(M) Lec 4: Lipids and Lipoproteins (Part 1) Flashcards
- referred to as “fats”
- is composed of C and H (hydrocarbons)
- is soluble to ORGANIC acids but insoluble in water
- functions as metabolic fuel, membrane stabilizers, and has many uses in different metabolic pathways (precursor for steroid hormones)
Lipids
Familiarize with the 5 major lipids
- Phospholipids (most abundant)
- Cholesterol
- Triglycerides
- Fatty Acids
- Fat-Soluble Vitamins (A, D, E, K)
Lipids provide how many times more energy than carbohydrates and proteins?
Twice as much
Match the ff. functions to the right fat-sloluble vitamin:
- For the eyes to avoid blindness
- For coagulation factors
- Prevents bone disorders and rickettsia
- An antioxidant
A, D, E, or K (provide all 4)
Sorry I’m trying to compress the cards as much as possible so just answer it altogether
- A
- K
- D
- E
Classification of Lipids
What are the 2 glycerol esters?
- Triglycerides
- Phosphoglycerides
Classification of Lipids
What are the 2 sterol derivatives?
- Cholesterol
- Phytosterol
Note: Sterols have RINGS (thank you beyonce)
What is the 1 sphingosine derivative/sphingolipid?
Ceramide
Note: The derivatives have 2 fatty acids attached to sphingosine
Classification of Lipids
This accounts for the 4 fat-soluble vitamins (A, D, E, K)
Terpenes
- a long chain of C-H bonds that terminate with a carboxyl group (RCOOH)
- the building blocks of lipids
- is mostly bound with albumin
- product of TAG hydrolysis and adipose tissue
- e.g. palmitic, stearic, oleic, linoleic, and arachidonic acid
Fatty Acids
Classification of Fatty Acids
As to length, choose among the ff.:
1. Short chain
2. Medium chain
3. Very long chain
4. Long chain
A. > 12 C atoms
B. 4-6 C atoms
C. 8-12 C atoms
D. > 20 C atoms
- B
- C
- D
- A
The no. of atoms of a fatty acid should be (odd/even)?
Even
Classification of Fatty Acids
As to no. of C=C bonds, choose among the ff.:
1. has one double bond
2. w/o double bonds
3. has 2 or more double bonds
4. w/ double bonds
A. Saturated
B. Unsaturated
C. Monounsaturated
D. Polyunsaturated
- C
- A
- D
- B
Classification of Fatty Acids
As to no. of C=C bonds and their structures, choose among the ff.:
1. is bent, liquid at RT, and not stable
2. is liquid at RT because the Cs are on the same side producing a kink
3. is solid at RT as it behaves like a saturated fatty acid
4. is linear, compact, solid at RT and harder to break
A. Saturated
B. Unsaturated
C. Cis configuration
D. Trans configuration
- B
- C
- D
- A
Fatty Acids (additional)
- This is the major dietary fatty acid
- These are not synthesized from carbohydrate precursors unlike most fatty acids but are instead supplied by the diet as they are essential fatty acids (2)
- These are precursors for the synthesis of eicosanoids (prostaglandins, thromboxanes, prostacyclins, and leukotrienes)
A. Elaidic Acid
B. Linolenic Acid
C. Polyunsaturated Fatty Acids
D. Linoleic Acid
- A
- B & D
- C
These 2 eicosanoids are for inflammation and clotting factor development, respectively
- Inflammation - Prostaglandins
- Clotting Factors - Thromboxanes
- are aka phosphoglycerides
- most abundant lipid derived from phosphatidic acid
- has 2 fatty acids + phosphorylated glycerol (structure is similar to TAGs but instead of 3, they have 2 fatty acids)
- is amphipathic (has hydrophillic and hydrophobic parts)
- forms include lecithin/phosphatidyl choline, sphingomyelin, and cephalin
Phospholipids
Phospholipids
Match them according to prevalence in the cell structure:
1. Lecithin
2. Cephalin
3. Sphingomyelin
A. 20%
B. 10%
C. 70%
- C
- B
- A
Phospholipids
- This is essential for the membrane and for diagnosing neonatal distress syndrome
- Acts as a reference material for the 3rd trimester of pregnancy which correlates to lung maturity of the baby
- Acts as a surfactant for effective gas exchange
Sphingomyelin
- this contains 3 molecules of fatty acid + 1 molecule of glycerol by ester bonds
- is very HYDROPHOBIC and water insoluble (it has no charge)
- forms adipose tissue
- when metabolized, it releases the fatty acids as its energy source (used when in a fasting state)
- additional info: lipoprotein lipase (LPL), epinephrine, and cortisol
Triglycerides (TAGs)
- this enzyme breaks the TAG and releases fatty acid and glycerol (lipemia clearing factor)
- removes entities that cause turbidity (TAG-rich lipoproteins) to plasma and serum
- a deficiency of this enzyme reduces clearance therefore there will be accumulation of TAGs
Lipoprotein Lipase (LPL)
- this evaluates suspected atherosclerosis and measures the body’s ability to metabolize fat
- requires a 12-14 hour fasting period to clear the chylomicrons
- serum or plasma can be used
- postural changes can decrease this analyte by 50% when laying down
Triglycerides (TAGs)
Triglycerides
If the sample is lipemic or will be delayed in processing, how do you preserve it?
