrect:

• 150 mg/dl (8.3 mmol/L): This is extremely high and not possible for CSF glucose levels.
• 25 mg/dl (1.4 mmol/L): This is significantly lower than normal and would suggest an issue, such as meningitis.
• 100 mg/dl (5.5 mmol/L): This is higher than expected for CSF glucose and would be abnormal.

Answer: Analyzed immediately

Glucose levels in cerebrospinal fluid (CSF) can decrease over time due to glycolysis by cells present in the fluid. To obtain accurate results, the CSF sample should be analyzed as soon as possible after collection.

Incorrect Options:

• Stored at room temperature: This would accelerate glycolysis and lead to inaccurate results.
• Refrigerated: Refrigeration can slow down glycolysis but doesn’t prevent it entirely. Immediate analysis is still preferred.
• Heated to 56 degrees celsius: Heating would denature enzymes and proteins, affecting the glucose measurement.

Answer: 200 mg/dl (11. mmol/L)

A 2-hour postprandial glucose value of 200 mg/dl or higher is considered diagnostic for diabetes mellitus. This indicates the body’s inability to effectively manage blood glucose levels after a meal.

The other options are incorrect:

• 180 mg/dl (9.9 mmol/L): This is also above the normal range but still within the impaired glucose tolerance category.
• 160 mg/dl (8.8 mmol/L): While this is elevated, it falls within the range of impaired glucose tolerance and is not diagnostic of diabetes.
• 170 mg/dl (9.4 mmol/L): Similar to the previous option, this value is elevated but doesn’t meet the diagnostic criteria for diabetes.

Answer: Lower than adults

Pre-term or low birth weight infants have lower glycogen stores and less developed glucose regulation systems compared to adults. As a result, their blood glucose levels can drop significantly, and the definition of hypoglycemia for these infants is lower than that of adults.

The other options are incorrect:

• The same as adults: This is incorrect because infants have different metabolic needs and glucose regulation.
• The same as a normal full-term infant: While closer than the adult value, pre-term or low birth weight infants still have specific glucose requirements.
• Higher than a normal full-term infant: This is opposite to the correct answer. Their glucose levels are typically lower, not higher.

Answer: Glycolysis

Glycolysis is the metabolic process that converts glucose or other hexoses into lactate or pyruvate. This process occurs in the cytoplasm of cells and is the first step in both aerobic and anaerobic respiration.

The other options are incorrect:

• Glycogenesis: This is the process of converting glucose into glycogen for storage.
• Gluconeogenesis: This is the process of creating glucose from non-carbohydrate sources.
• Glycogenolysis: This is the breakdown of glycogen into glucose.

Answer: Fasting plasma glucose= 126 mg/dl

A fasting plasma glucose level of 126 mg/dL or higher is diagnostic of diabetes mellitus. This value meets the criteria for diabetes according to the American Diabetes Association, which defines diabetes as a fasting glucose level of 126 mg/dL or more.

The other options are incorrect:

• 2hr specimen = 150 mg/dL: A 2-hour postprandial glucose level of 150 mg/dL is elevated but does not meet the threshold for diagnosing diabetes. The diagnostic criterion for diabetes is a 2-hour postprandial glucose level of 200 mg/dL or higher.
• Fasting plasma glucose = 110 mg/dL: A fasting plasma glucose level of 110 mg/dL is considered to be within the normal range or indicative of prediabetes, but it does not meet the criteria for diagnosing diabetes, which requires a fasting glucose level of 126 mg/dL or higher.
• 2hr specimen = 180 mg/dL: Although this 2-hour postprandial glucose level is elevated, it is below the diagnostic threshold for diabetes. Diabetes is diagnosed with a 2-hour glucose level of 200 mg/dL or more.

Answer: 6-8 weeks

Glycated hemoglobin (HbA1c) reflects the average blood glucose level over the preceding 6-8 weeks. This is because the lifespan of red blood cells, where hemoglobin is found, is approximately 8-12 weeks.

