Day 4 - Proteins, Lipids Flashcards
A 10-12 hour fast is required in a panel for these lipids (4):
Total cholesterol
HDL
LDL
Triglycerides
- general rule: if serum looks clear after overnight refrigeration = normal triglycerides; if hazy/turbid = high triglycerides (above 3000 mg/dL), sample is lipemic
- no need to fast if testing cholesterol only
What do LDL contain the highest concentration of compared to the other lipoproteins?
Cholesterol
Hyperviscosity syndrome is associated with an increase in which immunoglobulin type?
IgM
-Waldenstrom’s Macroglobulinemia
What protein is used to assess the health of the BBB in a CSF sample? What would an increase or decrease indicate?
Albumin
Albumin not normally present in CSF; not permeable to BBB. INCREASED albumin in CSF indicates damaged BBB.
A normal immunoglobulin increase in response to infections would be a monoclonal or polyclonal increase?
Polyclonal
What do HDL contain the highest concentration of compared to the other lipoproteins?
Protein
Low HDL or high HDL increases risk of coronary heart disease?
Low HDL
What is primary amyloidosis? Name a complication it can cause…
Abnormal proteins clump together, forming deposits in cellular matrix of organs
Lungs (respiratory failure)
During protein catabolism, the amino group is removed by ___. The ___ ion produced during protein breakdown is converted to ___
Deamination
-carbon skeleton enters metabolic pathways
Ammonium
Urea
The most abundant protein in the body is… The next highest is…
Albumin
Globulin
Proteins linked to lipids are called… Proteins linked to carbohydrates are called…
Lipoproteins
Glycoproteins
-both are conjugated proteins
A protein that can react as both an acid and a base is called…
Amphoteric
What is the isoelectric point (pI)?
pH of a solution at which the net charge of a protein becomes zero
-neutrally charged
What happens if a solution’s pH > pI of a given protein? Below?
Above = protein is negatively charged
-protein lose H+ into solution
Below = protein is positively charged
- solution has high H+
- protein absorbs H+ ions
Anode is ___ charged. Cathode is ___ charged
Positively
-anion (-) moves towards anode (+)
Negatively
-cation (+) moves towards cathode (-)
Amino acid metabolism disorders are collectively called…
Aminoacidopathies
-PKU one of the common ones
The gold standard total protein assay is called…
Kjeldahl method
- protein precipitation followed by acid digestion
- nitrogen converted to ammonium bisulfite, which is measured
Why are urine and CSF poor samples to use for the biuret reaction for total protein?
Protein concentration too low (0.01 g/dL)
-need > 1 g/dL
Describe the biuret reaction for total protein
Cupric ions (Cu2+) complex with peptide bonds, producing a color change -more protein = more peptide bonds = darker color
What is the A/G ratio?
Albumin / Globulin
- total protein = albumin + globulin
- total protein - albumin = globulin
Prealbumin is also called… What 2 proteins does it transport?
Transthyretin
-made in liver
Thyroid hormone (thyroxine) Retinol
-transthyretin = TRANSports THYroxin and RETINol
The majority of urine protein is… Why is it excreted?
Albumin
MW of 60,000 means it’s low enough to pass through glomerulus but too large for reabsorption
2 main functions of albumin
Binding substances in blood
- carries hormones, drugs
- acts as blood buffer
Control osmotic pressure of blood
- maintains appropriate amount of fluids in tissues
- low albumin = edema, fluid buildup in body sites
The condition of protein in urine is called… Too much low MW proteins appearing in the urine is due to a defect in reabsorption called…
Proteinuria
Tubular Proteinuria
The plasma protein B2 microglobulin (B2M) increases in the urine during…
Kidney disease
- B2M should be reabsorbed
- tested for renal tubular function
CRP is an example of a globulin protein. When does it increase? What does it do?
Increases during infections
-one of the first acute phase proteins to rise in infections
Binds to bacteria (opsonization), promoting complement binding
-leads to phagocytosis
In multiple myeloma, the patient produces an excess of this specific part of the antibody’s structure…
Light chain
-abnormal production of monoclonal immunoglobulins
The light chain of antibodies are one of two types… Light chains appearing in the urine are called…
Lambda or kappa
Bence Jones proteins
-light chains have lower MW than full Ig structure
Bence Jones proteins can be detected with this test…
Electrophoresis
-also specific immunoassays for light chains
The majority of immunoglobulins are…
IgG (70%)
How can we tell the difference between elevated Ig due to infection vs elevated Ig due to multiple myeloma?
Infections = polyclonal
MM = monoclonal -paraproteins = abnormal protein
Monoclonal immunoglobulin SPE looks like this…
Gamma, beta or alpha2 increase
-ie multiple myeloma (gamma increase)
Nephrotic syndrome SPE looks like this…
Albumin lost, or very low
Alpha2 and beta increase
-retention of proteins like alpha2 macroglobulin
-albumin increase in urine
Acute-phase reactant proteins SPE looks like this… These proteins show up during…
Albumin decrease
Alpha and beta increase
-CPR = beta band
Inflammation
Liver disease SPE looks like this…
Albumin decrease
Gamma globulin increase
Multiple sclerosis patients show this band in CSF protein electrophoresis… Why?
