Unit 7: Proteins and other Nitrogen-Containing Compounds Flashcards

Test: Serum BUN/Creatinine

Sample: Plasma or Serum (preferably transported separated from the erythrocytes)

Method: Quantitative Spectrophotometry

Result: BUN 84 mg/dL Creatinine 1.8 mg/dL Reference Range
(Ratio 10-20)

Disease or Condition: Valvular Regurgitation (Prerenal Azotemia)

Test: Serum BUN/Creatinine

Sample: Plasma or Serum (preferably transported separated from the erythrocytes)

Method: Quantitative Spectrophotometry

Result: BUN 57 mg/dL Creatinine 5.8 mg/dL Reference Range
(Ratio 10-20)

Disease or Condition: Transitional Cell Carcinoma of the Bladder (Postrenal Azotemia)

Test: Serum Protein Electrophoresis

Sample: Serum

Method: Quantitative Capillary Electrophoresis

Result: Elevated a1 and a2 bands

Disease or Condition: Acute Phase Reaction

Test: Serum Albumin

Sample: Serum

Method: Quantitative Spectrophotometry

Result: 2.8 g/dL Reference Range (3.5-5.0 g/dL)

Disease or Condition: Cirrhosis after a Fasciola hepatica infection

Test: Synovial Fluid Uric Acid

Sample: Synovial Fluid from a joint aspirate

Method: Quantitative Spectrophotometry

Result: 7.2 mg/dL Reference Range (No Reference Range in Synovial fluid)

Disease or Condition: Gout

Test: Serum Uric Acid

Sample: Serum

Method: Quantitative Spectrophotometry

Result: 9.3 mg/dL Reference Range (2.5-6.1 mg/dL)

Disease or Condition: Tumor Lysis Syndrome

If you see the phrase “mousy odor” on the registry exam, they are
likely referring to PKU.

A phenylalanine-restricted diet, rich in grains, fruits, and vegetables, and low in meats, eggs, cheese, and milk.

Fumarylacetoacetate hydrolase

Dark brown or black urine

Leucine, Isoleucine, and Valine

Homocystinuria

None. Remember, it is caused by a deficient transporter protein which allows for cystine reabsorption by the kidney.

The correct answer is A) This fact is the most likely to be tested clinical nuance that will give the answer away every time. It’s just screaming at you that this patient has homocystinuria. The most common mutation is the CBS gene, screened with the Guthrie test using L-methionine sulfoximine to inhibit bacterial growth, but the increased level of methionine in the sample will still allow for the bugs to grow. If you have growth on a Guthrie test, that is positive! The treatment of vitamin B6
.

The correct answer is C) The hallmark of this disease is that there is an elevated level of branched chain amino acids, which are leucine, isoleucine, and valine. The deficient enzyme is BCKD. Treatment is a BCAA-restricted diet.

The correct answer is D) This man was likely never screened in Ghana, but was inadvertently adhering to a phenylalanine-restricted diet by eating only vegetarian food. This all changed once he and his family were introduced to the wonders of American table trash and had the means to procure it. PKU is the most common inherited aminoacidopathy in America, occuring about 1 in 15,000 births (He is an immigrant, so this statistic wouldn’t apply to him). The deficient enzyme is phenylalanine hydroxylase and the gene is PAH. Screening for PKU now occurs across the country equally. Screening is performed by a Guthrie test using

Ascites and edema. This is a case where the synthetic capacity of the
liver has been compromised, so we would expect to see a low plasma albumin level in this patient. Since she has a decreased protein level in her blood, the plasma colloidal osmotic pressure (oncotic pressure) is also decreased. The compartments of the body (e.g. the abdomen) attempt to keep adequate protein levels for cellular functioning. Therefore, the oncotic pressure surrounding the tissues and in the abdomen is relatively greater than the plasma oncotic pressure. This causes water to be sucked in between the tissues causing edema and swelling. Also remember the peritoneum? That is a cavity, which also retains proteins. If a patient has decreased serum oncotic pressure, the will get abdominal swelling and the peritoneal cavity will fill up
with fluid, which we call ascites. No bueno

Short answer is it depends. The longer answer is that it depends on where the alanine is added. If it is added to the end of the polypeptide chain, then it would change the primary structure, which would likely affect the secondary, tertiary, and quaternary structures. If the alanine is added to an amino acid side chain, then it will likely affect tertiary and quaternary structures

Principle: Protein digestion assay, measures released Nitrogen

Use: Reference method

Principle: Cu ²⁺ and peptide bonds create a purple color

Use: Routine method; performed in an alkaline medium

Principle: Dye binds to the protein which causes a shift in the absorbance of the dye

Use: Used for research

BUN and Serum Total Protein

None! It is considered a nonessential amino acid and can be synthesized from phenylalanine. Of note, It is an amino acid which is richly used in adrenal medullary hormones (e.g. epinephrine, norepinephrine, dopamine) and thyroid hormone. All of hormones that stimulate activity in the body.

