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302 Cards in this Set
- Front
- Back
Lipids are soluble in ______ but insoluble in _______
|
organic solvents, water
|
|
Lipids yield ______ or ______ on hydrolysis
|
fatty acids or complex alcohols
|
|
Four major functions of lipids
|
biological membranes
efficient way to store excess calories provide readily available energy reserves serve as essential vitamins and hormones |
|
Fatty acids have what type of structure?
|
R-COOH
|
|
In nature, most fatty acids are ____ and have an ______ number of carbon atoms
|
unsaturated, even
|
|
Structure of triglycerides
|
glycerol backbone with three fatty acids attached
|
|
Most of the lipids that are obtained in the diet are _______
|
triglycerides
|
|
What type of bond is formed between the carboxylic acid of the fatty acid and the hydroxyl group of the glycerol backbone in triglycerides?
|
ester bond
|
|
Phospholipid structure
|
2 esterified fatty acids (bound to glycerol) + phosphate + polar head group
|
|
Cholesterol is a good source of energy (T/F)
|
False, it is not easily broken down.
|
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Bile acids are more ______ than cholesterol
|
polar
|
|
Bile acids act as _______ in the intestine to break down ______.
|
emulsifiers/detergents, dietary fat
|
|
Lipoproteins are less water soluble than lipids (T/F)
|
False, lipoproteins are more soluble due to the charge of the amino acids in the protein portion
|
|
Which human plasma lipoprotein has the highest amount of protein?
|
HDL
|
|
HDL is also known as ______ lipoprotein
|
alpha
|
|
LDL is also known as _______ lipoprotein
|
beta
|
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In a lipoprotein, more lipid means greater _______ and lower _______
|
size, density
|
|
In order to be transported in blood, lipids must combine with ________
|
water-soluble compounds such as apolipoproteins
|
|
Triglyceride must always be on the inside of lipoproteins because __________
|
of their very hydrophobic nature
|
|
Low-density lipoproteins are derived from _________
|
VLDL by lipolysis
|
|
What is lipoprotein (a)?
|
LDL-like particles that are heterogeneous in size and density. They resemble plasminogen in structure and interfere with fibrinolysis. High plasma levels indicate higher risk for cardiovascular disease.
|
|
High-density lipoprotein is capable of removing _________
|
excess cholesterol from peripheral cells
|
|
Apoproteins C and E are released when ______
|
lipoprotein lipase forms LDL from VLDL
|
|
Apoproteins associated with chylomicrons
|
B48, C1-C3, E
|
|
Apoprotein associated with LDL
|
B100
|
|
VLDL apoproteins
|
B100, C1-C3, E
|
|
HDL apoproteins
|
A1, A2, C1-C3, E
|
|
IDL apoprotein
|
B-100
|
|
Functions of apoproteins (for lipids)
|
Activate enzymes involved in lipid metabolism, maintain structural integrity of lipid/protein complex, delivery of lipids to cells via recognition of cell surface receptors
|
|
Four major pathways in lipoprotein metabolism
|
Lipid absorption, Exogenous pathway, Endogenous pathway, Reserve cholesterol transport pathway
|
|
Cholesteryl ester is hydrolzed by cholesterol esterase (pancreatic secretion) to form _________ and _______.
|
free cholesterol, free fatty acid
|
|
Triglycerides must be ______ before passing through the intestinal membrane
|
hydrolyzed by lipase to free glycerol and fatty acids
|
|
Lipase cannot directly attack triglyceride because of difference in ______
|
charge, lipase is hydrophilic while triglyceride is hydrophobic
(bile acids solve this problem by forming micelles) |
|
Once the fatty acids and glycerol are inside the intestinal cell, _____ are reformed and combines with apoproteins to form _______
|
triglycerides, chylomicrons
|
|
Chylomicrons are transferred from intestinal cells to the _______
|
lymphatic vessels
|
|
All lipoprotein generated by the liver is in the form of _______
|
VLDL
|
|
Function of lecithin cholesterol acyltransferase. What is an important cofactor for this enzyme?
|
Esterifies a fatty acid to a cholesterol molecule to allow import into cells. Apoprotein A-1.
|
|
Atherosclerosis
|
the deposition of lipids in various tissues within the body
|
|
Risk factors for atherosclerosis
|
>45 years men, >55 years women, family history, cigarette smoking, hypertension, diabetes mellitus, low HDL level, high LDL level, high total cholesterol, severe obesity, physical inactivity, stress
|
|
Laboratory guidelines for desirable lipid levels
|
Total cholesterol < 200 mg/dL
LDL < 100 mg/dL HDL > 60 mg/dL |
|
Triglyceride level is not directly associated with risk of cardiovascular disease, but the recommended level is _______
|
< 150 mg/dL
|
|
Lipoprotein (a) desired level
|
<30 mg/dL
(independent risk factor) |
|
How does lipoprotein (a) contribute to cardiovascular disease?