Freeze at -20ºC
Make sure to warm and mix it before testing
Note: Frozen samples produce a different reading so it’s better to analyze immediately
Triglycerides
Bilirubin is considered an interference because as we age (around 45-65 years old), it (increases/decreases) by 2ml/dL every year
Increases
- nucleus is made out of cyclopentanoperhydrophenanthrene
- an unsaturated steroid alcohol with 4 rings and a single C-H side chain
- is synthesized in the liver and found on the surface of lipoproteins
Cholesterol
- its A ring and OH group are amphipathic
- not catabolized by most cells (not an energy source) but synthesized by animals
- a source of primary and secondary bile acids, steroid hormones, and vitamin D
- e.g. progestins, glucocorticoids, mineralocorticoids, androgens, and estrogens
Note: Bile acids are emulsifying agents
Cholesterol
Forms of Cholesterol
- makes up 70% of the cholesterol
- can be found in plasma or serum (at the CORE)
- is bound to fatty acid (hydrophobic form)
- undergoes esterification by the Lecithin Cholesterol Acyl Transferase enzyme (LCAT); is activated by APO A1
Cholesterol Ester
Forms of Cholesterol
- makes up 30% of the cholesterol
- this can be found in plasma, serum, and RBCs (at the SURFACE)
- the OH group attached to a ring is amphipathic
Free Cholesterol
This function of the LCAT enzyme transfers fatty acid from lecithin to a cholesterol ring
For esterification
Sources of Cholesterol
- This makes up 15% of the cholesterol in our body
- This makes up 85% of the cholesterol in our body and is the precursor for steroid hormones
Which is EXOGENOUS and which is ENDOGENOUS?
- Exogenous
- Endogenous
- one 18-carbon or longer fatty acid is bound to an amino group of sphingosine
- is important for cell membrane structure and the CNS
- has the ff. forms: sphingomyelin, galactosylceramide, and glucosylceramide
Ceramide
- has 5 branched chain units
- are intermediates in the metabolic production of cholesterol
- a precursor for the fat-soluble vitamins
Terpenes
What are the 3 major lipid components in plasma?
- Triglycerides (TAGs)
- Cholesterol
- Phospholipids
- these are a complex of lipids with specialized proteins
- transports TAG and cholesterol to sites of energy storage and utilization
Lipoproteins
- known as the protein portion of lipoproteins
- is an “amphipathic helix”
Apolipoproteins
- this helps keep lipids in the solution during bloodstream circulation
- it directs lipids to the correct target organs and tissues in the body
- it maintains structural integrity of the complex
- these serve as ligands for cell receptors
- are activators/inhibitors of various enzymes that modify lipoprotein particles
Apolipoproteins
Alauporic Nomenclature (apolipoproteins)
- Helps activate the LCAT enzyme
- An arginine-rich apolipoprotein
- The thin-line lipoprotein which activates the LCAT reaction
- Is produced by the liver and intestine
- Causes high LDL levels; higher risk for developing CAD and Alzheimer’s
A. Apo A1
B. Apo E
C. Apo D
D. Apo E4
Yes, there are 4 choices for 5 questions, one answer will be doubled
- A
- B
- C
- A
- D
Alauporic Nomenclature (apolipoproteins)
What are Apo B-100 and Apo B-48 made out of? (2 separate answers)
- Apo B-100: VLDL and LDL
- Apo B-48: Chylomicrons
Alauporic Nomenclature (apolipoproteins)
What Apo C protein activates the LPL enzyme?