The other options are incorrect:

• 1-3 weeks: This is too short a timeframe for HbA1c to accurately reflect glucose levels.
• 4-5 weeks: This is closer but still underestimates the actual timeframe.
• 16-20 weeks: This is significantly longer than the lifespan of red blood cells and does not accurately represent HbA1c’s timeframe.

Answer: Hemoglobin A1c

Hemoglobin A1c (HbA1c) provides a long-term (2-3 month) average of blood glucose levels. It is the most reliable and widely used indicator for monitoring long-term glucose control in patients with diabetes.

The other options are incorrect:

• 2hr postprandial serum glucose: This measures glucose levels after a meal, but it doesn’t give a comprehensive picture of long-term glucose control.
• Weekly fasting 7am serum glucose: This only reflects a single point in time and doesn’t provide information about overall glucose control.
• Glucose tolerance testing: This is used for diagnosing diabetes, not for routine monitoring of long-term glucose control.

Answer: Average blood glucose levels of the past 2-3 months

Glycosylated hemoglobin (HbA1c) is a measure of the average blood glucose level over the past 2-3 months. This is because the lifespan of red blood cells, where hemoglobin is found, is approximately 8-12 weeks. Hemolysis, or the breakdown of red blood cells, does not alter this fundamental principle.

The other options are incorrect:

• Hemoglobin a1c level at the time the sample is drawn: This is redundant; the question itself asks about glycosylated hemoglobin levels, which is synonymous with HbA1c.
• Average blood glucose levels for the past week: HbA1c reflects a much longer period than one week.
• Blood glucose level at the time the sample drawn: HbA1c is not a measure of a single point in time but rather an average over several weeks.

Answer: A1c

Hemoglobin A1c (HbA1c) is formed when glucose irreversibly attaches to the N-terminal valine of the beta chain of hemoglobin. This glycosylation process reflects the average blood glucose level over the past 2-3 months.

The other options are incorrect:

S, C, and A2: These are different types of abnormal hemoglobin variants, unrelated to glucose attachment.

Answer: Show a decrease in glycated hgb value

Glycated hemoglobin (HbA1c) reflects average blood glucose over the past 2-3 months. In hemolytic anemia, red blood cells are destroyed prematurely. Since HbA1c is formed within red blood cells, a decreased lifespan of these cells leads to a lower HbA1c value, even if blood glucose levels are normal.

The other options are incorrect:

• Demonstrate an elevated hgb A1: This is incorrect. HbA1c would decrease, not increase, in hemolytic anemia.
• Show an increase in glycated hgb value: This is incorrect as hemolytic anemia results in a shorter lifespan for red blood cells.
• Show lil or no change in glycated hgb value: This is not accurate as there is a direct relationship between red blood cell lifespan and HbA1c.

Answer: Hgb S

In the presence of hemoglobin S (HbS), which is associated with sickle cell disease, ion-exchange chromatography methods for measuring HbA1c might show falsely increased levels of HbA1c. This is due to the altered properties of HbS that can interfere with the measurement.

The other options are incorrect:

• Iron deficiency anemia: Iron deficiency anemia does not typically cause falsely increased HbA1c levels. It can affect overall hemoglobin levels but does not interfere with the specific measurement of HbA1c.
• Pernicious anemia: Pernicious anemia affects vitamin B12 absorption and can impact red blood cell production but does not usually cause falsely increased HbA1c levels.
• Thalassemias: While thalassemias can affect hemoglobin structure and levels, they are more likely to cause falsely decreased HbA1c levels rather than increased levels. They do not generally lead to false increases in HbA1c measurement.

Answer: Carbohydrates

Acetone is a ketone body, produced primarily during the breakdown of fats for energy when there is insufficient glucose (carbohydrate) availability. Thus, an increase in serum acetone indicates a defect in carbohydrate metabolism.

