Welcome to Part 51 of the ASCP MLS Exam Practice Series, covering Vitamins, Minerals, and Electrolyte Balance. Vitamins and minerals play essential roles in metabolism, enzyme activation, and physiological stability, while electrolytes are critical for maintaining fluid balance, nerve conduction, and acid-base equilibrium. This section highlights the biochemistry, clinical significance, and laboratory evaluation of these vital components.
📘 Key Topics Covered
- Classification of vitamins: water-soluble (B-complex, C) and fat-soluble (A, D, E, K)
- Functions, sources, and deficiency diseases of major vitamins
- Clinical testing for vitamin status (serum/plasma levels)
- Major minerals: calcium, phosphorus, magnesium, sodium, potassium, chloride
- Trace elements: iron, zinc, copper, selenium
- Role of electrolytes in homeostasis and osmoregulation
- Acid-base balance and anion gap overview
- Laboratory methods for electrolyte measurement (ion-selective electrodes, flame photometry)
- Clinical interpretation in dehydration, renal failure, and metabolic disorders
🧠 Learning Objectives
By the end of this part, you should be able to:
- Differentiate between fat- and water-soluble vitamins and their functions.
- Explain the clinical significance of essential minerals and trace elements.
- Interpret electrolyte results and recognize imbalances.
- Relate biochemical findings to disease conditions and nutritional status.
60 MCQs (4001-4060):
- Which of the following electrolytes is the chief plasma cation whose main function is maintaining osmotic pressure?
a) Chloride
b) Calcium
c) Potassium
d) Sodium - The solute that contributes the most to the total serum osmolality is:
a) Glucose
b) Urea
c) Chloride
d) Sodium - A reciprocal relationship exists between the serum concentrations of:
a) Sodium and Potassium
b) Calcium and Phosphate
c) Chloride and Bicarbonate
d) Calcium and Magnesium - The regulation of calcium and phosphorus metabolism is primarily accomplished by which gland?
a) Thyroid
b) Parathyroid
c) Adrenal Glands
d) Pituitary - Which percentage of total serum calcium is bound to protein (primarily albumin) and is thus nondiffusible?
a) 10-30%
b) 40-50%
c) 51-60%
d) 80-90% - A hospitalized patient experiences tetany (increased neuromuscular irritability). Which test should be ordered immediately?
a) Phosphate
b) BUN
c) Glucose
d) Calcium - The most accurate method for measuring ionized calcium involves the use of a(n):
a) Colorimetric assay with o-cresolphthalein complexone
b) Ion-selective electrode
c) Atomic absorption spectrophotometer
d) Fluorometric assay - A low concentration of serum phosphorus is commonly found in:
a) Chronic renal disease
b) Hypoparathyroidism
c) Patients receiving carbohydrate hyperalimentation
d) Patients with pituitary tumors - In an atomic absorption method for calcium determination, lanthanum is added to the reagent to:
a) Act as an internal standard
b) Bind calcium for detection
c) Eliminate protein interference
d) Prevent phosphate interference - Total Iron-Binding Capacity (TIBC) is a measure of the serum iron transporting capacity of:
a) Hemoglobin
b) Ceruloplasmin
c) Transferrin
d) Ferritin - A patient’s laboratory results show: low serum iron and low TIBC. This pattern is most consistent with:
a) Iron Deficiency Anemia
b) Anemia of Chronic Disease
c) Hemochromatosis
d) Thalassemia - Which of the following findings is characteristic of iron deficiency anemia?