Apo C2
Lipoproteins
- the largest and least dense
- density is < 0.95 kg/L
- composed of 90% TAG and 1-2% CHON
- contains apolipoproteins B48, C, E, and A4
Chylomicrons
Note: Apo B48 is EXCLUSIVE for chylomicrons
Lipoproteins
- is produced by the intestine (exogenous)
- completely cleared within 6-9 hours post-prandial
- transports exogenous/dietary TAGs to the liver, muscles, and fat deposits
Chylomicrons
Lipoproteins
This appears milky in apperance at the top of the specimen sample when you let the sample stand for several hours OR the patient did not fast
Chylomicrons
Lipoproteins
- has a density of 0.95-1.006 kg/L
- composed of 65% TAGs (fasting plasma), 16% CE, and 6-10% CHON
- contains apolipoproteins B100, C, and E (C and E are minor apolipoproteins)
- it has a uniform and homogenous turbidity after overnight standing
- is secreted by the liver (endogenous)
- it transports endogenous TAGs from the liver to muscles, fat deposits, and peripheral tissues
Very Low Density Lipoprotein (VLDL)
Lipoproteins
- the smallest but densest lipoprotein
- aka “alpha lipoprotein”
- has a density of 1.063-1.21 kg/L
- composed of 30% PL, 25% CE, and 45-50% CHON
- contains apolipoproteins A1 (main), A2, and C
- produced by the liver and intestine (endogenous)
- transports excess cholesterol (reverse cholesterol transport)
High Density Lipoproteins
Lipoproteins
This kind of HDL transports cholesterol back to the liver (is more cardioprotective than the other HDL) more efficiently
HDL 2 (more effective than HDL 1)
Lipoproteins
This process of HDL maintains equilibrium; refers to collecting excess cholesterol in the peripheral tissue to go back to the liver (reused or excreted as bile)
Reverse Transport
Note: HDL is anti-atherogenic (good cholesterol)
Lipoproteins
High Density Lipoprotein Reference Values:
What are the low (cut-off level) and high values?
Low: < 40mg/dL
High: ≥ 60mg/dL
Lipoproteins
- a major end product resulting from VLDL catabolism
- the most cholesterol rich and most atherogenic
- density is 1.019-1.063 kg/L
- composed of 50% CE and 18% of CHON and PL
- contains apolipoproteins B100 (MAIN) and E
- produced by the liver
- this transports cholesterol to the peripheral tissues
Low Density Lipoproteins (LDL)
Lipoproteins
Low Density Lipoprotein Reference Values:
1. < 100mg/dL
2. 100-129 mg/dL
3. 130-159 mg/dL
4. 160-189 mg/dL
5. ≥ 190 mg/dL
A. Optimal
B. Very High
C. High
D. Borderline
E. Near/Above Optimal
- A
- E
- D
- C
- B
Minor Lipoproteins
- the product of VLDL catabolism
- is converted to LDL
- density is 1.006-1.019 kg/L
- migrates either in the pre-B or B region
- major lipids include endogenous TAG and CE
- major apolipoprotein is B100
Intermediate Density Lipoprotein (IDL)
Minor Lipoproteins
If IDL is not cleared, it could result to what condition?
Type 3 Lipoproteinemia
Minor Lipoproteins
- known as the “sinking pre-B lipoprotein”
- produced in the liver
- these are LDL-like particles with Apo-A linked to Apo-B 100 by a disulfide bond
- density is 1.045-1.080 kg/L
- major lipids include CE and phospholipids
- the secondary transporter of cholesterol to tissues
Lipoprotein (a)
Minor Lipoproteins
Lipoprotein (a) is a/an (dependent/independent) risk factor for atherosclerosis
Independent
Minor Lipoproteins
An increased Lipoprotein (a) level indicates what conditions?
Premature CHD and Stroke
Use ELISA and turbidimetric methods to detect it
Minor Lipoproteins
What is the normal reference range for lipoprotein (a)?
< 20mg/dL to 1500mg/dL
Minor Lipoproteins
Lipoprotein (a) is similar to LDL in what 2 parameters?