The other options are incorrect:

• Uric acid: Waste product from nucleic acid metabolism, unrelated to fat or carbohydrate metabolism.
• Fat: While acetone is produced from fat breakdown, the underlying issue is insufficient carbohydrate metabolism.
• Urea: Related to protein metabolism, not fat or carbohydrate metabolism.
• Nitrogen: Component of proteins and amino acids, unrelated to ketone body production.

Answer: H2 breath test

The H2 breath test is the best method to diagnose lactase deficiency. It measures the amount of hydrogen in the breath after the ingestion of lactose. Increased hydrogen levels indicate that lactose is not being properly digested and is being fermented by bacteria in the colon, which is a sign of lactase deficiency.

The other options are incorrect:

• D-xylose test: This test is used to assess small intestinal absorption, but it’s not specific for lactose malabsorption.
• Plasma adolase level: Adolases are enzymes involved in glycolysis, not directly related to lactose digestion.
• LDH level: LDH is a general enzyme found in many tissues, not specific to lactose digestion.

Answer: Metabolic acidosis

The kidneys play a crucial role in maintaining acid-base balance by excreting excess acid. In chronic renal failure, the kidneys’ ability to eliminate acid is impaired, leading to a buildup of acid in the blood, resulting in metabolic acidosis.

The other options are incorrect:

• Respiratory alkalosis: Caused by hyperventilation, leading to excessive carbon dioxide elimination.
• Respiratory acidosis: Primarily caused by impaired carbon dioxide elimination by the lungs, not the kidneys.
• Metabolic alkalosis: Characterized by excessive bicarbonate levels, typically due to loss of gastric acid or excessive alkali intake.

Answer: Metabolic acidosis

Severe diarrhea leads to excessive loss of fluids and electrolytes, particularly bicarbonate, which is essential for maintaining acid-base balance. The loss of bicarbonate results in a decrease in blood pH, leading to metabolic acidosis.

The other options are incorrect:

• Respiratory alkalosis: Caused by hyperventilation, leading to excessive carbon dioxide elimination.
• Respiratory acidosis: Primarily caused by impaired carbon dioxide elimination by the lungs.
• Metabolic alkalosis: Characterized by excessive bicarbonate levels, typically due to loss of gastric acid or excessive alkali intake.

Answer: Diffusion characteristics of the membrane

The PCO2 electrode relies on the diffusion of carbon dioxide gas through a membrane to reach equilibrium. The rate of diffusion is influenced by the membrane’s properties, such as its thickness and permeability. Therefore, the diffusion characteristics of the membrane are the primary factor determining the time required for the electrode to reach equilibrium.

The other options are incorrect:

• Potential of the polarizing mercury cell: This relates to the electrode’s internal components and does not impact the diffusion of carbon dioxide through the membrane.
• Actual blood pO2: The oxygen tension in the blood does not directly affect the diffusion of carbon dioxide through the PCO2 electrode membrane.
• Type of calibrating standard: The calibration standard used can affect the accuracy of the measurement but does not influence the time taken to reach equilibrium.

Answer: Respiratory acidosis

Emphysema is a condition where the alveoli (tiny air sacs in the lungs) are damaged, reducing their ability to exchange oxygen and carbon dioxide. When fluid accumulates in these already compromised alveoli, it further hinders gas exchange. The inability to effectively expel carbon dioxide leads to a buildup of CO2 in the blood, resulting in respiratory acidosis.

The other options are incorrect:

• Metabolic alkalosis: Characterized by excessive bicarbonate levels, typically due to loss of gastric acid or excessive alkali intake.
• Respiratory alkalosis: This occurs when there’s excessive elimination of CO2, which is opposite to the scenario described.
• Metabolic acidosis: Primarily caused by issues with kidney function or acid production.

Answer: 20:1

The bicarbonate to carbonic acid ratio is crucial for maintaining blood pH. At a normal pH of 7.40, this ratio is approximately 20:1. This balance is essential for proper bodily function.