a) Low serum iron, High TIBC
b) High serum iron, Low TIBC
c) Low serum iron, Low TIBC
d) High serum iron, High TIBC - A patient has a serum iron of 250 µg/dL and a TIBC of 250 µg/dL. These results are most indicative of:
a) Normal iron status
b) Iron deficiency anemia
c) Anemia of chronic disease
d) Iron overload (Hemochromatosis) - Wilson’s disease, characterized by abnormal copper accumulation, is associated with:
a) Increased serum copper and decreased urine copper
b) Decreased serum copper and increased urine copper
c) Increased serum ceruloplasmin
d) Decreased urine copper - Approximately 90% of the copper present in the blood is bound to:
a) Transferrin
b) Albumin
c) Ceruloplasmin
d) Cryoglobulin - A sweat chloride result of 55 mEq/L on a patient with respiratory problems is best interpreted as:
a) Normal
b) Abnormal, diagnostic of Cystic Fibrosis
c) Intermediate, requiring further testing
d) Invalid due to low sodium level - A potassium level of 6.8 mEq/L is obtained. Before reporting, the technologist should first:
a) Rerun the test on the same specimen
b) Check the serum for hemolysis
c) Check the age of the patient
d) Report the result immediately - Sodium determination by an indirect ion-selective electrode can be falsely decreased by:
a) Elevated chloride levels
b) Elevated lipid levels
c) Decreased protein levels
d) Decreased albumin levels - The “anion gap” is most useful as a quality control check for which set of electrolytes?
a) Calcium, Phosphorus, Magnesium
b) Sodium, Potassium, Chloride, Bicarbonate
c) AST, ALT, LD, Amylase
d) BUN, Creatinine, Uric Acid - The osmolal gap is defined as the difference between:
a) The ideal and real osmolality values
b) Calculated and measured osmolality values
c) Plasma and water osmolality values
d) Urine and serum osmolality values - A deficiency of which vitamin leads to night blindness?
a) Vitamin A
b) Vitamin C
c) Niacin
d) Thiamine - Pernicious anemia is associated with a deficiency of:
a) Vitamin A
b) Vitamin B12
c) Niacin
d) Thiamine - Rickets in children is associated with a deficiency of which vitamin?
a) Vitamin B1
b) Vitamin C
c) Niacin
d) Vitamin D - Pellagra, characterized by dermatitis, diarrhea, and dementia, is caused by a deficiency of:
a) Vitamin A
b) Vitamin B1 (Thiamine)
c) Niacin
d) Vitamin C - Which of the following vitamins is water-soluble?
a) Vitamin A
b) Vitamin C
c) Vitamin D
d) Vitamin K - Assay of transketolase activity in red blood cells is used to detect a deficiency of:
a) Thiamine
b) Folic Acid
c) Ascorbic Acid
d) Riboflavin - Serum concentrations of vitamin B12 are typically elevated in:
a) Pernicious anemia in relapse
b) Patients on chronic hemodialysis
c) Chronic granulocytic leukemia
d) Hodgkin disease - Absorption of dietary vitamin B12 requires the presence of:
a) Gastrin
b) Intrinsic Factor
c) Secretin
d) Folic Acid - Which of the following is the biologically active precursor of Vitamin A?
a) Biotin
b) Retinol
c) Folic Acid
d) Ascorbic Acid - Magnesium carbonate is added during the determination of Total Iron-Binding Capacity (TIBC) in order to:
a) Allow the color to develop
b) Precipitate protein
c) Bind with hemoglobin iron
d) Remove excess unbound iron - Vitamins are best described as:
a) Energy-producing nutrients
b) Organic compounds required in small amounts for metabolism
c) Inorganic elements needed for enzyme function
d) Nonessential dietary components - Which of the following is a fat-soluble vitamin?
a) Vitamin C
b) Vitamin B12
c) Vitamin A
d) Folic acid - Which of the following is a water-soluble vitamin?
a) Vitamin D
b) Vitamin K
c) Vitamin E
d) Vitamin C - The major function of Vitamin A is related to:
a) Vision and epithelial tissue maintenance
b) Collagen synthesis
c) Blood coagulation
d) Calcium absorption - Vitamin D is essential for:
a) Wound healing
b) Calcium and phosphate metabolism
c) Collagen formation
d) Red blood cell production - Vitamin E primarily functions as a:
a) Coenzyme in oxidation-reduction reactions
b) Hormone precursor
c) Fat-soluble antioxidant
d) Hemoglobin stabilizer - Vitamin K is required for the synthesis of:
a) Hemoglobin
b) Clotting factors II, VII, IX, and X
c) Albumin
d) Collagen - Which vitamin deficiency causes scurvy?
