Day 4 - Proteins, Lipids Flashcards by Kevin Tran

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

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What do LDL contain the highest concentration of compared to the other lipoproteins?

Cholesterol

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Hyperviscosity syndrome is associated with an increase in which immunoglobulin type?

IgM

-Waldenstrom’s Macroglobulinemia

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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.

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A normal immunoglobulin increase in response to infections would be a monoclonal or polyclonal increase?

Polyclonal

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What do HDL contain the highest concentration of compared to the other lipoproteins?

Protein

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Low HDL or high HDL increases risk of coronary heart disease?

Low HDL

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What is primary amyloidosis? Name a complication it can cause…

Abnormal proteins clump together, forming deposits in cellular matrix of organs

Lungs (respiratory failure)

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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

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The most abundant protein in the body is… The next highest is…

Albumin

Globulin

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Proteins linked to lipids are called… Proteins linked to carbohydrates are called…

Lipoproteins

Glycoproteins

-both are conjugated proteins

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A protein that can react as both an acid and a base is called…

Amphoteric

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What is the isoelectric point (pI)?

pH of a solution at which the net charge of a protein becomes zero
-neutrally charged

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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

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Anode is ___ charged. Cathode is ___ charged

Positively
-anion (-) moves towards anode (+)

Negatively
-cation (+) moves towards cathode (-)

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Amino acid metabolism disorders are collectively called…

Aminoacidopathies

-PKU one of the common ones

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The gold standard total protein assay is called…

Kjeldahl method

protein precipitation followed by acid digestion
nitrogen converted to ammonium bisulfite, which is measured

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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

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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

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What is the A/G ratio?

Albumin / Globulin

total protein = albumin + globulin
total protein - albumin = globulin

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Prealbumin is also called… What 2 proteins does it transport?

Transthyretin
-made in liver

Thyroid hormone (thyroxine)
Retinol

-transthyretin = TRANSports THYroxin and RETINol

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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

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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

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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

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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