The other options are incorrect:

• 30:1: This ratio is significantly higher than normal and would indicate a severe imbalance towards alkalosis.
• 15:1: This ratio is lower than the normal range and would indicate a tendency towards acidosis.
• 25:1: This ratio is higher than the normal range and would indicate a tendency towards alkalosis.

Answer: 7.35-7.45

The normal pH range for arterial blood, measured at 37 degrees Celsius, is crucial for maintaining proper bodily functions. A pH below this range indicates acidosis, while a pH above this range suggests alkalosis.

The other options are incorrect:

• 7.45-7.50: This range is higher than normal and would indicate a tendency towards alkalosis.
• 7.28-7.34: This range is lower than normal and would indicate acidosis.
• 7.33-7.37: This range is lower than the normal range and would indicate a tendency towards acidosis.

Answer: Hyperventilation

Hyperventilation, or rapid and deep breathing, leads to excessive elimination of carbon dioxide from the body. This decrease in carbon dioxide levels results in a rise in blood pH, causing respiratory alkalosis.

The other options are incorrect:

• Asthma: While asthma can cause rapid breathing, it doesn’t necessarily lead to hyperventilation and respiratory alkalosis.
• Vomiting: Primarily associated with metabolic alkalosis due to loss of stomach acid.
• Starvation: Can lead to metabolic acidosis due to the breakdown of fatty acids.

Answer: Elevated lipid levels

Indirect ion-selective electrode (ISE) methods for sodium determination involve diluting the sample. In cases of elevated lipid levels (hyperlipidemia), the sample is more viscous, and the dilution factor becomes inaccurate. This leads to a falsely decreased sodium result.

The other options are incorrect:

• Decreased albumin levels: Similar to decreased protein levels, this can cause pseudohypernatremia, not falsely decreased sodium.
• Elevated chloride levels: Chloride levels do not directly interfere with sodium measurement by indirect ISE.
• Decreased protein levels: This can actually lead to a falsely increased sodium result, a condition known as pseudohypernatremia.

Answer: 40%-50%

Approximately 40-50% of total serum calcium is bound to proteins, primarily albumin. This portion is considered non-diffusible as it cannot pass through membranes.

The other options are incorrect:

• 10%-30%: This percentage is too low for protein-bound calcium.
• 80%-90%: This percentage is too high for protein-bound calcium.
• 51%-60%: This is close but slightly higher than the actual range.

Answer: Parathyroid hormone

Parathyroid hormone (PTH) is the primary regulator of serum calcium levels. It increases calcium levels by stimulating bone resorption, increasing calcium reabsorption in the kidneys, and promoting calcium absorption in the intestines.

The other options are incorrect:

• Vitamin C: Essential for various functions but not directly involved in calcium regulation.
• Insulin: Primarily regulates blood glucose levels.
• Thyroxine: Primarily regulates metabolism.

Answer: Parathyroid

The parathyroid glands are primarily responsible for regulating calcium and phosphorus metabolism. They produce parathyroid hormone (PTH), which plays a crucial role in maintaining calcium levels in the blood.

The other options are incorrect:

• Pituitary: Controls several hormones but not directly involved in calcium and phosphorus regulation.
• Thyroid: Primarily involved in regulating metabolism.
• Adrenal glands: Involved in stress response and electrolyte balance, but not primarily calcium and phosphorus.

Answer: Calcium

Tetany is a condition characterized by muscle cramps and spasms due to low calcium levels. Therefore, a calcium test would be the most appropriate to confirm or rule out hypocalcemia as the cause of the neuromuscular irritability.

The other options are incorrect:

• Glucose: Primarily related to carbohydrate metabolism and is not indicative of calcium levels or muscle function.
• Phosphate: While related to calcium homeostasis, it’s not the primary indicator for tetany.
• BUN: Measures kidney function and is not directly related to calcium or muscle irritability.

Answer: Magnesium

Magnesium is essential for proper neuromuscular function and works closely with calcium. Hypomagnesemia can often mimic or exacerbate hypocalcemia, leading to tetany. Therefore, checking magnesium levels in addition to calcium is crucial for accurately diagnosing the cause of tetany.

