Welcome to Part 49 of the ASCP MLS Exam Practice Series, focusing on Lipids, Lipoproteins, and Cholesterol Metabolism. Lipids are vital biological molecules that play key roles in energy storage, cell membrane structure, and hormone synthesis. This section explores the chemistry of lipids, their metabolism, clinical testing methods, and interpretation of lipid disorders that impact cardiovascular health.
📘 Key Topics Covered
- Classification and chemical structure of lipids (fatty acids, triglycerides, phospholipids, sterols)
- Lipoprotein types and functions (chylomicrons, VLDL, LDL, HDL)
- Lipid transport and metabolism
- Cholesterol synthesis and regulation
- Atherosclerosis and dyslipidemia
- Laboratory analysis of triglycerides, cholesterol, and HDL/LDL
- Enzymatic and precipitation methods for lipid testing
- Interpretation of lipid profile and cardiovascular risk assessment
🧠 Learning Objectives
By the end of this part, you should be able to:
- Classify major lipids and describe their biological functions.
- Explain lipid and lipoprotein metabolism pathways.
- Interpret lipid profile test results and identify common disorders.
- Relate lipid abnormalities to cardiovascular risk and clinical significance.
60 MCQs (3881 – 3940):
- High levels of which lipoprotein class are associated with a decreased risk of accelerated atherosclerosis?
a) Chylomicrons
b) VLDL
c) LDL
d) HDL - The chemical composition of HDL is characterized by a high percentage of:
a) Triglyceride 60%, Cholesterol 15%
b) Triglyceride 10%, Cholesterol 45%
c) Triglyceride 5%, Cholesterol 15%, Protein 50%
d) Triglyceride 85%, Cholesterol 5% - In familial hypercholesterolemia, the hallmark laboratory finding is a primary elevation of:
a) Chylomicrons
b) Low-Density Lipoproteins (LDL)
c) High-Density Lipoproteins (HDL)
d) Apolipoprotein A₁ - The lipoprotein that transports cholesterol away from peripheral tissues back to the liver is:
a) Chylomicrons
b) VLDL
c) LDL
d) HDL - A fasting serum sample from a patient appears milky. After overnight refrigeration, a thick creamy layer forms over a turbid infranatant. This description is most consistent with:
a) Isolated HDL deficiency
b) An elevation of LDL alone
c) An elevation of both chylomicrons and VLDL
d) An elevation of HDL alone - The Friedewald formula is used to calculate LDL cholesterol. Which two measurements must be performed by the same chemical procedure for an accurate calculation?
a) Total Cholesterol and Triglyceride
b) Total Cholesterol and HDL Cholesterol
c) Triglyceride and Chylomicrons
d) Apolipoprotein A and Apolipoprotein B - The primary function of Very-Low-Density Lipoproteins (VLDL) is to transport:
a) Cholesterol from peripheral cells to the liver
b) Exogenous dietary triglycerides
c) Endogenous triglycerides from the liver
d) Phospholipids to cell membranes - A deficiency in which of the following is associated with the accumulation of chylomicrons in the blood?
a) Lecithin-Cholesterol Acyltransferase (LCAT)
b) Hepatic Lipase
c) Lipoprotein Lipase
d) Apolipoprotein B-100 - Which of the following lipid results would be most significantly and directly elevated on a serum specimen from a non-fasting patient?
a) Total Cholesterol
b) Triglyceride
c) HDL Cholesterol
d) LDL Cholesterol (calculated) - Tangier disease results from a familial absence or severe deficiency of which lipoprotein?
a) Chylomicrons
b) LDL
c) VLDL
d) HDL - Which apolipoprotein is the major structural component of HDL and acts as a cofactor for LCAT?
a) Apo B-100
b) Apo B-48
c) Apo A-I
d) Apo E - A serum specimen that appears turbid suggests a significant elevation of:
a) Cholesterol
b) Albumin
c) Chylomicrons or VLDL
d) Free Fatty Acids - The majority (60-75%) of the total plasma cholesterol is carried by which lipoprotein?
a) Chylomicrons
b) VLDL
c) LDL
d) HDL - A 1-year-old patient with a genetic lipoprotein lipase deficiency would most likely have a lipid profile showing:
a) Isolated high LDL cholesterol
b) Markedly elevated triglycerides and visible chylomicrons
c) Isolated low HDL cholesterol
d) Elevated VLDL with normal chylomicrons - Which of the following is the best course of action for a lipemic serum sample that has been frozen and is being prepared for a triglyceride assay?
a) Warm to 37°C and mix thoroughly before analysis.
b) Warm to 15°C and centrifuge to remove the fat layer.
c) Discard it, as freezing destroys triglycerides.