|
Lp(a) has a structure very similar to plasminogen, and competes with plasminogen for activators, blocking their action. Plasmin is therefore unable to form and lyse clots.
|
|
High HDL levels are associated with what populations?
|
pre-menopausal women, people who exercise regularly, people with a low but healthy weight.
|
|
Insulin, estrogen and thyroxine have what relationship with total cholesterol levels?
|
Inverse
|
|
How do statin drugs work?
|
They inhibit HMG-CoA reductase (an enzyme which converts acetyl coA to cholesterol). This increases HDL and reduces LDL.
|
|
How do fibrate drugs work?
|
Activate LPL, promote rapid VLDL turnover, decrease VLDL secretion
However, these drugs are somewhat toxic to the liver |
|
Cholestyramine decreases plasma cholesterol by ________
|
binding bile acids to prevent reabsorption by the liver
Not very well tolerated |
|
Hyperlipoproteinemia
|
elevation of low density and high density lipoproteins
Primary: inborn error of metabolism Seconday: diabetes, hormone replacement, nephrotic syndrome, hepatic disorder, blood pressure medication |
|
Hypertriglyceridemia primarily results from __________
|
lipoprotein lipase deficiency
|
|
The portal triad consists of
|
a vein, an artery and a bile duct
|
|
Reticuloendothelial cells break down hemoglobin into ________
|
bilirubin
|
|
Indirect or unconjugated bilirubin is bound to ________
|
albumin
|
|
Bilirubin diglucuronide is known as _________
|
conjugated or direct bilirubin
|
|
Urobilinogen may be excreted in ______
|
urine or feces
|
|
Jaundice
|
excess bilirubin in body, can produce yellow pigment in skin or eyes
|
|
Kernicterus
|
Excess unconjugated bilirubin in brain tissue
|
|
Delta bilirubin is ________
|
a type of conjugated bilirubin that is bound to albumin covalently
|
|
Unconjugated bilirubin is never excreted by the ______. This is because __________.
|
kidney, the albumin molecule is too large to pass through the glomerulus
|
|
Prehepatic jaundice is caused by _________.
|
increased hemoglobin breakdown (i.e. hemolytic anemia, shortened hemoglobin lifespan, pernicious anemia)
|
|
Prehepatic jaundice laboratory results
|
Serum
indirect bilirubin increased direct bilirubin normal Urine direct bilirubin negative urobilinogen increased Stool urobilinogen increased |
|
Hepatic jaundice laboratory results (due to cell damage)
|
Serum
increased indirect bilirubin increased direct bilirubin Urine positive direct bilirubin increased urobilinogen Stool variable urobilinogen |
|
Posthepatic jaundice laboratory results
|
Serum
increased indirect bilirubin increased direct bilirubin Urine direct bilirubin positive decreased to negative urobilinogen Stool decreased to negative urobilinogen |
|
Causes of hepatic jaundice
|
Conjugation failure, transport failure, cell damage
|
|
Cause of post-hepatic jaundice
|
obstruction of the bile duct
|
|
Specimen requirements for bilirubin assay
|
protected from light, serum/heparinized plasma, not hemolyzed
|
|
The most common elevated element in hypercholesterolemia is _______ secondary to other disease
|
LDL cholesterol
|
|
Familial hypercholesterolemia is due to a defect or deficiency in ________
|
LDL receptos
|
|
Familial hypercholesterolemia results in an increased risk for ________
|
atherosclerosis
|
|
The treatment of choice for familial hypercholesterolemia is ______ because they decrease _______ LDL and increase _______
|
statin drugs, endogenous, LDL receptors
|
|
Triglceridemia may occur secondary to ______
|
diabetes mellitus or hormonal abnormalities
|
|
Severe hypertriglyceridemia may occur due to deficiency of ____ or _____
|
LPL, apoprotein CII
|
|
When LPL is absent, increased levels of chylomicrons cause lipemia even in fasting states (T/F)
|
True, serum triglyceride levels may exceed 500 mg/dL
|
|
Combined hyperlipoproteinemia consists of what?