α₁-antitrypsin

The correct answer is B) Remember, this method is the routine one that it is used in everyday laboratory testing. This uses Cu ²⁺ , which binds to peptide bonds and creates a purple color. The color change is measured at 540 nm.

The correct answer is A) This is the only structure that would likely NOT be denatured. B) is formed by weak bonds and would likely be the first to disintegrate. One could argue that C) would also likely NOT be denatured because they are covalently-bonded side chains. What I wanted to get you to understand is that the Primary structure is the hardest one to break down. D) would likely be different because if the secondary structure is changed, then the proteins would likely NOT fit as well as they are supposed to.

The correct answer is A) It would be increased because of the presence of Ceruloplasmin, the copper transport protein. This patient likely has Wilson’s disease, a genetic defect in the body’s ability to metabolize copper, causing it to be deposited everywhere. This results in cirrhosis and occasionally neurologic effects as we

DNA degradation, adenine and guanine

Negatively birefringent crystals. This means that if you’re looking with
a light filter, the needles that are pointing in one direction will refract blue light, and the needles that point 90˚ from that refract yellow light. Quick memory trick: If needles which are ParaLLel to the filter are yeLLow, it’s Gout! In image 4, The filter would be pointed in a horizontal plane the horizontal crystals are yellow, that means this is Gout. Notice that the vertical crystals are blue.

The patient will likely have hypouricemia

0.6 - 1.1 mg/dL

An EDTA or Heparin tube on ice. The plasma should be immediately separated from the red cells and assayed or stored

Ammonia (NH3)

the correct answer is D) This patient has gout and the podagra described (gouty tophi over the metatarsophalangeal joint), is typical of gouty arthritis. Even the weight of a bedsheet, can send these patients off the edge.

The correct answer is A) It binds to Ca²⁺ and chelates it, making it unavailable for assaying, but also unavailable for protein function. Ca ²⁺ is used as a cofactor for a bunch of enzymes that are involved in protein and uric acid degradation. Different labs require different samples. Some just say that they need plasma or serum from any tube.

The correct answer is B) The point of this question is to help you
recognize that numerous drugs will affect ammonia levels, and specifically smoking cigarettes even a few hours before the sample is taken, can drastically increase the ammonia value reported. Red cells contain two to three times the levels of ammonia inside of them, so when you have hemolysis and spill out the red cell all over the place,
then you will falsely increase the ammonia result. Remember, to be accurate, these samples MUST be collected on ice and ran immediately

Picric acid is explosive, even crust that forms on the cap can ignite
when the cap is turned

0.6 - 1.1 mg/dL

We have a few equations to be able to do this:
Creatinine Clearance equation CrCl = (U_Cr x V_Ur ) / (S_Cr x 1,440 min/24 hours)
U_Cr = Urine Creatinine
S_Cr = Serum Creatinine
V_Ur = volume of urine in 24 hours

The next one to know would be the equation for estimated GFR or the Cockroft-Gault Formula GFR = [(140-Age) x weight (kg)] / [72 x SCr]

10.7 mL/min. This man is in severe renal failure and is probably in line for his weekly dialysis appointment, or at least he should be.

The next one to know would be the equation for estimated GFR or the Cockroft-Gault Formula GFR = [(140-Age) x weight (kg)] / [72 x SCr]

Divide the urea concentration by 2.14. This is easy to remember which one is bigger because urea is the large molecule, and BUN stands for Blood Urea Nitrogen, so it’s obviously just looking for nitrogen. If you want to calculate the urea concentration, then you multiply BUN by 2.14.