- Density
- Electrophoretic mobility
Minor Lipoproteins
- a specific and sensitive indicator of cholestasis
- indicative of obstructive jaundice and LCAT deficiency
- contains phospholipids and free cholesterol
- has Apo-C and albumin
Lipoprotein (x)
Minor Lipoproteins
This is considered as a dysfunctional HDL
Oxidized HDL
Minor Lipoproteins
- the “floating B lipoprotein” and “VLDL rich in cholesterol”
- has the same density with VLDL (< 1.006 kg/L) but migrates with LDL in the B region
- there’s an increase in Type 3 hyperlipoproteinemia or dysbetalipoproteinemia
B-VLDL
Minor Lipoproteins
Failure to convert VLDL to LDL leads to the accumulation of what?
IDL
Lipid Metabolism
This process:
- needs pancreatic lipase to clear fatty acids (converting them into dietary lipids)
- involves small lipids forming aggregates with bile acids to be absorbed
- it forms micelles which are absorbed by the intestines
Lipid Adsorption
Lipid Metabolism
This process/pathway:
- causes LPL to catalyze a hydrolysis reaction which releases glycerol and fatty acids from chylomicrons
Exogenous Pathway
Lipid Metabolism
Exogenous Pathway:
Which receptors found in specific organs can Apo-C and Apo-E bind to? (2 answers)
- Apo-C: Receptors on adipose tissue
- Apo-E: Receptors on hepatocytes
Lipid Metabolism
This process/pathway:
- hydrolyzes VLDL which turns into IDL
- the IDL is returned to the liver and further hydrolyzed by hepatic lipase
- it releases glycerol and fatty acids which leave behind IDL remnants called LDLs
Endogenous Pathway
- this is produced in the liver and is a component of HDL
- it transfers TAGs from Apo-B lipoproteins in exchange for cholesterol esters in HDL
- it catalyzes the transfer of CEs to Apo-B100-containing particles in exchange for TAGs
- it connects the forward and reverse cholesterol transport pathways
Cholesterol Ester Transfer Protein (CETP)
This pathway is considered to be an alternative pathway for HDL metabolism
+ a deficiency of this analyte leads to the production of large cholesterol-laden (heavily loaded) HDL
Cholesterol Ester Transfer Protein (CETP)
Enzymes in Lipoprotein Metabolism
This enzyme is for the efflux of cholesterol from peripheral cells into HDL
ATP-binding casette protein A1 (ABCA1)
Enzymes in Lipoprotein Metabolism
This enzyme:
- hydrolyzes TAG in lipoproteins (CM and VLDL)
- has phospholipids and Apo-C2 as cofactors
Lipoprotein Lipase
Enzymes in Lipoprotein Metabolism
This enzyme:
- hydrolyzes TAG and phospholipids from HDL
- hydrolyzes lipids in VLDL and IDL
Hepatic TAG Lipase
Enzymes in Lipoprotein Metabolism
This enzyme:
- esterifies cholesterol from HDL
- has Apo-A1 as a co-factor
- the end product is lysolecithin and cholesterol ester
Lecithin Cholesterol Acyltransferase (LCAT)
Enzymes in Lipoprotein Metabolism
This enzyme hydrolyzes phospholipids and TAGs in HDL
Endothelial Lipase
Sample Considerations
Kindly choose the correct words to make the sentences true:
- Total cholesterol, TAGs, and HDL-C when frozen is (satisfactorily/unsatifactorily) analyzed
- Lipemic samples occur in (fasting/non-fasting) blood
- Lipemic samples may be (pre/post-treated) by ultracentrifugation and enzymatic cleavage
- Lipoproteins are differentiated based on (electrophoresis/flow cytometry) and ultracentrifugation
- (Plasma/Serum) is the best choice in measuring lipoproteins
- Satifactorily
- Non-fasting
- Pre-treated
- Electrophoresis
- Serum
Note: Ultracentrifugation helps for tests that use turbidity to measure concentration
Sample Considerations
Non-HDL C is computed using what formula?
Total Cholesterol - HDL
Note: LDL is computed manually
Sample Considerations
Samples can be stored at (given temperature) for how many days?
1. 4ºC
2. -20ºC
3. -70ºC
A. 1-3 months
B. 3 days
C. For longer
- B
- A
- C
Sample Considerations
Although serum is the best choice in measuring lipoproteins, some labs like to use EDTA/heparinized plasma however there is a major disadvantage in relation to the machine, what is that disadvantage?