|
presence of increased serum cholesterol and triglyceride
|
|
Familial combined hyperproteinemia is due to an overproduction of _____ and _____
|
VLDL and B100
|
|
Familial dysbetalipoproteinemia is due to _________ and results in increased _______ and _______
|
presence of a rare form of apoE, VLDL, chlyomicron remnants
|
|
Hypoalphalipoproteinemia is caused by
|
decrease in HDL exhibited from absence or non-detectable levels of apo A-1.
|
|
The sample of choice for analysis of lipids is ______
|
serum
plasma with lithium heparin may also be used |
|
What is the minimum fast for a triglyceride sample?
|
12 hour fast
|
|
Is fasting necessary for cholesterol analysis?
|
No, however fasting is necessary if a lipid panel is being performed
|
|
Chylomicrons will be distributed throughout a serum sample (T/F)
|
False, chylomicrons will generally float to the top. This is helpful in determining if a sample is fasting or not. Additionally, it is important to mix the sample well before analysis for this reason.
|
|
HDL cholesterol analysis requires isolation of HDL by _______ of LDL/VLDL followed by ________. The supernatant HDL may then be measured with the same method as _______.
|
precipitation, centrifugation, total cholesterol
|
|
An alternative method of isolating cholesterol from HDL involves treatment of the serum with ______, which lyses HDL but _____ LDL and VLDL without lysis.
|
a detergent, coats
|
|
Friedewald formula
|
total cholesterol = HDL + LDL + VLDL
|
|
VLDL =
|
triglyceride/5
as long as the sample is fasting (triglyceride < 400 mg/dL) |
|
Measurement methods for LDL
|
direct immunoassay, ultracentrifugation
|
|
In congestive heart failure, liver function is compromised by _______
|
hypoxia
|
|
Conjugated or direct bilirubin is ______ is water
|
soluble
|
|
Unconjugated or indirect bilirubin is _______ in water
|
insoluble
|
|
What enzyme is responsible for bilirubin conjugation?
|
Uridyldiphosphate glucuronyl transferase
|
|
Prehepatic jaundice results in increased ________ bilirubin
|
unconjugated
|
|
Total bilirubin reference range
|
0.2 to 1.2 mg/dL
|
|
Causes of prehepatic jaundice
|
hemolytic anemia, ineffective erythropoiesis, neonatal physiological jaundice
|
|
In prehepatic jaundice, bilirubin levels rarely exceed 5 mg/dL (T/F)
|
True, this is because the liver is still functioning normally
|
|
Unconjugated bilirubin (can/can not) cross the blood-brain barrier
|
Can, this may result in kernicterus causing severe neurologic damage
|
|
Treatment for neonatal physiological jaundice
|
phototherapy with monochromatic blue like to oxidize bilirubin to more soluble end products to enhance renal excretion
|
|
Intrahepatic jaundice
|
problem is within the liver (impaired uptake, absent/decreased enzyme activity, defective excretion due to absence of transport molecule)
Liver enzymes ALT and AST will be highly elevated compared to LD |
|
Visible icterus occurs above ______ bilirubin
|
3 mg/dL
|
|
Posthepatic jaundice
|
caused by physical barrier to bile excretion (obstructive, artesia), highly increased conjugated bilirubin, will be excreted in urine
Biliary enzymes will be elevated (GGT and ALP) |
|
Alcoholic jaundice is characterized by
|
osmolalic increase, very high GGT (as compared to ALP)
|
|
LD stands for
|
Lactate dehydrogenase
|
|
If true hepatic disease exists, what enzymes will be increased?
|
AST, ALT, LD, usually with ALT>AST
|
|
Decreased albumin is a very good marker for _______
|
liver disease
|
|
Amino acids are linked to each other through _____ bonds with the ______ group of one amino acid combining with the _______ group of another
|
peptide, carboxyl, amino
|
|
Aminoacidopathies
|
inherited enzyme defects that inhibit metabolism of certain amino acids
cause several medical complications due to build-up of toxic amino acids and byproducts in blood |
|
For amino acid analysis in adults, sample should be collected in a tube containing ______ and should be drawn after a ________.
|
lithium heparin, 6-8 hour fast
|
|
______ may be used as a sample for screening amino acid analysis.
|
Random urine
|
|
Primary structure of a protein is determined by _________
|
number and types of amino acids and their sequence in the polypeptide chain
|
|
Tertiary structure is determined by ________
|
the way the twisted chains or pleated sheets of amino acids fold back on themselves to form a 3D structure
|
|
Zwitterion or ampholyte
|
amino acid that at physiologic pH has both carboxyl and amino sites ionized
|
|
Reference range for protein
|
6.5-8.3 g/dL
|
|
Factors influencing the rate of an enzymatic reaction
|
pH, temperature, concentration of enzyme
|
|
Increased temperature ________ the rate of an enzymatic reaction unless the temperature is too high (greater than 40 degrees celsius) which ________ the protein
|
increases, denatures
|
|
Hydrogen ion concentration changes the ionizable groups on enzymes and ______ the rate of the enzymatic reaction due to a change in ________
|
decreases, shape of the protein
|
|
Most enzymes work best between the pH of ____________. One exception is _______.
