Welcome to Part 48 of the ASCP MLS Exam Practice Series, dedicated to Proteins, Amino Acids, and Plasma Proteins. Proteins are fundamental to all biological systems — they serve as enzymes, transporters, structural components, and defense molecules. This section explores the chemistry, classification, and clinical applications of proteins and amino acids, with emphasis on laboratory techniques used to evaluate protein disorders such as nephrotic syndrome, liver disease, and multiple myeloma.
📘 Key Topics Covered
- Structure and classification of amino acids
- Peptide bond formation and levels of protein structure (primary → quaternary)
- Plasma proteins: albumin, globulins, fibrinogen
- Protein synthesis and degradation pathways
- Protein electrophoresis and interpretation of patterns
- Clinical significance of protein abnormalities
- Total protein and albumin measurement methods (Biuret, BCG, BCP)
- Bence Jones protein and monoclonal gammopathies
- CSF and urine protein testing
🧠 Learning Objectives
By the end of this part, you should be able to:
- Correlate protein abnormalities with clinical conditions and laboratory tests.
- Describe the structure and chemical properties of amino acids and proteins.
- Identify and explain the functions of major plasma proteins.
- Interpret protein electrophoresis and immunofixation results.
60 MCQs (3821-3880):
- What is the main function of serum albumin in the peripheral blood?
a) To increase antibody production
b) To maintain colloidal osmotic pressure
c) To increase fibrinogen formation
d) To maintain blood viscosity - The biuret reaction for the analysis of serum protein depends on the number of:
a) Free amino groups
b) Free carboxyl groups
c) Peptide bonds
d) Tyrosine residues - In a pleural effusion caused by Streptococcus pneumoniae, the ratio of pleural fluid protein to serum protein would likely be:
a) >0.6
b) >0.5
c) <0.3
d) <0.7 - Which of the following amino acids is associated with a sulfhydryl group?
a) Glycine
b) Serine
c) Cysteine
d) Tyrosine - A large decrease in the α₁ peak on a serum protein electrophoresis is most indicative of:
a) An acute phase reaction
b) Alpha-1 antitrypsin deficiency
c) Chronic inflammation
d) Nephrotic syndrome - The first step in analyzing a 24-hour urine specimen for quantitative urine protein is to:
a) Subculture the urine for bacteria
b) Add the appropriate preservative
c) Screen for albumin using a dipstick
d) Measure the total volume - The protein that has the highest dye-binding capacity with bromcresol green or purple is:
a) Alpha-1 globulin
b) Albumin
c) Beta globulin
d) Gamma globulin - Maple syrup urine disease is characterized by an increase in which of the following urinary amino acids?
a) Phenylalanine
b) Tyrosine
c) Valine, leucine, and isoleucine
d) Cystine and cysteine - In which of the following conditions would you expect to see an increased serum albumin concentration?
a) Nephrotic syndrome
b) Acute hepatitis
c) Chronic inflammation
d) Dehydration - The electrophoretic pattern of a plasma sample, compared to a serum sample, typically shows a:
a) Broad prealbumin peak
b) Sharp fibrinogen peak
c) Diffuse pattern because of anticoagulants
d) Decreased globulin fraction - The presence of C-reactive protein in the blood is a classic indicator of:
a) A recent streptococcal infection
b) Recovery from a pneumococcal infection
c) An inflammatory process
d) A state of hypersensitivity - Bence Jones proteins are best identified by which method?
a) Sulfosalicylic acid test
b) Urine reagent strips
c) Immunofixation electrophoresis
d) Biuret reaction - Which of the following serum protein fractions is most likely to be elevated in patients with nephrotic syndrome?
a) Alpha-1 globulin
b) Albumin
c) Alpha-2 globulin and beta globulin
d) Beta globulin and gamma globulin - The protein ceruloplasmin, which binds 90% of the copper in the blood, migrates in which region on serum protein electrophoresis?
a) Albumin
b) Alpha-1
c) Alpha-2
d) Beta - A patient with biliary cirrhosis would most likely show an elevation in which globulin fraction on serum protein electrophoresis?
a) Alpha-1
b) Alpha-2
c) Beta
d) Gamma - The end product of nitrogen metabolism and the principle excretory form of nitrogen is:
a) Amino Acids
b) Creatinine
c) Urea
d) Uric Acid - A serum protein electrophoresis pattern showing a “beta-gamma bridge” is most consistent with:
a) Acute inflammation
b) Hepatic cirrhosis
c) Nephrotic syndrome
d) Monoclonal gammopathy - Which of the following represents the end product of purine metabolism in humans?