The other options are incorrect:

• Vitamin: This is too broad a category and doesn’t specify a particular vitamin relevant to calcium or magnesium metabolism.
• Phosphate: While related to calcium metabolism, it’s less likely to be the direct cause of tetany compared to magnesium.
• Sodium: Primarily involved in fluid balance and nerve conduction, but not specifically related to muscle cramps or spasms.

Answer: Calcium and phosphate

Calcium and phosphate have a reciprocal relationship, meaning that when one level increases, the other tends to decrease, and vice versa. This relationship is primarily regulated by parathyroid hormone (PTH).

The other options are incorrect:

• Calcium and magnesium: Both are important electrolytes, but they don’t have a consistent reciprocal relationship like calcium and phosphate.
• Sodium and potassium: While these electrolytes are essential and interact, they don’t have a direct reciprocal relationship like calcium and phosphate.
• Chloride and CO2: These are related to acid-base balance but not directly linked in a reciprocal manner.

Answer: Parathyroid glands

The parathyroid glands play a pivotal role in regulating serum phosphate levels. Parathyroid hormone (PTH) increases phosphate excretion by the kidneys, thus indirectly controlling its serum concentration.

The other options are incorrect:

• Small intestine: Primarily involved in absorption of nutrients, including phosphate, but not its primary regulator.
• Pancreas: Primarily involved in glucose metabolism.
• Skeleton: Serves as a storage site for calcium and phosphate but is not the primary regulator of serum phosphate levels.

Answer: Patients who are receiving carbohydrate hyperalimentation

Carbohydrate hyperalimentation, which is the administration of concentrated glucose solutions intravenously, can lead to a decrease in serum phosphorus levels. This is because insulin, released in response to the glucose infusion, promotes the movement of phosphorus into the cells.

The other options are incorrect:

• Patients with pituitary tumors: Not directly linked to significant changes in serum phosphorus levels.
• Chronic renal disease: Typically associated with hyperphosphatemia (increased phosphorus levels).
• Hypoparathyroidism: Often leads to hypocalcemia and hyperphosphatemia.

Answer: Maintain colloidal osmotic pressure

Albumin is the primary protein responsible for maintaining the osmotic pressure within blood vessels. This pressure prevents fluid from leaking out into the surrounding tissues.

The other options are incorrect:

• Maintain blood viscosity: While albumin contributes to blood viscosity, its primary role is in maintaining osmotic pressure.
• Increase antibody production: This is the function of immunoglobulins, not albumin.
• Increase fibrinogen formation: Fibrinogen is involved in blood clotting, not related to albumin’s function.

Answer: Measure the total volume

To accurately quantify the amount of protein in a 24-hour urine specimen, it is essential to know the total volume collected. This volume is used to calculate the protein concentration per unit volume.

The other options are incorrect:

• Screen for albumin using a dipstick: This is a qualitative test, not suitable for quantitative protein measurement.
• Subculture the urine for bacteria: This is unnecessary for a quantitative protein analysis and would introduce additional steps and potential errors.
• Add the appropriate preservative: Preservatives are typically added after measuring the total volume to prevent bacterial growth and protein degradation during the analysis.

Answer: Transferrin

Total Iron Binding Capacity (TIBC) measures the amount of transferrin available in the blood to bind with iron. Transferrin is a protein specifically designed to transport iron in the bloodstream.

The other options are incorrect:

• Ferritin: Primarily a storage protein for iron, not its transport.
• Hemoglobin: Primarily responsible for oxygen transport, not iron transport.
• Ceruloplasmin: Primarily involved in copper metabolism, not iron transport.

Answer: Separation of iron from transferring

To accurately measure serum iron, it is necessary to first release the iron bound to transferrin. This is typically achieved through acidification or reduction of the sample.

The other options are incorrect:

• Free iron precipitation: Free iron is not typically precipitated in the initial step of serum iron determination.
• Direct reaction with appropriate chromagen: This would occur after the iron is released from transferrin.
• Iron saturation of transferrin: This is a calculation based on serum iron and TIBC results, not a step in the measurement process.