BUN:Cr ratio = 46. This is indicative of a prerenal etiology. The most common being something to cause a decreased amount of blood to flow through the kidneys. This would include dehydration, shock, congestive heart failure, or anything else the leads to a decrease in circulating blood volume

The correct answer is C). This would be a definitive laboratory finding of prerenal azotemia. If the ratio is >20, then that’s just suggestive, but over 40 is definitive. The reason why this happens is because Creatinine is much more dependent on the glomerular filtration rate, rather than kidney function. As long as the kidneys are being perfused at 50% capacity, the creatinine value doesn’t increase. Prerenalazotemia can be caused by renal hypoperfusion; which can be caused by dehydration, renal vasoconstriction, or a myocardial infarction. This causes activation of the renin-angiotensin-aldosterone system, antidiuretic hormone, and sympathetic nerve signals to increase reabsorption of water, salt, BUN, and creatinine so that the kidney can be adequately perfused. BUN is reabsorbed at a MUCH greater rate than creatinine, thereby causing the drastic increase in BUN. A) Bun >80 mg/dL can occur in this clinical situation, but the big point is that the creatinine would be normal or slightly elevated, making answer A. the most correct. B) Cr >8.2 mg/dL would show up in chronic, renal failure. These patients are possibly dialysis dependent. D) Cystatin C is an analyte which is completely filtered by the glomeruli and is constantly produced by all nucleated cells. It is NOT secreted in the PCT, but it does have some clinical situations which confound analysis … just like creatinine

The correct answer is A) The reason for this is because with postrenal azotemia, your patients have a fairly normal BUN/Cr. This normal ratio will remain until the backup of urine flows retrograde up the ureters and into the kidneys, causing renal failure. The normal BUN and
Creatinine values tell the clinician that this patient has NOT impaired their renal function yet. The PSA value is quite elevated, and is the likely cause of the clinical signs of this patient not being able to pee (this is called urinary hesitancy). B) BUN 86 mg/dL Cr 3.7 mg/dL PSA 28 ng/mL has a BUN/Cr ratio of 23, which indicates a possible prerenal etiology. Something like this could also show up in early
renal failure or dialysis-controlled renal failure. The PSA value is quite high, indicating that this is probably caused by benign prostatic hypertrophy and may be the beginning of postrenal renal failure. C) BUN 213 mg/dL Cr 8.9 mg/dL PSA 5.4 ng/mL has a BUN/Cr ratio of 23 as well and a PSA value near the upper limit of normal. D) BUN 28
mg/dL Cr 0.7 mg/dL PSA 3.4 ng/mL hs a low BUN and Creatinine value with a ratio of 40. This is a perfect example to demonstrate how the BUN:Creatinine ratio can ONLY be used in cases of pathology. Because according to the ratio, he has prerenal renal failure,
but his values show absolutely NO kidney damage at all. Keep that in mind when interpreting BUN and creatinine in the future!

The correct answer is B) which shows that she is NOT in renal failure, because her values are close to normal. She has a nephrotic picture with urine positive for protein, PMNs, and renal epithelial cells. We would expect her BUN and Creatinine values to be fairly normal, because she presented to the physician right when these symptoms started. So she likely doesn’t have any renal failure yet, but we can look for other symptoms to give the answer away, then we know
what labs to look for. She’s got frothy urine (proteinuria), generalized edema, and a nephrotic urinalysis. Then you go back to realize that she had a streptococcal infection just 2 weeks ago, and that’s the clincher! This is a pretty textbook picture of poststreptococcal glomerulonephritis (PSGN).

A) BUN 10 mg/dL Creatinine 18.1 mg/dL is physiologically improbable. C. BUN 87 mg/dL Creatinine 4.3 mg/dL is a sign of renal failure, but is strange because the creatinine is elevated significantly higher than the BUN should be. This is likely caused by an increased production of creatinine, either via rhabdomyolysis (skeletal muscle destruction) or an increased intake of cooked meat D. BUN 117 mg/dL Creatinine 3.2 mg/dL is a sign of probable prerenal failure with the ratio at 36

1. Proteinuria greater than 3-3.5 g/24 hour

2. No increased serum albumin <25 g/l

3. Clinical evidence of peripheral edema

4. Severe hyperlipidaemia (total cholesterol >380 mg/dL) is often present

produced in the liver

produced by plasma cells

produced in the RBC

Albumin

note: Largest peak and migrates the fastest on electrophoresis

Gammas are cations so they go the other way

6.0 - 8.3 g/dL (may vary from lab to lab)

maintains oncotic pressure (colloidal osmotic pressure)

Increased catabolism - Physical injury

Decreased synthesis - Primary (liver disease), Secondary (malabsorption, malnutrition)

Increased loss - Renal protein loss

emphysema and cirrhosis

Note it is called antitrypsin because it destroys titrypsin and titrypsin destroyed proteins.