d) Extract the lipids with an organic solvent first. - Premature atherosclerosis is most directly associated with elevated levels of:
a) Chylomicrons
b) High-Density Lipoproteins (HDL)
c) Low-Density Lipoproteins (LDL)
d) Apolipoprotein A-I - The most common cause of analytical error in the routine precipitation method for HDL cholesterol measurement is:
a) Inaccurate protein estimation of HDL
b) Coprecipitation of HDL with LDL
c) Incomplete precipitation of apoB-containing lipoproteins
d) A small concentration of apoB-containing lipoproteins after precipitation - Apolipoprotein B-100 is a major component of which lipoprotein?
a) Chylomicrons
b) HDL
c) LDL
d) VLDL and LDL - A patient’s lipid results 6 hours postprandial are: Triglycerides 260 mg/dL and Cholesterol 120 mg/dL. The best interpretation is that:
a) Both results are normal and unaffected by the meal.
b) Cholesterol is normal, but triglycerides are elevated, likely due to the recent meal.
c) Both results are elevated, indicating a metabolic problem.
d) Both results are low, indicating a metabolic problem. - Which lipoprotein is responsible for transporting exogenous (dietary) triglycerides?
a) VLDL
b) LDL
c) HDL
d) Chylomicrons - For which of the following tests is a strict 12-14 hour fast most critical to ensure an accurate result?
a) Serum Sodium
b) Triglycerides
c) Total Cholesterol
d) Lactate Dehydrogenase (LD) - In most enzymatic methods for quantifying serum triglycerides, the substance that is actually measured is:
a) Fatty Acids
b) Glycerol
c) Phospholipids
d) Pre-beta Lipoprotein - Which of the following methods is most suited for the high-volume clinical laboratory measurement of HDL cholesterol?
a) Ultracentrifugation
b) Agarose Gel Electrophoresis
c) Homogeneous (Direct) Assay
d) Column Chromatography - The “Reverse Cholesterol Transport” pathway is primarily mediated by:
a) Chylomicrons
b) VLDL
c) LDL
d) HDL - A serum sample from a patient with a history of recurrent abdominal pain is found to be lipemic. Electrophoresis shows a prominent chylomicron band. This finding is most consistent with a type of hyperlipoproteinemia caused by a deficiency in:
a) LDL Receptor
b) Lipoprotein Lipase
c) Apo A-I Synthesis
d) Hepatic Triglyceride Lipase - Which lipoprotein particle has the lowest density?
a) HDL
b) LDL
c) VLDL
d) Chylomicrons - In the endogenous lipid pathway, the liver synthesizes and secretes which triglyceride-rich lipoprotein?
a) Chylomicrons
b) VLDL
c) IDL
d) LDL - A patient has the following lipid profile: Total Cholesterol 300 mg/dL, LDL Increased, HDL Decreased, Triglycerides 1200 mg/dL, Chylomicrons present. How would the serum most likely appear after overnight refrigeration?
a) Clear
b) Uniformly cloudy
c) Creamy layer over cloudy serum
d) Creamy layer over clear serum - Which of the following is a major risk factor for the development of atherosclerosis?
a) Elevated HDL cholesterol
b) Elevated LDL cholesterol
c) Low total cholesterol
d) Elevated Apo A-I - The most consistent source of error in the indirect (precipitation) method for HDL cholesterol is:
a) Incomplete precipitation of LDL and VLDL
b) Over-precipitation of HDL
c) Hemolysis of the sample
d) Interference from high triglycerides - Which of the following is the basic structural unit of lipids?
a) Amino acid
b) Fatty acid
c) Monosaccharide
d) Nucleotide - The main function of lipids in the human body is to:
a) Provide structural support only
b) Store energy and form cell membranes
c) Regulate enzyme activity
d) Produce urea - Triglycerides are composed of:
a) Glycerol and three fatty acids
b) Glycerol and one phosphate group
c) Three glucose molecules
d) Two fatty acids and one amino group - The process of lipid breakdown is known as:
a) Lipogenesis
b) Lipolysis
c) Lipoxidation
d) Lipoprotein synthesis - Which of the following is the major site of fatty acid synthesis?
a) Kidney
b) Liver
c) Brain
d) Muscle - The transport form of dietary lipids in plasma is:
a) LDL
b) HDL
c) Chylomicrons
d) VLDL - The enzyme lipoprotein lipase primarily acts on:
a) Chylomicrons and VLDL
b) LDL only
c) HDL only
d) Free fatty acids - Which lipoprotein carries cholesterol from tissues to the liver?
a) VLDL
b) LDL
c) HDL
d) IDL - Which lipoprotein is often referred to as “bad cholesterol”?
a) HDL
b) LDL
c) VLDL
d) Chylomicron - The main function of HDL is to:
a) Deliver triglycerides to cells
b) Carry cholesterol to tissues
c) Remove cholesterol from tissues for excretion
d) Transport fatty acids to mitochondria - Cholesterol serves as a precursor for:
a) Bile acids, vitamin D, and steroid hormones
b) Amino acids
c) Glucose
d) Fatty acids - The first step in cholesterol synthesis occurs in the:
a) Cytoplasm
b) Mitochondria
c) Nucleus
d) Lysosomes - The rate-limiting enzyme in cholesterol synthesis is:
a) HMG-CoA reductase
b) Acetyl-CoA carboxylase
c) Lipase
d) G6PD - Bile acids are synthesized from:
a) Glucose
b) Cholesterol
c) Triglycerides
d) Phospholipids - The lipoprotein with the highest protein content is:
a) HDL
b) LDL
c) VLDL
d) Chylomicron - Which lipid is a major component of cell membranes?