a) Vitamin D
b) Vitamin C
c) Vitamin A
d) Vitamin K - Pellagra is caused by a deficiency of:
a) Thiamine
b) Niacin
c) Riboflavin
d) Biotin - Beriberi is due to a deficiency of:
a) Vitamin C
b) Vitamin B1 (Thiamine)
c) Vitamin B6 (Pyridoxine)
d) Vitamin B12 - Pernicious anemia results from deficiency of:
a) Vitamin B12
b) Vitamin D
c) Vitamin A
d) Folic acid - Megaloblastic anemia is commonly caused by a deficiency of:
a) Folic acid and Vitamin B12
b) Thiamine
c) Riboflavin
d) Vitamin K - The most abundant mineral in the human body is:
a) Iron
b) Sodium
c) Calcium
d) Potassium - Calcium homeostasis is regulated by:
a) Insulin and glucagon
b) Parathyroid hormone and Vitamin D
c) Aldosterone and cortisol
d) Epinephrine - Iron in the blood is primarily bound to:
a) Albumin
b) Hemoglobin
c) Transferrin
d) Ferritin - The trace element essential for thyroid hormone synthesis is:
a) Zinc
b) Iodine
c) Copper
d) Manganese - Which of the following minerals is a component of hemoglobin?
a) Zinc
b) Copper
c) Iron
d) Calcium - Magnesium plays a key role in:
a) Protein synthesis only
b) DNA stability and enzyme activity
c) Bone resorption
d) Bile acid metabolism - The major intracellular cation in the body is:
a) Sodium
b) Calcium
c) Potassium
d) Chloride - The major extracellular cation is:
a) Sodium
b) Potassium
c) Magnesium
d) Hydrogen - The principal extracellular anion is:
a) Bicarbonate
b) Chloride
c) Sulfate
d) Phosphate - Hyponatremia refers to:
a) Low blood potassium
b) Low blood sodium
c) Low blood chloride
d) Low blood calcium - Hyperkalemia refers to:
a) Increased potassium in the blood
b) Decreased calcium in the blood
c) Increased sodium in the blood
d) Low chloride concentration - The anion gap is primarily used to evaluate:
a) Kidney function
b) Acid-base balance
c) Liver enzyme activity
d) Oxygen transport - The normal reference range for serum sodium is approximately:
a) 90–110 mmol/L
b) 135–145 mmol/L
c) 120–130 mmol/L
d) 150–160 mmol/L - The normal reference range for serum potassium is approximately:
a) 2.0–3.0 mmol/L
b) 3.5–5.0 mmol/L
c) 6.0–8.0 mmol/L
d) 8.0–10.0 mmol/L - Which electrolyte imbalance is most likely associated with cardiac arrhythmia?
a) Hypokalemia
b) Hypernatremia
c) Hypochloremia
d) Hypercalcemia - A decreased serum calcium level is known as:
a) Hypercalcemia
b) Hypocalcemia
c) Hypokalemia
d) Hyponatremia - A decreased serum phosphate concentration may indicate:
a) Vitamin D deficiency
b) Renal failure
c) Acidosis
d) Hypoparathyroidism - The main buffer system that maintains blood pH is the:
a) Phosphate buffer
b) Hemoglobin buffer
c) Bicarbonate-carbonic acid buffer
d) Protein buffer
📌 How to Use This Practice Set
- Answer each question before checking the key.
- Focus on why the correct answer is right and the others are wrong.
- Use this set as timed practice to simulate the real exam environment.