Answer: Renal functional impairment

The Jaffe reaction is a chemical method used to measure creatinine levels in serum. Creatinine is a waste product produced by muscle metabolism and is primarily eliminated by the kidneys. Elevated creatinine levels indicate impaired kidney function.

The other options are incorrect:

Arrhythmia: A heart rhythm disorder unrelated to kidney function or creatinine levels.

Prolonged hypothermia: Not directly related to creatinine levels.

Pregnancy: Can affect various biochemical parameters but not specifically creatinine.

Answer: Glomerular filtration rate

Creatinine clearance is a measure of how efficiently the kidneys are filtering waste products from the blood. The glomerular filtration rate (GFR) is the volume of fluid filtered from the blood by the kidneys per unit time. By measuring the amount of creatinine excreted in the urine compared to the blood level, we can estimate the GFR, which is a good indicator of overall kidney function.

The other options are incorrect:

• Renal glomerular and tubular mass: Creatinine clearance does not directly measure the physical mass of the kidney but rather its functional capacity.
• Tubular secretion of creatinine: While some creatinine is secreted by the tubules, the primary mechanism for its elimination is glomerular filtration.
• Glomerular secretion of creatinine: Creatinine is filtered, not secreted, by the glomerulus.

Answer: Ceruloplasmin

Approximately 90% of the copper in the blood is bound to ceruloplasmin. Ceruloplasmin is a copper-containing protein that plays a crucial role in copper transport and metabolism in the body.

The other options are incorrect:

• Transferrin: Primarily carries iron.
• Albumin: Primarily maintains osmotic pressure and transports various substances, but not predominantly copper.
• Cryoglobulin: Abnormal proteins that precipitate at cold temperatures, unrelated to copper transport.

Answer: Electrophoresis on a diffirent medium and acidic pH

Hemoglobin S and D have similar migration patterns on standard alkaline electrophoresis, making them difficult to differentiate. However, by using a different medium and an acidic pH, their electrophoretic mobility changes, allowing for clear separation and identification.

The other options are incorrect:

• Kleihauer-Betke acid elution: Used to detect fetal hemoglobin, not for differentiating adult hemoglobin variants.
• Hemoglobin A2 quantitation: Measures the level of hemoglobin A2, not used to differentiate between S and D.
• Electrophoresis at higher voltage: Increasing voltage might improve resolution but doesn’t change the migration pattern of S and D in alkaline conditions.

Answer: Electron acceptors

Cytochromes are proteins involved in the electron transport chain. Their primary function is to accept electrons from one molecule and transfer them to another in a series of redox reactions. This process is crucial for energy production within cells.

The other options are incorrect:

• Protein acceptors: Cytochromes are proteins themselves, and they do not accept other proteins in their function.
• Oxygen acceptors: While oxygen is the final electron acceptor in the electron transport chain, cytochromes themselves are intermediate electron carriers.
• ATP acceptors: ATP is produced as a result of the electron transport chain, but cytochromes do not directly accept ATP.

Answer: Brown algae

Alginic acid is a polysaccharide found in the cell walls of brown algae. It provides structural support and also has commercial applications as a thickener and stabilizer.

The other options are incorrect:

• Red and brown algae: Incorrect as alginic acid is specifically derived from brown
• Red algae: Known for producing agar and carrageenan, not alginic acid.
• Green algae: While they have cell walls, they do not produce alginic acid.

Answer: Lecithinase

Naggler’s reaction is used to detect lecithinase activity, particularly in certain bacteria like Clostridium perfringens. Lecithinase is an enzyme that breaks down lecithin, a component of cell membranes.

The other options are incorrect:

• None of the above: Incorrect as the correct answer is lecithinase.
• Coagulase: An enzyme that clots plasma.
• Hyaluronidase: An enzyme that breaks down hyaluronic acid.