|
7 to 8, gastric enzymes
|
|
Ionic strength is the ____________
|
cumulative concentration of all solutes
|
|
Body enzymes are optimized for ______ conditions (osmolality)
|
isotonic (300 mmol/L)
|
|
A change in ionic strength changes the _______ of the medium in an enzymatic reaction, resulting in a _________ of the enzyme, resulting in a _________ rate of reaction.
|
polarity, change in shape, decreased
|
|
Enzymes are measured in terms of _______
|
activity
international unit per liter = micromoles of substrate used up per minute of incubation per liter |
|
Enzyme concentration (zero order) =
|
change in absorbance per minute/(extinction coefficient*length of light path) x 10^6 micromoles/mole x dilution factor
|
|
Advantages of kinetic enzyme assay
|
can inspect the data and use only the zero order reaction, can detect and eliminate lag phase or substrate exhaustion
|
|
Advantage of one-point enzyme assay
|
Faster, batching
|
|
Name the three isoenzymes of CK and where each is found.
|
CK-1 (BB) - brain and intestine
CK-2 (MB) - mostly cardiac muscle CK-3 (MM) - skeletal and cardiac muscle CK may also be found in the kidney, uterus, thyroid, liver and prostate. |
|
Total CK levels are always increased in ______ and ______. These enzymes are increased ______ the upper limit of normal.
|
acute myocardial infarction, muscular dystrophy, 50-100x
|
|
Reference range of CK
|
25-170 U/L, slightly higher in men than women
|
|
A hemolyzed sample will cause a falsely ______ value for CK due to the presence of ________
|
increased, AK (similar enzyme)
|
|
Isoenzymes of LD and where each is found
|
LD1 - heart, RBC, kidney
LD2 - heart, RBC, kidney LD3 - lungs LD4 - liver/skeletal muscle LD5 - liver LD6 - CAD with liver disease |
|
Describe the change in LD in acute myocardial infarction
|
LD1 > LD2
In health individuals, LD2 > LD1 |
|
Reference range for LD
|
100 - 225 U/L
|
|
Aspartate aminotransferase is found in:
|
liver, cardiac and skeletal muscle
|
|
Aspartate aminotransferase increases in
|
myocardial infarction (peaks @ 24 hours), pulmonary embolism, acute hepatocellular disorders (very high levels), skeletal muscle disorders
|
|
Alanine aminotransferase is predominantly in the ______
|
liver
|
|
Alanine aminotransferase is ______ than AST in acute inflammatory conditions of the liver
|
greater
|
|
Oxidation of NADH + H+ results in a _______ in absorbance
|
decrease
|
|
Alkaline phosphatase is most significant in ______ and _____ disorders
|
hepatobiliary, bone
|
|
The Regan isoenzyme of ALP is a ________
|
tumor marker
|
|
Reference range for ALP
|
30-90 U/L (can be as high as 125 depending on what method is used)
|
|
Acid phosphatase is specific for the _______
|
prostate gland
|
|
Major significance of ACP is ________. However, it is not _______.
|
prostatic carcinoma (particularly metastasized carcinoma), specific (mostly used to monitor therapy)
|
|
Gamma-glutamyl transferase has clinical applications in ______ and _______ disorders.
|
liver, biliary.
|
|
_______ induces synthesis of GGT.
|
alcohol abuse
|
|
Amylase catalyzes the breakdown of ______ and ______
|
starch, glycogen
|
|
Amylase is utilized in the diagnosis of _________.
|
acute pancreatitis
|
|
Reference range of amylase
|
35-125 U/L
|
|
Lipase hydrolyzes __________
|
ester linkages of fats to produce alcohols and fatty acids.
|
|
An increase in lipase is specific for ________.
|
pancreatitis
|
|
Cholinesterase hydrolyzes _______.
|
esters of choline to destroy poisons or drugs.
|
|
Cholinesterase is found in ______, _____ and _______.
|
liver, heart, white matter of brain
|
|
Cholinesterase is a sensitive marker for ___________.
|
organophosphate poisoning
|
|
A decrease in cholinesterase is seen in ________, ______, ______ and _______.
