biochem 3

What are the building blocks of proteins?

Amino acids

A single amino acid contains at least 1 of what two groups?

One amino group & one carboxyl group

What is a chain of amino acids called?

Polypeptide

What is a large polypeptide called?

Protein

How many amino acids can be synthesized by the body? And what are they called?

10; nonessential

What are the 10 essential amino acids?

\-Phenylalanine
\-Valine
\-Threonine
\-Tryptophan
\-Isoleucine
\-Methionine
\-Histidine
\-Arginine
\-Leucine
\-Lysine

What are the 10 nonessential amino acids?

\-Alanine
\-Asparagine
\-Aspartic acid
\-Cysteine
\-Glutamic acid
\-Glutamine
\-Glycine
\-Proline
\-Serine
\-Tyrosine

What are inherited enzyme defects that inhibit metabolism of certain amino acids?

Aminoacidopathies

What is the disease with the absence of activity of phenylalanine hydrolase (PAH) and is autosomal recessive, 1 in 15,000?

Phenylketonuria (PKU)

What can phenylketonuria cause?

Brain damage, delayed mental development, microcephaly

The Phe/Try (phenylalanine/tyrosine) ratio improves the specificity for diagnosing what deficiency?

Phenylketonuria

What is found in the blood and urine of PKU patients? Urine has a musty or mousy odor.

Phenylalanine & metabolites

What semi-quantitative bacterial inhibition assay for phenylalanine was used historically? If sample contains phenylalanine, bacteria will grow.

Guthrie test

What has replaced the Guthrie test?

HPLC, MS/MS, microfluorometric assay on dried blood filter discs

What ratio can be helpful in diagnosing PKU?

Phe/Tyr, increased phenylalanine and decreased tyrosine

What inherited autosomal recessive aminoacidopathy is characterized by excretion of tyrosine in urine?

Tyrosinemia

Describe the 3 types of tyrosinemia.

Type I: 1 in 100,000 - liver/kidney failure, CNS issues, usually do not live past age 10. Caused by mutation in fumarylacetoacetate hydrolase (FAH) gene - required for metabolism of tyrosine
Type II: 1 in 250,000
Type III: Very rare

What inherited autosomal recessive aminoacidpathy, 1 in 250,000,
is characterized by a mutation in gene which leads to deficiency in enzyme homogentistate oxidase (HGD) which leads to elevation in homogentistic acid (HGA)?

Alkaptonuria

What color will urine turn in alkaptonuria when exposed to air?

Brown-black

What rapid test is used for Alkaptonuria?

Ferric chloride

What autosomal recessive disease, 1 in 185,000, inhibits normal metabolism of leucine, isoleucine, and valine?

Maple Syrup Urine Disease (MSUD)

What characteristic odor of the breath, urine, and skin is in MSUD?

Maple syrup

What can MSUD cause?

Brain injury, muscle rigidity, respiratory irregularities

What tests are used to detect MSUD?

Modified Guthrie, microfluorometric assay, DNA mutation detection

What autosomal recessive disorder, 1 in 200,000, results in mutations in several genes, to include MTHFR and a deficiency in enzyme cystathionine Beta-synthase, which is needed for metabolism of methionine?

Homocystinuria

What autosomal recessive, 1 in 10,000, results in a mutation in SLC3A1/SLC7A9 and causes inadequate reabsorption of cysteine in kidneys?

Cystinuria

What test is used to diagnose cystinuria?

Cyanide nitroprusside

Every function in living cell depends on what?

Proteins

How many amino acids does a typical protein have?

200-300

What is the molecular mass range for proteins?

6,000 to several million

Where does synthesis occur for most proteins?

Liver

What are the 4 levels of protein structures?

primary, secondary, tertiary, quaternary

What is the nitrogen content in serum protein?

16%

What is the pH at which protein has no net charge?

Isoelectric point (pI)

Isoelectric point (pI)

If pH > pI, charge is negative; if pH < pI, charge is positive

What determines solubility?

> charge = > solubility in water

Balance should exist between protein synthesis (anabolism) and what?