Oligoclonal bands
Due to myelin basic protein, demyelination
- breakdown of myelin sheath in neurons
- only thing in CSF protein electrophoresis to watch out for
What are mott cells? What disease do they occur in?
Plasma cells with vacuoles
Multiple myeloma
In multiple myeloma, patients have an increase in myeloma protein called ___, which corresponds to this globulin band on the SPE…
M protein
Gamma
-“M spike” = monoclonal spike
What is the signature lab findings to diagnose multiple myeloma (2)?
M spike in serum or urine
CRAB
- Calcium > 11 mg/dL
- Renal creatinine > 2 mg/dL
- Anemia hgb < 10 g/dL
- Bone lytic lesions, osteoporosis
What is MGUS?
Monoclonal gammopathy of uncertain significance
- low levels of monoclonal paraprotein detected with increasing age
- minor spike in SPE without multiple myeloma
- mostly normal health, some evolve into MM
Waldenstrom macroglobulinemia is associated with overproduction of… Serum viscosity is…
IgM
-> 3 g/dL
Very high
-can be 4x thicker than normal serum
Difference between multiple myeloma and Waldenstrom’s Macroglobulinemia seen on a SPE is..
MM = high IgG heavy chain
Waldenstrom’s Macroglobulinemia = high IgM heavy chain
Saturated vs unsaturated - which has the double bond? Which is a solid and which is a liquid at room temperature?
Unsaturated
Saturated = solid (ie butter) Unsaturated = liquid (ie oil)
Saturated vs unsaturated - animal or plant origin?
Saturated = animal
Unsaturated = plant
What is the composition of a triglyceride?
3 fatty acids bound to glycerol
-hydrophobic
What is the composition of a phospholipid?
Phosphate head and 2 fatty acids bound to glycerol
- hydrophilic head, hydrophobic tail
- form cell membranes (phospholipid bilayer)
Is cholesterol hydrophobic or hydrophilic?
Both
- hydrophilic head
- hydrophobic tail
What are the 4 classes of lipoproteins based on ultracentrifugation electrophoresis patterns?
Chylomicrons
VLDL
LDL
HDL
What are apolipoproteins?
Protein free of lipids
- available to bind lipids
- ie apo A1 (HDL), apo B (VLDL, LDL)
- Lp(a) is a variant of LDL
Which lipoprotein is the lightest? Densest?
Chylomicrons
HDL
Which lipoprotein has the highest percentage of protein? What is this protein?
HDL
Apo A1
Which lipoprotein has the highest percentage of triglyceride?
Chylomicrons
VLDL have a composition highest in…
Triglycerides
-second highest after chylomicrons
Which lipoprotein has the highest percentage of cholesterol?
LDL
Of the 4 classes of lipoproteins, which are apo A and which are apo B?
apo A = HDL
-apo A1 = HDL
apo B = chylomicron, VLDL, LDL
- apo B-48 = chylomicrons
- apo B-100 = VLDL, LDL
-apo A and apo B are surface proteins
LDL and HDL - which is the “good” cholesterol?
HDL - higher in protein, free to absorb free cholesterol
- HDL removes excess cholesterol from cells via reverse cholesterol pathway
- LDL contains highest amount of cholesterol (60%)
Of the 4 classes of lipoproteins, where are each made?
Intestines = chylomicrons
Liver = VLDL/LDL, HDL
Once spun down, chylomicrons form this layer… Where is it located on the tube?
Cloudy layer, floating on top of serum
How are LDLs made?
VLDL converts to LDL via the enzyme LPL (lipoprotein lipase)
Difference between exogenous and endogenous pathways for lipoprotein metabolism
Exogenous = from diet, intestines
Endogenous = from liver
What is dyslipidemia? What are the 2 categories of dyslipidemia?
Disease associated with abnormal lipid levels
Hyperlipoproteinemia - high cholesterol, triglycerol, or both
Hypolipoproteinemia
For hypolipoproteinemia, is hypoalphalipoproteinemia or hypobetalipoproteinemia more dangerous?
Hypoalphalipoproteinemia (HDL)
- increased risk for CHD
- low HDL, so cannot get cholesterol out of cells
What are the 2 main methods to test for total cholesterol?
Colorimetric - using strong acids
Enzymatic - cholesterol esterase, cholesterol oxidase, peroxidase
- oxidase = measure oxygen consumed or hydrogen peroxide produced
- peroxidase = look for color change
What is the Friedewald equation to calculate LDL indirectly? What are the units?
LDL = Total Cholesterol - HDL - (Triglycerides/5)
-trig/5 is an estimate for VLDL cholesterol
mg/dL
To be able to use the equation to calculate LDL, these two things must be true
12 Hour fast
Triglycerides < 400 mg/dL
After lipoprotein electrophoresis, where are the following lipoproteins found on the gel: chylomicrons, VLDL, LDL, HDL
Chylomicrons - point of origin (remain in well)
-too big to move
VLDL - with pre-beta globulins
LDL - with beta globulins
HDL - with alpha globulins
-order seen on gel: chylo, beta, pre-beta, alpha
Besides poor diet/nutrition, low albumin levels are also caused by damage to either of these two organs…
Liver
-cannot make albumin
Kidneys
-rapid loss of albumin in urine