a) AMP and GMP
b) DNA and RNA
c) Allantoin
d) Uric Acid - In a patient with glomerulonephritis, which of the following serum results would be most likely?
a) Creatinine decreased
b) Calcium increased
c) Phosphorous decreased
d) BUN increased - Serum haptoglobin is:
a) Decreased in patients with tissue injury and neoplasia
b) Increased in patients with prosthetic heart valves
c) Decreased in hemolytic anemia
d) Increased in in vitro hemolysis - A characteristic of Bence Jones protein that is used to distinguish it from other urinary proteins is its solubility:
a) In ammonium sulfate
b) In sulfuric acid
c) At 40-60°C
d) At 100°C - Analysis of CSF for oligoclonal bands is used to screen for which of the following disease states?
a) Multiple myeloma
b) Multiple sclerosis
c) Myasthenia gravis
d) von Willebrand disease - The C3 component of complement migrates with which globulin fraction on cellulose acetate electrophoresis at pH 8.6?
a) Albumin
b) Alpha-1
c) Alpha-2
d) Beta - Increased concentrations of alpha-fetoprotein (AFP) in adults are most characteristically associated with:
a) Hepatocellular carcinoma
b) Alcoholic cirrhosis
c) Chronic active hepatitis
d) Multiple myeloma - The recommended method for measuring total protein in serum is based on which reaction?
a) Molybdenum blue
b) Ferri-ferrocyanide
c) Resorcinol-HCl
d) Biuret - A patient has a serum protein electrophoresis showing a tall, narrow spike in the gamma region. This is most consistent with:
a) Cirrhosis
b) Acute inflammation
c) Monoclonal gammopathy
d) Polyclonal gammopathy - Which of the following determinations is useful in the prenatal diagnosis of open neural tube defects?
a) Amniotic fluid alpha-fetoprotein
b) Amniotic fluid estriol
c) Maternal serum estradiol
d) Maternal serum estrone - A urine albumin excretion rate of 50 µg/min (normal <20) correlates with the term:
a) Hematuria
b) Massive proteinuria
c) Microalbuminuria/albuminuria
d) Oliguria - Microalbuminuria/albuminuria is best determined by measuring urinary levels of:
a) Fructosamine
b) The ratio of albumin to creatinine
c) Pre-albumin
d) Beta-2 microglobulin - The troponin complex, a key marker for myocardial injury, consists of:
a) Troponin T, calcium, and tropomyosin
b) Troponin C, troponin I, and troponin T
c) Troponin I, actin, and tropomyosin
d) Troponin C, myoglobin, and actin - The basic building blocks of proteins are:
a) Monosaccharides
b) Amino acids
c) Fatty acids
d) Nucleotides - A peptide bond forms between which two groups?
a) Two amino groups
b) Two carboxyl groups
c) An amino and a carboxyl group
d) Two hydroxyl groups - Which of the following is an essential amino acid?
a) Glycine
b) Alanine
c) Leucine
d) Tyrosine - The secondary structure of a protein is stabilized primarily by:
a) Ionic bonds
b) Hydrogen bonds
c) Peptide bonds
d) Van der Waals forces - Which of the following represents a quaternary protein structure?
a) A single polypeptide chain
b) Alpha-helix
c) Multiple polypeptide chains joined together
d) Beta-turn - Denaturation of a protein involves:
a) Breaking peptide bonds
b) Loss of secondary and tertiary structure
c) Hydrolysis into amino acids
d) Conversion into nucleic acids - Albumin is primarily synthesized in the:
a) Pancreas
b) Liver
c) Kidney
d) Small intestine - The main function of plasma albumin is to:
a) Act as an enzyme
b) Maintain osmotic pressure and transport substances
c) Serve as an antibody
d) Facilitate blood coagulation - Which of the following plasma proteins functions in blood clotting?
a) Fibrinogen
b) Albumin
c) Transferrin
d) Haptoglobin - The normal reference range for total serum protein is approximately:
a) 2–4 g/dL
b) 4–6 g/dL
c) 6–8 g/dL
d) 8–10 g/dL - The Biuret method for total protein measurement is based on:
a) The binding of a dye to proteins
b) The presence of peptide bonds forming a violet color
c) The reaction of amino acids with ninhydrin
d) The reduction of copper ions - The bromocresol green (BCG) method is commonly used for measuring:
a) Total protein
b) Albumin
c) Globulins
d) Fibrinogen - Which of the following is a positive acute-phase reactant?