a) Triglycerides
b) Phospholipids
c) Steroids
d) Waxes - The enzyme responsible for hydrolysis of triglycerides in adipose tissue is:
a) Lipoprotein lipase
b) Hormone-sensitive lipase
c) Pancreatic lipase
d) Lecithin-cholesterol acyltransferase - Which hormone stimulates lipolysis?
a) Insulin
b) Glucagon
c) Thyroxine
d) Oxytocin - A deficiency of lipoprotein lipase leads to:
a) Hypertriglyceridemia
b) Hypoglycemia
c) Hypercholesterolemia
d) Ketosis - Ketone bodies are formed from:
a) Glucose
b) Amino acids
c) Fatty acids
d) Cholesterol - The major ketone bodies include all except:
a) Acetone
b) Acetoacetate
c) Beta-hydroxybutyrate
d) Pyruvate - In lipid metabolism, carnitine is required for:
a) Transport of fatty acids into mitochondria
b) Synthesis of triglycerides
c) Cholesterol esterification
d) Lipoprotein assembly - Phospholipids differ from triglycerides in that they contain:
a) A nitrogen base and a phosphate group
b) Three fatty acids
c) Only one fatty acid
d) A carbohydrate chain - Which of the following enzymes esterifies cholesterol?
a) Lipase
b) Lecithin-cholesterol acyltransferase (LCAT)
c) Acetyl-CoA carboxylase
d) HMG-CoA reductase - The “clearance factor” for removing triglycerides from plasma is:
a) HDL
b) LDL
c) Lipoprotein lipase
d) Acetyl-CoA - Increased LDL levels are associated with:
a) Decreased risk of atherosclerosis
b) Increased risk of atherosclerosis
c) Decreased cholesterol synthesis
d) Increased HDL formation - Tangier disease is characterized by a deficiency of:
a) HDL
b) LDL
c) VLDL
d) Apo B-100 - The Friedewald formula estimates LDL cholesterol using:
a) HDL, triglycerides, and total cholesterol
b) HDL and total protein
c) HDL and glucose
d) Total cholesterol and calcium - The lipoprotein electrophoresis pattern that migrates closest to the origin is:
a) HDL
b) LDL
c) VLDL
d) Chylomicron - Atherosclerosis results primarily from:
a) High HDL and low LDL
b) Low triglyceride levels
c) High LDL and low HDL levels
d) Increased bile acid production
📌 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) HDL
- c) Triglyceride 5%, Cholesterol 15%, Protein 50%
- b) Low-Density Lipoproteins (LDL)
- d) HDL
- c) An elevation of both chylomicrons and VLDL
- a) Total Cholesterol and Triglyceride
- c) Endogenous triglycerides from the liver
- c) Lipoprotein Lipase
- b) Triglyceride
- d) HDL
- c) Apo A-I
- c) Chylomicrons or VLDL
- c) LDL
- b) Markedly elevated triglycerides and visible chylomicrons
- a) Warm to 37°C and mix thoroughly before analysis.
- c) Low-Density Lipoproteins (LDL)
- c) Incomplete precipitation of apoB-containing lipoproteins
- d) VLDL and LDL
- b) Cholesterol is normal, but triglycerides are elevated, likely due to the recent meal.
- d) Chylomicrons
- b) Triglycerides
- b) Glycerol
- c) Homogeneous (Direct) Assay
- d) HDL
- b) Lipoprotein Lipase
- d) Chylomicrons
- b) VLDL
- c) Creamy layer over cloudy serum
- b) Elevated LDL cholesterol
- a) Incomplete precipitation of LDL and VLDL
- b) Fatty acid
- b) Store energy and form cell membranes
- a) Glycerol and three fatty acids
- b) Lipolysis
- b) Liver
- c) Chylomicrons
- a) Chylomicrons and VLDL
- c) HDL
- b) LDL
- c) Remove cholesterol from tissues for excretion
- a) Bile acids, vitamin D, and steroid hormones
- a) Cytoplasm
- a) HMG-CoA reductase
- b) Cholesterol
- a) HDL
- b) Phospholipids
- b) Hormone-sensitive lipase
- b) Glucagon
- a) Hypertriglyceridemia
- c) Fatty acids
- d) Pyruvate
- a) Transport of fatty acids into mitochondria
- a) A nitrogen base and a phosphate group
- b) Lecithin-cholesterol acyltransferase (LCAT)
- c) Lipoprotein lipase
- b) Increased risk of atherosclerosis
- a) HDL
- a) HDL, triglycerides, and total cholesterol
- d) Chylomicron
- c) High LDL and low HDL levels
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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