Answer Key
Answer Key:
- d) Sodium
- d) Sodium
- b) Calcium and Phosphate
- b) Parathyroid
- b) 40-50%
- d) Calcium
- b) Ion-selective electrode
- c) Patients receiving carbohydrate hyperalimentation
- d) Prevent phosphate interference
- c) Transferrin
- b) Anemia of Chronic Disease
- a) Low serum iron, High TIBC
- d) Iron overload (Hemochromatosis)
- b) Decreased serum copper and increased urine copper
- c) Ceruloplasmin
- c) Intermediate, requiring further testing
- b) Check the serum for hemolysis
- b) Elevated lipid levels
- b) Sodium, Potassium, Chloride, Bicarbonate
- b) Calculated and measured osmolality values
- a) Vitamin A
- b) Vitamin B12
- d) Vitamin D
- c) Niacin
- b) Vitamin C
- a) Thiamine
- c) Chronic granulocytic leukemia
- b) Intrinsic Factor
- b) Retinol
- d) Remove excess unbound iron
- b) Organic compounds required in small amounts for metabolism
- c) Vitamin A
- d) Vitamin C
- a) Vision and epithelial tissue maintenance
- b) Calcium and phosphate metabolism
- c) Fat-soluble antioxidant
- b) Clotting factors II, VII, IX, and X
- b) Vitamin C
- b) Niacin
- b) Vitamin B1 (Thiamine)
- a) Vitamin B12
- a) Folic acid and Vitamin B12
- c) Calcium
- b) Parathyroid hormone and Vitamin D
- c) Transferrin
- b) Iodine
- c) Iron
- b) DNA stability and enzyme activity
- c) Potassium
- a) Sodium
- b) Chloride
- b) Low blood sodium
- a) Increased potassium in the blood
- b) Acid-base balance
- b) 135–145 mmol/L
- b) 3.5–5.0 mmol/L
- a) Hypokalemia
- b) Hypocalcemia
- a) Vitamin D deficiency
- c) Bicarbonate-carbonic acid buffer
Top 8 Medical Laboratory Scientist (MLS) Exams:
Top 8 Medical Laboratory Scientist (MLS) Exams that are recognized globally and can help professionals validate their credentials and enhance their career opportunities:
1. ASCP – American Society for Clinical Pathology (USA)
- Exam Name: MLS(ASCP)
- Eligibility: Bachelor’s degree with clinical laboratory experience.
- Global Recognition: High
- Purpose: Certifies Medical Laboratory Scientists in the United States and internationally.
2. AMT – American Medical Technologists (USA)
- Exam Name: MLT(AMT) or MT(AMT)
- Eligibility: Academic and/or work experience in medical laboratory technology.
- Global Recognition: Moderate
- Purpose: Credentialing for medical technologists and technicians.
3. AIMS – Australian Institute of Medical and Clinical Scientists
- Exam Name: AIMS Certification Exam
- Eligibility: Assessment of qualifications and work experience.
- Recognition: Required for practice in Australia.
- Purpose: Certification and registration in Australia.
4. CSMLS – Canadian Society for Medical Laboratory Science
- Exam Name: CSMLS General or Subject-specific Exams
- Eligibility: Graduation from a CSMLS-accredited program or equivalent.
- Recognition: Canada
- Purpose: Entry-to-practice certification in Canada.
5. IBMS – Institute of Biomedical Science (UK)
- Exam Name: Registration and Specialist Portfolio Assessment
- Eligibility: Accredited degree and lab experience.
- Recognition: UK and some Commonwealth countries.
- Purpose: Biomedical Scientist registration with the HCPC (UK).
6. HAAD / DOH – Department of Health, Abu Dhabi (UAE)
- Exam Name: DOH/HAAD License Exam
- Eligibility: Degree in medical laboratory science and experience.
- Recognition: UAE (Abu Dhabi)
- Purpose: Licensure for medical laboratory practice in Abu Dhabi.
7. DHA – Dubai Health Authority (UAE)
- Exam Name: DHA License Exam for Medical Laboratory Technologists
- Eligibility: Relevant degree and experience.
- Recognition: Dubai, UAE
- Purpose: Professional license for clinical laboratory practice in Dubai.
8. MOH – Ministry of Health (Gulf Countries like UAE, Saudi Arabia, Kuwait)
- Exam Name: MOH License Exam
- Eligibility: BSc/Diploma in Medical Laboratory + experience.
- Recognition: Varies by country.
- Purpose: Required for practicing in public and private sector labs.
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