AAT makes up 90%, most common, of the

• Major glycoprotein released in inflammation
• Carrier of cationic drugs - Digoxin, trimethoprim, and vancomycin

• First globulin from the fetus to cross the placenta in utero
• High levels seen in Spina Bifida, Anencephaly, abdominal wall defects, and all neural tube defects

Serum protease inhibitor. Found between the A1 and A2 zones.

Acute Phase Reactant, binds hemoglobin, and is removed in the spleen. Haptoglobin prevents hemoglobin from being removed in the glomeruli. Increased in inflammation, intravascular hemolysis, and smoking positively associated with hemolytic anemia. M ore hemaglobin means for haptoglobin needs to be there to bind it.

Copper containing protein, oxidizes iron, Decreased in Wilson’s Disease, causing excessive Cu to accumulate in liver and brain causing cirrhosis. Binds to copper.

Protease inhibitor (inhibits complement, coagulation, and fibrinolytics). Largely increased in nephrotic syndrome. Decreased in pancreatitis, RA, and multiple myeloma. N ote similar to to α1Antitrypsin and α1Antichymotrypsin it breaks down proteins.

Transports Ferric (Fe3+) cations to storage sites (marrow, liver, spleen) Acute Phase Protein, transports iron, and increased in hemochromatosis

Plasma glycoprotein that removes heme from circulation. Increased in Diabetes, inflammation, and pregnancy. Decreased in hemolytic diseases

Carry lipids in the plasma, classified as LDL-C

Found on nucleated cell membranes, especially on lymphocytes Elevated in multiple myeloma, leukemias, hepatitis, Rheumatoid Arthritis, Systemic Lupus Erythematosus, and AIDS

They work with gamma globulins.

Acute phase reactant and an indicator of tissue injury or inflammation

Acute phase reactant and a coagulation factor. Increased in pregnancy and women on OCPs. Decreased in consumptive coagulopathies

Over 30 glycoproteins with many effects on the body, think of cell lysis

Acute phase proteins, Decreased in Disseminated Intravascular Coagulopathy (DIC), Paroxysmal Nocturnal Hemoglobinuria (PNH), infections with meningococci, or malnutrition

Gamma globulins are thought of as antibodies

Gamma globulins that have been mistakenly created against our own cells are called autoimmune diseases, meaning that we are attacking ourselves

A/G ratio = albumin / globulin (Total Protein - Albumin = Globulin)

Normal range is 1.1-1.5

<1.1

1.multiple myeloma (immunoglobulin hyperproduction)

2.cirrhosis (lack of albumin synthesis)

3.nephrotic syndrome (loss of protein in the urine)

High A/G ratios (>1.5)

1.leukemias (lack of immunoglobulin production)

2.genetic immunoglobulin deficiencies (Common Variable Immunodeficiency [CVID], selective Ig deficiencies)

Serves as a transport protein or shuttle

1. Synthesized by the Liver
2. Acute Phase Protein
3. Presence indicates adequacy of nutrition
4. Lack of prealbumin suggests liver failure

is cancer of the plasma cells, resulting in uncontrolled hyperproduction of immunoglobulin

Leads to pathologic fractures and hypercalcemia

Patients generally have bone pain and hypercalcemia along with proteinuria

Low α1 macroglobulin

high β2 micro globulin

can caused by hemodilution, decreased production, increased loss of protein inadequate nutrition, water intoxication, nephrotic syndrome, or liver failure

note: Clinical giveaway is Ascites, which is an excess amount of water in the peritoneal cavity.

a decreased synthetic capacity of the liver, which includes a low A/G ratio with decreased plasma albumin levels, coagulopathies

Almost all serum protien are produced by liver. C an cause bleeding and Ascites

Cupric ions (Cu2+) in an alkaline medium form a purple color (540 nm) as they interact with peptide bonds

1) NaOH for alkalinity,

2) NaK tartrate,

3) Potassium Iodide (KI),

4) CuSo4

rapid, approximate range of total protein concentration. This method measures the refractive index.

Coomassie blue in acidic solution. When the dye binds the protein, the absorbance increases at 595 nm.

