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Questions and Answers
What is the primary carrier of cholesterol?
What is the primary carrier of cholesterol?
LDL
What kind of lipids are synthesized from acetyl coA?
What kind of lipids are synthesized from acetyl coA?
Chylomicrons have apoproteins B-48 mainly, and lesser amounts of A-I, C-I, C-II, and ____.
Chylomicrons have apoproteins B-48 mainly, and lesser amounts of A-I, C-I, C-II, and ____.
C-III
HDL is also known as 'bad cholesterol'.
HDL is also known as 'bad cholesterol'.
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What does HDL remove from peripheral tissues?
What does HDL remove from peripheral tissues?
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What is the primary purpose of the Adult Treatment Panel III Classification (ATP III)?
What is the primary purpose of the Adult Treatment Panel III Classification (ATP III)?
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Abnormal lipid metabolism is associated with a reduced risk of coronary heart disease.
Abnormal lipid metabolism is associated with a reduced risk of coronary heart disease.
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What is one recommendation regarding food intake for accurate cholesterol measurement?
What is one recommendation regarding food intake for accurate cholesterol measurement?
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What is used to remove all lipoproteins except HDL in the Precipitation Method for HDL-C estimation?
What is used to remove all lipoproteins except HDL in the Precipitation Method for HDL-C estimation?
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Match the cholesterol measurement method with its description:
Match the cholesterol measurement method with its description:
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What does the Ultracentrifugation method permit?
What does the Ultracentrifugation method permit?
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What appearance is indicative of Type I hyperlipoproteinemia?
What appearance is indicative of Type I hyperlipoproteinemia?
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Familial Combined Hyperlipidemia (FCHL) is the most common familial form of hyperlipidemia.
Familial Combined Hyperlipidemia (FCHL) is the most common familial form of hyperlipidemia.
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_______ is the major protein found in LDL and is associated with increased risk of coronary artery disease.
_______ is the major protein found in LDL and is associated with increased risk of coronary artery disease.
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Match the following lipid types with their characteristics:
Match the following lipid types with their characteristics:
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What is the purpose of converting blood ammonia to urea in the liver?
What is the purpose of converting blood ammonia to urea in the liver?
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Jaundice occurs when the liver is not able to remove the heme waste product called _________ from the blood.
Jaundice occurs when the liver is not able to remove the heme waste product called _________ from the blood.
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What does an elevated blood level of conjugated bilirubin indicate?
What does an elevated blood level of conjugated bilirubin indicate?
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Liver chemistry tests help diagnose or monitor liver disease.
Liver chemistry tests help diagnose or monitor liver disease.
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What does the measurement of AST and ALT levels indicate in liver diseases?
What does the measurement of AST and ALT levels indicate in liver diseases?
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Cholesterol level is an important factor in the process of _____________ disease.
Cholesterol level is an important factor in the process of _____________ disease.
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What enzyme is a good marker for extra hepatobiliary disorders such as biliary obstruction or cholestasis?
What enzyme is a good marker for extra hepatobiliary disorders such as biliary obstruction or cholestasis?
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What does ALP stand for in the context of cholesterol determination?
What does ALP stand for in the context of cholesterol determination?
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Low levels of LDL-C are risk factors for cardiovascular diseases.
Low levels of LDL-C are risk factors for cardiovascular diseases.
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____ are transported in plasma bound to apolipoproteins forming very low density lipoproteins (VLDL) and chylomicrons.
____ are transported in plasma bound to apolipoproteins forming very low density lipoproteins (VLDL) and chylomicrons.
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What is the primary purpose of measuring triglycerides?
What is the primary purpose of measuring triglycerides?
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Which combination poses an especially high risk for coronary heart disease?
Which combination poses an especially high risk for coronary heart disease?
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The triglycerides test principle involves the determination of triglycerides after enzymatic splitting with lipoprotein lipase using the indicator ______________.
The triglycerides test principle involves the determination of triglycerides after enzymatic splitting with lipoprotein lipase using the indicator ______________.
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High triglyceride levels primarily occur in diseases of the liver, kidneys, and pancreas.
High triglyceride levels primarily occur in diseases of the liver, kidneys, and pancreas.
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What is the Friedewald equation used for?
What is the Friedewald equation used for?
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Which equation is used to calculate LDL-C?
Which equation is used to calculate LDL-C?
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Hyperalbuminemia is mainly associated with dehydration.