|
liver disease, starvation, burns and insecticide poisoning,
|
|
ischemia
|
lack of oxygenation due to interrupted blood flow to an organ
|
|
angina pectoris
|
chest pain from lack of oxygen to the heart muscle
characteristic crushing pain, often radiation to left arm, neck or shoulder blade accompanied by sweating and "feeling of doom" |
|
arrythmia
|
abnormal rhythm of heart beat due to abnormal stimulation or interruption of the nerve impulse
|
|
myocardial infarction
|
heart attack, necrosis of cardiac muscles due to interruption in blood flow and oxygen to the heart
|
|
atherosclerosis
|
hardening, roughing and narrowing of the blood vessels due to fatty plaque accumulation
|
|
congestive heart failure
|
inadequacy of pumping by the heart, decreased circulation of blood
|
|
7 classic symptoms of heart disease
|
dyspnea, chest pain, syncope, edema, cyanosis, fatigue, palpitations
|
|
S-T elevation on an ECG is diagnostic for ________, however it is only seen in ______ of patients.
|
myocardial infarction, 50%
|
|
In myocardial infarction _____ > ______ (LD isoenzymes).
|
LD1 > LD2
|
|
CKMB is elevated _______ after myocardial infarction and peaks at _______.
|
6-8, 18-24
|
|
CKMB index =
|
(CKMB activity/total CK activity) * 100
Reference range 1.5-6% |
|
CKMB levels return to normal _____ after MI.
|
2-3 days
|
|
Troponin I is the most sensitive and specific marker for _______
|
myocardial infarction
|
|
Troponin rises above normal level ______ after myocardial infarction
|
6-8 hours
|
|
Troponin peaks at ______ after myocardial infarction
|
2-4 days
|
|
Myoglobin increases ______ after myocardial infarction
|
2-4 hours
|
|
Myoglobin is an early marker for ______ but it is not ______.
|
myocardial infarction, specific
|
|
CRP is a marker for ______
|
inflammation
|
|
The level of CRP increases when in relationship to MI?
|
a few hours to a few days before a heart attack
|
|
Increased levels of homocysteine have recently been recognized as a _______
|
cardiac risk factor
|
|
An increase in homocysteine is correlated with _______
|
damage to the endothelial lining of blood vessels
|
|
In congestive heart failure, weakness in the left ventricle leads to ________.
|
edema of the tissues
|
|
Symptoms of CHF include
|
edema, increase blood pressure, shortness of breath, easy fatigue, dizziness, difficulty in walking short distances, compromised renal function
|
|
Patients who have had severed or repeated myocardial infarctions are at high risk for ________
|
congestive heart failure
|
|
B-type natriuretic peptide is a specific marker of ________
|
edema due to heart failure
|
|
BNP increases the _______ of the kidney to compensate for _________.
|
urine output, fluid accumulation associated with CHF.
|
|
Ischemia modified albumin
|
when in contact with ischemic tissue, albumin is altered, decreasing its ability to bind certain metals (esp. cobalt)
|
|
Separation techniques depend on differential ________.
|
physical characteristics
|
|
Common separation techniques in the clinical laboratory include _____ and ______.
|
electrophoresis, chromatography
|
|
Separation of charged particles during electrophoresis occurs because _________.
|
different molecules move at different rates
|
|
In electrophoresis, if the pH of the buffer is more basic than the pI, the protein carries a net _____ charge and will migrate to the ______.
|
negative, anode (positive pole)
|
|
Negatively charged molecules will move toward the _______ charged electrode known as the _____.
|
positively, anode
|
|
In addition to the electrical potential and the charge of the molecule, what forces can affect the movement of molecules in electrophoresis?
|
Friction due to shape (symmetry) and size
|
|
How is the voltage in the electrophoretic system chosen?
|
to minimize heat and buffer evaporation while maximizing resolution
|
|
The buffer in an electrophoretic system moves in the _____ direction to the flow of negatively charged sample molecules
|
opposite
|
|
Electroendoosmosis
|
Large highly charged proteins may migrate towards the like-charged electrode because they absorb OH ions from the buffer
|
|
Velocity of migration of molecules in electrophoresis is controlled by _________.
|
the net charge of the particle, size and shape of the particle, strength of the electric field, chemical and physical properties of the supporting medium and electrophoretic temperature.
|
|
Hepatic cirrhosis shows what patten on protein electrophoresis?
|
beta-gamma bridging and decreased albumin peak
|
|
Alpha-1-antitrypsin deficiency may cause what conditions?
|
emphysema, hepatic cirrhosis
|
|
A hemolyzed sample will cause what electrophoretic pattern?