Do NOT dilute urine for proteins. You dilute for creatinine. Only smaller proteins can pass through the glomeruli, but they are VERY likely to be reabsorbed

There can be a lot of false positive results

Notes: They use tetrabromphenol blue at pH of 3,

Turbidimetric methods precipitate (denature) proteins with sulfasalicylic acid (SSA), trichloroacetic acid, or benthonium chloride. SSA is known to precipitate many substances and cause false positive results

it is the deficient enzyme

Leads to a build up of HGA in body tissues

Autosomal recessive

darkening of body tissues due to HGA

Diapers stain black because of HGA in the urine of babies

Defect in Amino Acid transport system, NOT a metabolic deficiency

Kidneys are unable to reabsorb the divalent amino acids (cystine, lysine, arginine, ornithine)

Cystine can result in kidney stones, which can cause flank pain and hematuria

“Mousy” or “Musty” urine odor, eczema, fair complexion

note: Causes mental retardation if not corrected early in life

Can be controlled with PKU-free diet

Brain damage occurs with cessation of a PKU-free diet

Urea nitrogen - ~45% of NPN in the blood

Uric acid - ~20% of NPN in the blood

Creatinine - ~5% of NPN in the blood

Ammonia will be covered later - ~0.2% of NPN in the blood

BUN (mg/dL) x 2.14 = Urea (mg/dL)

BUN is inversely correlated with glomerular filtration rate and renal plasma flow

usually caused by dehydration, but can be due to any reason for impaired blood flow to the kidneys or increased protein catabolism

Acute renal failure

Obstructive Renal Disease

BUN Reference Range

7-18 mg/dL

24 hour urine 12-20 grams/24 hours

BUN is stable at RT for 4 hours

Several days at 4˚C

Several months at -20˚C

Males are slightly higher, but it is not clinically significant

ratio is indicative of prerenal azotemia: dehydration, heart failure

ratio can be seen in intrarenal azotemia, dialysis, SIADH, low protein diet, diarrhea

postrenal azotemia (causes of decreased GFR, like congestive heart failure, obstructive renal cell carcinoma, dehydration, etc.)

note:BUN is usually 15 times that of creatinine don’t use on normal patients.

37.3= prerenal

note: Remember a BUN/Cr 10-20 is usually a renal etiology, BUN/Cr >30 is usually prerenal renal failure unless proven otherwise, BUN/Cr >40 is definitely prerenal

15= postrenal

note: Remember a BUN/Cr 10-20 is usually a renal etiology, BUN/Cr >30 is usually prerenal renal failure unless proven otherwise, BUN/Cr >40 is definitely prerenal

creatinine is secreted ever-so-slightly in the distal convoluted tubule (DCT)

In renal disease, creatinine excretion is decreased

Jaffe Reaction - Creatinine and Picric Acid in alkaline solution

Beware! Picric acid is explosive!

Interferences with protein, glucose, uric acid, ascorbic acid, acetone, ketoacids, cephalosporins

Enzymatic methods are also available which all start with creatininase

0.9-1.2 mg/dL men

0.6-1.1 mg/dL for women

usually increased production of Uric Acid

HGPRT deficiency which results in elevated levels of Uric Acid. Symptoms include mental retardation, muscle fasciculations, Self-mutilation

Tumor-Lysis Syndrome, the rapid killing of cells results in DNA damage, and the production of lots of Uric Acid

Cancer can lead to rapid formation of cells, but they often die off quickly, resulting in DNA damage and release of Uric Acid into the serum

Urea and Creatinine

Results from Renal failure

Neurotoxic

Elevated levels of Uric Acid in the blood, can cause Uremic Frost on a patient’s skin

Prerenal azotemia

Ratio of 35.7 not full diagnositic need over 40

Renal azotemia

Ratio of 18: in ratio

Postrenal azotemia

Ratio of 17.8 why this is post is because of the prostate vs the kidney

the glutamate dehydrogenase method

It measures the diminishing concentration of NADP at 340
nm

This sample must be tested immediately, no waiting. The sample should be venous blood, collected in EDTA or Heparin, and placed on ice

Liver failure → ↑NH3 → neuronal destruction → hepatic encephalopathy

The result is fulminant liver failure and many patients don’t survive the ordeal. Blood ammonia levels are the preferred lab test in this scenario, because they are most closely associated with prognosis and survival

Note: The connection that I want you to make with this is that whenever you hear of a child taking aspirin for a viral illness

urea cycle enzyme disorders

A sequence of amino acid chains.

Hydrogen bonding of the peptide back bone cause the amino acids to fold into a repeating pattern.

three-dimensional folding patter of a protein due to side chain reactions

Protein consisting of more than one amino acid chain.