Hyperalbuminemia is mainly associated with dehydration.
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Albumin is stable in serum for about __ days at 2-8°C.
Albumin is stable in serum for about __ days at 2-8°C.
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Study Notes
Lipids
- Lipids are constituents of living cells composed mostly of C-H bonds.
- They are molecules that combine water-insoluble dietary lipids and water-soluble proteins (apolipoproteins) for transportation throughout the body.
Classification of Lipids
- Fatty Acids:
- Short (4-6), Medium (8-12), Long (12-18), and Very long (16-24) chains
- Unesterified - bound to albumin
- Esterified - constituent of triglycerides or phospholipids
- Saturated - no double bonds
- Monounsaturated - one double bond
- Polyunsaturated - contain 2 or more double bonds
- Triglycerides:
- Contain 3 fatty acids attached to 1 molecule of glycerol by ester bonds
- No charged groups, water-insoluble, neutral lipid
- Phospholipids:
- Contain 2 fatty acids attached to 1 molecule of glycerol
- Amphipathic - hydrophobic head and hydrophilic tails
- Phospholipid head groups (hydrophilic): choline, inositol, inositol phosphates, glycerol, serine, and ethanolamine
Lipoproteins
- Classification of Lipoproteins:
- Chylomicrons:
- Largest lipoproteins with the lowest density
- Formed in the intestines, transport triglycerides after a meal
- Composed of 86% triglyceride, 5% cholesterol, 7% phospholipid, and 2% apolipoprotein
- VLDL (Very Low-Density Lipoprotein):
- Carries endogenous triglycerides synthesized in the liver
- Composed of 55% triglycerides, 19% cholesterol, 18% phospholipid, and 8% apolipoprotein
- IDL (Intermediate Density Lipoprotein):
- Transitional form between VLDL and LDL
- Carries endogenous triglycerides and cholesterol esters
- Composed of 23% triglycerides, 38% cholesterol, 19% phospholipid, and 19% apolipoprotein
- LDL (Low-Density Lipoprotein):
- Primary carrier of cholesterol
- Also known as "bad cholesterol"
- Composed of 50% cholesterol, 22% protein, and has apoprotein B-100 on its surface
- HDL (High-Density Lipoprotein):
- Also known as "good cholesterol"
- Removes excess cholesterol in peripheral tissues and transports it to the liver
- Composed of 50% protein, 28% phospholipids, 19% cholesterol, and has apoproteins A-I and A-II on its surface
- Lp(a):
- Composed primarily of cholesterol esters, phospholipids, and apolipoprotein (a) and B-100
- Elevated levels associated with increased risk for coronary heart disease, myocardial infarction, and cerebrovascular disease
- Chylomicrons:
Lipoprotein Physiology and Metabolism
- Lipid absorption: lipids are absorbed in the intestine and packed into chylomicrons
- Endogenous pathway: TAG in the liver is packed into VLDL through lipolysis
- Exogenous pathway: lipoprotein lipase hydrolyzes TAG in chylomicrons
- Reverse cholesterol pathway: HDL removes excess cholesterol and delivers it to the liver### Lipid Profile
- Lipid profile includes total cholesterol, HDL-C, LDL-C, VLDL-C, and triglycerides.
- Reference method: 3-step procedure of ultracentrifugation, heparin manganese precipitation, and Avell-Kendall assay.
- LDL-C estimation: indirect method uses Friedewald equation, direct method uses precipitation or homogeneous method.
Triglyceride Measurement
- Enzymatic method involves glycerol kinase.
- Correction methods for endogenous free glycerol: blanking, lipase-free reagent, and designated calibration blanking.
Lipoprotein Electrophoresis
- Uses agarose gel or PAGE.
- Not desirable for quantitation but useful for qualitative analysis.
Ultracentrifugation
- Preparative ultracentrifugation: uses sequential density adjustments to fractionate major and minor classes of lipoproteins.
- Density-gradient methods: permits fractionation of several or all classes of lipoproteins in a single run.
Hyperlipoproteinemia
- Classification: type I, type IIa, type III, type IV, and type V.
- Characteristics: elevated chylomicrons, LDL, IDL, VLDL, and triglycerides.
Lipid Abnormalities
- Familial combined hyperlipidemia (FCHL): increased plasma levels of total and LDL cholesterol or triglyceride.
- Familial hypertriglyceridemia: moderate elevation of triglyceride with excess VLDL production.