a) Albumin
b) Transferrin
c) C-reactive protein
d) Prealbumin - The electrophoretic fraction that migrates fastest toward the anode is:
a) Albumin
b) Alpha-1 globulin
c) Beta globulin
d) Gamma globulin - The most abundant plasma protein in normal human serum is:
a) Globulin
b) Albumin
c) Fibrinogen
d) Transferrin - A monoclonal spike (M-protein) on serum protein electrophoresis is characteristic of:
a) Liver disease
b) Multiple myeloma
c) Nephrotic syndrome
d) Acute inflammation - Bence Jones proteins are most often detected in:
a) Urine of multiple myeloma patients
b) Serum of diabetic patients
c) CSF of meningitis patients
d) Plasma of anemic patients - Which of the following proteins binds free hemoglobin in plasma?
a) Ceruloplasmin
b) Transferrin
c) Haptoglobin
d) Fibrinogen - The enzyme responsible for protein digestion in the stomach is:
a) Pepsin
b) Trypsin
c) Amylase
d) Lipase - The amino acid that contains sulfur in its side chain is:
a) Valine
b) Methionine
c) Alanine
d) Glycine - Immunoglobulins are classified under which protein fraction?
a) Alpha-globulins
b) Beta-globulins
c) Gamma-globulins
d) Albumin - Prealbumin is most useful in evaluating:
a) Chronic liver disease
b) Nutritional status and protein malnutrition
c) Kidney function
d) Hemolytic anemia - A decrease in serum albumin with an increase in alpha-2 globulins is typically seen in:
a) Nephrotic syndrome
b) Cirrhosis
c) Multiple myeloma
d) Inflammation - The Kjeldahl method measures protein concentration by determining:
a) Nitrogen content
b) Peptide bonds
c) Copper binding
d) Absorbance at 280 nm - Which amino acid is a precursor for serotonin?
a) Phenylalanine
b) Tryptophan
c) Tyrosine
d) Glycine - Which amino acid is most likely to absorb UV light at 280 nm?
a) Glycine
b) Tryptophan
c) Alanine
d) Serine - The main function of transferrin is to:
a) Transport copper
b) Transport iron
c) Carry oxygen
d) Bind bilirubin - Which protein transports copper in plasma?
a) Albumin
b) Ceruloplasmin
c) Haptoglobin
d) Transferrin - A decrease in total serum protein may occur in:
a) Dehydration
b) Nephrotic syndrome
c) Chronic infection
d) Multiple myeloma - The normal albumin to globulin (A/G) ratio in serum is approximately:
a) 0.5:1
b) 1.0:1
c) 1.2:1 to 2.0:1
d) 3.5:1
📌 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:
- b) To maintain colloidal osmotic pressure
- c) Peptide bonds
- a) >0.6
- c) Cysteine
- b) Alpha-1 antitrypsin deficiency
- d) Measure the total volume
- b) Albumin
- c) Valine, leucine, and isoleucine
- d) Dehydration
- b) Sharp fibrinogen peak
- c) At 40-60°C
- b) Multiple sclerosis
- d) Beta
- a) Hepatocellular carcinoma
- d) Biuret
- c) Monoclonal gammopathy
- a) Amniotic fluid alpha-fetoprotein
- c) Microalbuminuria/albuminuria
- b) The ratio of albumin to creatinine
- b) Troponin C, troponin I, and troponin T
- b) The presence of peptide bonds forming a violet color
- b) Albumin
- c) C-reactive protein
- a) Albumin
- b) Albumin
- b) Multiple myeloma
- a) Urine of multiple myeloma patients
- c) Haptoglobin
- a) Pepsin
- b) Methionine
- c) An inflammatory process
- c) Immunofixation electrophoresis
- c) Alpha-2 globulin and beta globulin
- c) Alpha-2
- d) Gamma
- c) Urea
- b) Hepatic cirrhosis
- d) Uric Acid
- d) BUN increased
- c) Decreased in hemolytic anemia
- b) Amino acids
- c) An amino and a carboxyl group
- c) Leucine
- b) Hydrogen bonds
- c) Multiple polypeptide chains joined together
- b) Loss of secondary and tertiary structure
- b) Liver
- b) Maintain osmotic pressure and transport substances
- a) Fibrinogen
- c) 6–8 g/dL
- c) Gamma-globulins
- b) Nutritional status and protein malnutrition
- a) Nephrotic syndrome
- a) Nitrogen content
- b) Tryptophan
- b) Tryptophan
- b) Transport iron
- b) Ceruloplasmin
- b) Nephrotic syndrome
- c) 1.2:1 to 2.0:1
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
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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.
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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.
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- Exam Name: DOH/HAAD License Exam
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7. DHA – Dubai Health Authority (UAE)
- Exam Name: DHA License Exam for Medical Laboratory Technologists
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8. MOH – Ministry of Health (Gulf Countries like UAE, Saudi Arabia, Kuwait)
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