|
Free hemoglobin peak between alpha-2 and beta or
Hemoglobin-haptoglobin complex peak in the alpha-2 region |
|
(T/F) Significant protein is normally found in the urine
|
False, protein in urine is usually in negligible amounts
|
|
Elevated urine protein is an early indicator of ______.
|
renal impairment
|
|
What are Bence Jones proteins? They are present in what disorder?
|
Ig light chains, multiple myeloma
|
|
What is the proper sample for measurement of urine protein?
|
24 hour urine collection
|
|
What pattern will be seen in CSF electrophoresis in multiple sclerosis?
|
oligoclonal banding of gamma proteins
|
|
Major lipids
|
fatty acids, triglyceride, cholesterol, cholesteryl esters, phospholipids, bile acids
|
|
Cholesterol is slightly polar due to the ______
|
free OH group at C3
|
|
Cholesteryl ester is esterified at the _______
|
C3-OH group
|
|
Chylomicrons are _____ triglyceride and ______ cholesterol.
|
84%, 7%
|
|
VLDL is _____ triglyceride and ______ cholesterol
|
44-60%, 16-22%
|
|
IDL is ______ triglyceride and _____ cholesterol
|
23%, 29%
|
|
LDL is _______ triglyceride and ______ cholesterol
|
11%, 62%
|
|
HDL is _______ triglyceride and _______ cholesterol
|
3%, 19%
|
|
IDL and VLDL migrate near the ____ region in electrophoresis
|
Pre-beta
|
|
LDL is readily taken up via LDL receptors in ______ and ______ cells.
|
liver, peripheral
|
|
CETP
|
plasma protein collects triglycerides from VLDL or LDL and exchanges them for cholesteryl esters from HDL, and vice versa.
|
|
Insulin, estrogen and thyroxine have what type of relationship with total cholesterol level?
|
inverse
|
|
Hypoalphalipoproteinemia is associated with increased risk of ____ due to _____.
|
CHD, build-up and blockage of blood vessels from excess LDL
|
|
Hyperbetalipoproteinemia results in lack of _______ because of poor ______. This leads to _______.
|
LDL uptake in steroid generating tissue, receptor specificity, deposition of cholesterol esters in tissues
|
|
Triglyceride analysis reactions
|
Detergent reagent breaks up lipoprotein particles into
their parts, releasing triglycerides into the solution triglycerides + H2O + lipase yields fatty acids + glycerol glycerol + ATP(Mg+2) + glycerol kinase yields glycerol-1-phosphate +ADP glycerol-1-phosphate + O2 + glycerol phosphate oxidase yields DHAP + H2O2 H2O2 + 4-AAP + dye-precursor + peroxidase yields H2O + quinonimine dye (colored) |
|
Potential problems with triglyceride analysis
|
free glycerol in the sample, standards are water soluble but triglyceride is water-insoluble (lipase and detergents must work), average molecular weight assumption, redox contaminants
|
|
Total cholesterol analysis reactions
|
detergent reagent breaks up lipoprotein particles into their parts, releasing cholesterol and cholesterol esters into the solution
cholesterol-ester + H2O + cholesterol esterase yields cholesterol + fatty acids cholesterol + O2 + cholesterol oxidase yields cholestenone + H2O2 2H2O2 + reduced dye + peroxidase yields 4H2O + oxidized dye (colored) |
|
Problems in total cholesterol analysis
|
interference from redox agents
|
|
Define enzymes
|
organic molecules that accelerate biochemical reactions
|
|
Enzymes act as ______ and emerge from reactions ______.
|
catalysts, unchanged
|
|
Why does the clinical laboratory usually measure enzymes?
|
To identify or monitor presence and amount of damaged tissue
|
|
AST conducts what reaction?
|
Transamination on aspartate
|
|
Most transaminases require what cofactor?
|
pyridoxal phosphate (a derivative of B6)
|
|
Most oxidases use what as a cofactor?
|
Oxygen
|
|
Creatine kinase performs what reaction?
|
Phosphorylation of creatine
|
|
Amylase conducts what reaction?
|
hydrolysis of starch (amylose)
|
|
Alkaline phosphatase conducts what reaction?
|
Removal of phosphate at alkaline pH
|
|
Enzymes ____ the rate of reaction but do not change the ______.
|
increase, equilibrium constant
|
|
Enzymes work by _____ the activation energy of the reaction. This happens because enzymes form _____ with the substrate.
|
decreasing, temporary intermediate bonds
|
|
Enzymes reduce the ______ needed to activate reactions
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free energy
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Define zero-order kinetics
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Substrate concentration is high enough to saturate all enzyme present, reaction velocity is at max, rate is dependent only on enzyme concentration
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Michaelis-Menten equation
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V = Vmax[S] / (Km = [S])
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Lineweaver-Burk equation
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1/V = Km/Vmax[S] + 1/Vmax
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Y intercept of Lineweaver-Burk plot
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1/Vmax
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X-intercept of Lineweaver-Burk plot
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-1/Km
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Enzyme activity is extremely sensitive to its ______.