- Familial hypercholesterolemia: increased LDL cholesterol with normal or moderately elevated triglyceride.
- Hyperapobetalipoproteinemia: associated with VLDL and apo B-100 overproduction in the liver.
Apo A-1, Apo B, and Lp(a) Clinical Significance
- Apo A-1: major protein found in HDL, activates lecithin cholesterol acyltransferase, and removes free cholesterol from extrahepatic tissues.
- Apo B-100: major protein found in LDL, associated with increased risk of coronary artery disease.
- Lp(a): independent risk factor associated with impaired plasminogen activation and decreased fibrinolysis.
Liver Chemistries
- Liver functions: synthetic function, detoxification and excretion, storage, and transformation.
- Liver disease: hepatomegaly, jaundice, and liver chemistry tests (serum bilirubin, ALT, AST, ALP, and GCT).
Bilirubin Test
- Elevation in the test suggests cholestasis or liver injury.
- Conjugated bilirubin: water-soluble, produced by liver cells, and released in the common bile duct.
- Unconjugated bilirubin: produced by excessive destruction of erythrocytes.
Methods of Bilirubin Determination
- Jendrassik & Grof method: reacts with diazo reagent to produce purple azobilirubin.
- Evelyn & Malloy method: based on Van Den Bergh reaction, susceptible to hemoglobin interference.### Liver Chemistries
- Liver performs various functions and releases metabolites into the bloodstream, which can indicate liver disorders
- Liver tests can diagnose or monitor liver disease or damage
- Classification of liver chemistries:
- Bilirubin tests (serum bilirubin and urobilinogen tests)
- Liver protein tests (albumin, globulin, and prothrombin time)
- Liver enzyme tests (ALT, AST, GGT, and ALP)
Liver Enzyme Tests
- ALT (Alanine Aminotransferase):
- Found mainly in the liver, but also in other tissues
- Increases in serum when hepatic cells are damaged or destroyed
- Normal range: 7-45 U/L
- AST (Aspartate Aminotransferase):
- Found in the liver and other tissues
- Increases in serum when hepatic cells are damaged or destroyed
- Normal range: 5-35 U/L
- AST to ALT ratio: useful in distinguishing acute from chronic liver diseases
- Elevated levels of AST and ALT can indicate:
- Hepatocellular damage
- Acute viral hepatitis
- Drug/toxin-related hepatic necrosis
- Autoimmune hepatitis
Alkaline Phosphatase (ALP)
- Found in the bile canaliculi and bones
- Increases in serum during:
- Biliary obstruction or cholestasis
- Bone growth and development
- Inherited hyperphosphatasia
- Decreases in serum during:
- Inherited hypophosphatasia
- Normal range: varies with age and sex
Gamma-Glutamyl Transferase (GGT)
- Found in the cell membranes of the liver and gallbladder
- Increases in serum during:
- Cholestasis
- Chronic alcoholism
- Warfarin and phenytoin use
- Normal range: 6-55 U/L (men), 5-38 U/L (women)
Lipid Determinations
- Lipids are transported in plasma via lipoproteins
- Lipoproteins:
- Chylomicrons
- High-density lipoprotein (HDL)
- Low-density lipoprotein (LDL)
- Very low-density lipoprotein (VLDL)
- Intermediate-density lipoprotein (IDL)
- Lipid profile:
- Total cholesterol
- HDL cholesterol
- LDL cholesterol
- Triglycerides
- Importance of lipid profile:
- Risk assessment for cardiovascular disease
- Monitoring lipid-lowering therapy
Cholesterol Determination
- Total cholesterol level:
- Important factor in cardiovascular disease process
- High levels increase risk of atherosclerosis
- HDL cholesterol:
- Responsible for cholesterol uptake from cells
- High levels associated with reduced cardiovascular risk
- LDL cholesterol:
- Involved in cholesterol transport to peripheral cells
- High levels associated with increased cardiovascular risk
Triglycerides
- Triglycerides are esters of glycerol with three fatty acids
- Transported in plasma bound to apolipoproteins forming VLDL and chylomicrons
- Measurement used in:
- Screening for lipid status
- Monitoring lipid-lowering measures
- High triglyceride levels associated with:
- Atherosclerotic risks
- Liver, kidney, and pancreatic diseases
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Description
This quiz covers the structure and properties of cholesterol, a type of lipid molecule. It includes its composition, synthesis, and amphipathic characteristics.