It can clog the machine
Sample Considerations
When performing a lipid profile test, what parameters are included? (5)
- Cholesterol
- TAG
- HDL
- LDL
- VLDL
Patient Preparation
Fasting specimens are used for what 2 analyes?
TAG and LDL
Patient Preparation
Kindly choose the correct words to make the sentences true:
- Due to CETP, concentrations of LDL-C and HDL-C (rise/decline) temporarily after eating
- When a standing patient reclines, extravascular water transfer to the vascular system and (dilutes/concentrates) non-diffusable plasma constituents
- There is a/an (increase/decrease) of as much as 10% in the concentrations of TC, LDL-C, and HDL-C [based on question #2]
- Decline (this is due to chylomicrons)
- Dilutes
- Decrease
Total Cholesterol
What specimen is used: plasma, serum, both, or non of these?
Both
Total Cholesterol
How long is the fasting period for a serum sample of total cholesterol?
10-14 hours
Total Cholesterol
TOF: Total cholesterol cannot be taken from a non-fasting sample
False (it is allowed, but some doctors prefer a fasting sample)
Total Cholesterol (TESTING)
- Principle of the test: The dehydration and oxidation of cholesterol to form a colored compound
- There are double bonds and an OH-group in the sterol structure
Chemical (Colorimetric)
Total Cholesterol (TESTING)
For Chemical (Colorimetric)
1. This method is considered the BEST method and has an end product of Cholestadienyl Monosulfonic Acid (GREEN)
2. This method has an end product of Cholestadienyl Disulfonic Acid (RED)
3. This method produces a GREEN-colored reaction
4. This method produces a RED-colored reaction and is sensitive
A. Liebermann-Burchardt Reaction
B. Para-Toluene Sulfonic Acid Reaction
C. Salkowski Reaction
D. Tsugaeff Reaction
- A
- C
- B
- D
Total Cholesterol (TESTING)
For Chemical (Colorimetric)
Glacial acetic acid, Acetic anhydride, and Conc. H2SO4 are the components to what mixture?
Color Developer Mixture
Total Cholesterol (TESTING)
For Chemical (Colorimetric)
1. Colorimetry (Pearson, Stern, and Mac Gavack)
2. C + E + S + Precipitation (Schoenheimer, Sperry, Parekh, and Jung)
3. C + E + Saponification (Abell-Kendal)
4. C + Extraction (Bloors)
A. One Step Method
B. Two Step Method
C. Three Step Method
D. Four Step Method
- A
- D
- C
- B
Total Cholesterol (TESTING)
This method:
- is precise but not specific
- produces a pink-red reaction
- not used as a reference method due to interfering substances
Enzymatic Method (by Flegg)
Total Cholesterol (TESTING)
What is the CDC’s reference method for Flegg’s Enzymatic Method?
ABELL, LEVY, and BRODIE Method
Total Cholesterol (TESTING)
ABELL, LEVY, and BRODIE Reference Method:
1. Saponification
2. Extraction
3. Colorimetry
A. Leibermann-Burchardt Reaction
B. Alcoholic KOH
C. Hexane
- B
- C
- A
Total Cholesterol (TESTING)
Interferences:
What levels of ascorbic acid and bilirubin are considered interferences in the enzymatic method? (2 answers)
Ascorbic Acid: >30 mg/dL (falsely increased)
Bilirubin: >5mg/dL
Note: Use Potassium Ferricyanide to counteract Bilirubin
Total Cholesterol (TESTING)
Reference Values:
1. < 200 mg/dL
2. >240 mg/dL
3. 200-239 mg/dL
A. Normal
B. Borderline High
C. High Cholesterol
- A
- C
- B
Total Cholesterol (TESTING)
What is the conversion factor?
0.026 mmol/L
Total Cholesterol (TESTING)
This is the highest order method for serum cholesterol analysis (gold standard)
Isotope Dilution Mass Spectrometry (IDMS)
Total Cholesterol (TESTING)
Increased or Decreased?
- Hyperlipoproteinemia TII, III, V
- Biliary cirrhosis
- Nephrotic syndrome
- Poorly controlled diabetes mellitus
- Alcoholism
- Primary hypothyroidism
Increased
Total Cholesterol (TESTING)
Increased or Decreased?
- Severe hepatocellular disease
- Malnutrition
- Severe burns
- Hyperthyroidism
- Malabsorption syndrome
Decreased