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shape
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Measurement Reaction for CK (from creatine)
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Creatine + ATP + CK ↔ Creatine phosphate + ADP
From ADP: (optimal pH = 9.0) ADP + phophoenolpyruvate + PK ↔ pyruvate + ATP Pyruvate + NADH + H+ + LD ↔ Lactate + NAD+ |
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Measurement reaction for CK (from creatine phosphate)
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(faster, optimal pH = 6.8)
Creatine phosphate + ADP + CK ↔ Creatine + ATP ATP + Glucose + HK↔ Glucose- 6-phosphate + ADP Glucose- 6-phosphate + NADP+ + G6PD ↔ 6-Phosphogluconate + NADPH + H+ |
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Sources of error for CK analysis
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hemolysis, exercise
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Measurement reaction of LD
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Lactate + NAD+ + LD ↔ Pyruvate + NADH + H+
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Sources of error in measuring LD
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hemolysis, refrigeration
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AST reference range
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15-30 U/L
|
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Measurement reaction of AST
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2-oxoglutarate + L-aspartate + AST ↔ L-glutamate + oxaloacetate
Oxaloacetate + NADH + H+ + MD ↔ NAD+ + L-Malate |
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At what wavelength does NADH/NADPH have peak absorbance?
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340 nm
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AST must use ______ serum.
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non-hemolyzed
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ALT reference range
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6-37 U/L
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Increased levels of ALT are seen in what type of disorder?
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hepatocellular
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Measurement reactions for ALT
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alanine + alpha-ketoglutarate + ALT ↔ pyruvate + glutamate
pyruvate + NADH + H+ + LD ↔ lactate + NAD+ |
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4 major isoenzymes of ALP. These enzymes differ in _____ stability.
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bone, liver, placenta, intestine, heat
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Phenylalanine inhibits ____ and ____ isoenzymes of ALP more than ______ and ______.
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intestinal, placental, bone, liver
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Measurement reactions for ALP
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p-Nitropphenyl + ALP ↔ p-Nitrophenol + Phosphate ion
Increase in Abs. of p-nitrophenol is measured @ 405nm |
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Sources of error for ALP measurement
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high fat, left at room temp or refrigerated
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ACP is measured by what reaction?
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p-nitrophenol reaction (pH = 5)
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What are potential sources of error for ACP measurement?
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hemolysis, sample left at room temperature (loss of CO2 resulting in pH change)
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Reference range of GGT
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up to 45 U/L
|
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In addition to alcohol abuse, what other conditions result in increased GGT?
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diabetes, MI, pancreatitis
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Measurement reactions for GGT
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gamma-glutamyl-p-nitroanilide + glycylglycine + GGT yields p-nitroaniline (colored dye) + gamma-glutamylglycylglycine
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Tissue sources of amylase
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salivary glands and pancreas
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Sources of error in amylase measurement
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high triglyceride, EDTA or citrate anticoagulant
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Lipase is specific for diagnosis of _____.
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acute pancreatitis
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Reference range for lipase
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10-200 U/L
|
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Measurement reaction for lipase
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triglycerides + lipase yields fatty acids + glycerol
glycerol + ATP(Mg+2) + glycerol kinase yields glycerol-1-phosphate + ADP glycerol-1-phosphate + O2 + glycerol oxidase yields DHAP + H2O2 H2O2 + 4-AAP + dye-precursor yields H2O + quinonimine dye (colored) |
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Source of error in cholinesterase measurement
|
hemolysis (RBCs contain acetylcholinesterase)
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In the body, iron is utilized in what 3 types of molecules?
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enzymes, hemoglobin, myoglobin
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As iron decreases, hepcidin synthesis ______. This results in release of iron from the _____ and _______ absorption in the duodenum.
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decreases, spleen, increased
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What test is the gold standard for iron assessment?
|
bone marrow examination
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The serum iron assessment is sensitive to ________
|
mild iron deficiency
|
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Transferrin saturation
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The ratio of serum iron or iron-binding capacity
Serum iron/TIBC * 100 |
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Which assessment is the most accurate indicator of iron supply to bone marrow?
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Transferrin saturation
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The serum transferrin receptor assay determines the cells' ______. It becomes _______ in iron deficiency.
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need for iron, elevated
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The best diagnostic test for iron deficiency is _______ as it measures the _______ in the body.
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serum ferritin, iron stores
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R/F ratio
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sTfr/serum ferritin
used to provide estimate of iron stores |
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Iron levels can become transiently increased by iron ingestion so samples should be fasting. (T/F)
|
True. Additionally, iron has a diurnal variation so morning samples are best.
|
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Colorimetric iron measurement reactions
|
Fe3+:Transferrin + acid yields Fe3+ + apotransferrin
Fe3+ + Reducing Agents yields Fe2+ Fe2+ + Complexing chromogen yields Colored complex |
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TIBC measurement
|
Saturate all binding sites with excess Fe+3
Remove excess unbound iron Measure protein-bound iron (per iron method) Various methods are used to remove the excess iron |
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UIBC =
|
TIBC - Serum iron
|
|
Oral contraceptives can increase serum ____ levels
|
transferrin
|
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UIBC measurement
|
Adds a fixed amount (in excess) Fe+3 at a neutral pH to saturate iron binding sites
The uptake of iron by the unoccupied serum iron-binding sites is measured by a serum iron method as a decrease in free iron. |
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Ferritin may be measured by ______.
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immunoassay
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Transferrin may be directly measured by _______.
|
immunological methods
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Serum iron reference range
|
50-160 micrograms/dL
|
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TIBC reference range
|
250-410 micrograms/dL
|
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Laboratory results for iron deficiency anemia
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decreased serum iron, increased TIBC, decreased % saturation, decreased ferritin
|
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iron laboratory results for hemolytic anemia
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increased iron, decreased to normal TIBC, increased percent saturation, increased ferritin
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iron laboratory results for hemochromatosis
|
increased serum iron, normal to decreased TIB, increased percent saturation, increased ferritin
|
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iron laboratory results for lead poisoning
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decreased serum iron, normal TIBC, normal to increased % saturation, normal to increased ferritin
|
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What is the normal blood lead level for children?
|
<10 mcg/dL
|
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The free erythrocyte protoporphyrin assay is sensitive for low lead levels (T/F)
|
False, this test is not sensitive below 35 mcg/dL
|
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Is the zinc protoporphyrin test specific for lead poisoning?
|
No, this test is also sensitive for iron deficiency and anemia of chronic disease
|
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What enzymes of the heme synthesis pathway are blocked by lead poisoning?
|
ALA dehydratase, coproporphyrinogen oxidase, ferrochelatase
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What treatment is curative for congenital erythropoietic porphyria?
|
bone marrow transplant
|
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Define porphyrin
|
cyclic compound formed by methylene linkage of 4 pyrrole rings
|
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Uro and coproporphyrinogens are soluble in _______.
|
water
|
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protoporphyrin is soluble in ______.
|
lipids
|
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Both porphyrinuria and porphyrinemia are (primary or secondary) conditions.
|
secondary
|
|
Categories of porphyrias
|
hepatic, erythropoietic
cutaneous, acute |
|
Acute intermittent porphyria
|
hereditary defect of hepatic porphobilinogen deaminase, increased delta-ALA in urine, increased porphobilinogen in urine
|
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Congenital erythropoietic porphyria
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Gunther's disease, deficiency in uroporphyrinogen III cosynthase, increased ALA, uroporphyrinogen and coproporphyrinogen
|
|
Porphyria cutanea tarda
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Most common porphyria, deficiency of uroporphyrinogen carboxylase, hepatic, increased uroporphyrin in urine, normal ALA and PBG
|
|
Watson-Schwatz test
|
Tests for porphobilinogen
PBG + Ehrlich’s gives red color Must do extractions to prevent interference |
|
Porphyrin test
|
Add amyl alcohol, ethel ether and glacial acetic acid to urine
Shake, allow to separate Upper, organic layer will fluoresce if porphyrins are present |
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Reference range for free or zinc protoporphyrin
|
20 – 80 μg/dL
|
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Serum level of LD peaks at _____ hours and returns to normal ____ to ____ days following AMI.
|
12, 7-14
|
|
Troponin levels return to normal _____ days after MI.
|
5-10
|
|
What compounds have been shown to help reduce homocysteine levels in the blood?
|
B vitamins, folic acid
|
|
In congestive heart failure, _____ slows, allowing _______ to accumulate in tissues.
|
circulation, water/waste
|
|
In patients with congestive heart failure, BNP serum levels are usually greater than _______.
|
100 pg/mL
|