Breakdown (catabolism)

Where does catabolism of proteins primarily occur?

Liver

What 4 tests will a specific protein analysis include?

Total protein, albumin, globulins, A/G ratio

How did prealbumin get its name?

It migrates before albumin in a classic SPE

What is critical to transport retinol (Vit A)?

Prealbumin

In what cases would you see increased prealbumin?

Alcohol abuse, steroid therapy, chronic renal failure

In what cases would you see decreased prealbumin?

Nutritional deficiency, hepatic damage, acute phase inflammatory response

What is the most abundant protein in plasma?

Albumin

What is the primary function of albumin?

Capacity to bind and transport various substances in blood (i.e. CA, thyroid hormones, drugs, fatty acids)

What is the reference range for albumin (ALB)?

3\.5-5.5 g/dL

In what cases would albumin be increased?

Acute inflammatory response, liver & kidney disease, malnutrition, malabsorption

In what cases would albumin be decreased?

Dehydration (usually clinically insignificant)

What is the reference range for protein globulins?

2\.5-3.5 g/dL

Total protein is equal to what?

Prealbumin + albumin + globulin

What is the function of alpha-1 antitrypsin (AAT)?

Inhibition of protease neutrophil elastase (PNE)

What is released from neutrophils post infection?

Protease neutrophil elastase

PNE can accumulate leaving damage and lead to what?

Emphysema & cirrhosis

What plasma protein is synthesized in utero by developing embryo/fetus and then by liver?

Alpha1-Fetoprotein (AFP)

In what cases would AFP be increased?

Spina Bifida, Neural Tube Defects, Abdominal Wall Defect, Anencephaly, Twins

In what cases would AFP be decreased?

Trisomy 21 (Downs Syndrome) & Trisomy 18 (Edward's Syndrome)

What plasma protein is synthesized in the liver and is a positive acute phase protein?

Haptoglobin (Hp)

What is the primary function of haptoglobin?

Bind free hemoglobin to prevent loss of iron into urine

How is haptoglobin used to evaluate hemolytic anemia?

Normal levels: anemia due to non-hemolytic causes
Decreased levels: hemolytic anemia

What is primarily measured to aid in diagnosis of Wilson's disease, where it is decreased?

Ceruloplasmin

Ceruloplasmin contains what?

Copper

What percentage of copper is bound to ceruloplasmin?

90%

What plasma protein inhibits proteases and in kidney disorders is increased 10X due to its large size, which inhibits filtration at the renal glomeruli?

Alpha 2 Macroglobulin

What is the primary function of transferrin?

Binds and transports iron to storage site

Increased iron bound to transferrin is found in what disease?

Hemochromatosis

Decreased iron bound to transferrin is found in what diseases?

Liver disease, nephrotic syndrome, infection, inflammation

What beta 2 protein is a light chain component of MHC (HLA)and has a small size, filtered by renal glomerulus, but almost completely reabsorbed and catabolized in proximal tubules?

Beta 2 Microglobulin

Decreases in C3 is associated with what diseases?

Autoimmune disease, bacteremia, chronic hepatitis

Decrease in C4 is associated with what diseases?

Disseminated intravascular coagulation (DIC), acute glomerulonephritis, chronic hepatitis, and SLE

What plasma protein is a natural defense mechanism?

Complement

In what cases would you see an increase in C3 & C4?

Acute inflammatory disease & tissue inflammation

Which plasma protein measurement is debated in replacing the ESR?

C-reactive protein

What plasma protein is one of largest circulating proteins and a positive acute phase reactant that increases quickly in infection and pregnancy?

Fibrinogen

What is one of first acute phase reactants to rise in response to inflammation; very non-specific?

C-Reactive protein

What are two cardiac biomarkers?

Troponin & myoglobin

What is a marker of congestive heart failure, also elevated with MI and patients undergoing renal dialysis?

B-type natriuretic peptide (BNP)

What is used to help predict the short term risk of premature delivery?

Fetal fibronectin

What is a low molecular weight protein (120 aa) - good marker for glomerular filtration and not affected by mass, gender, race, age?

Cystatin C

What is the term for total protein level less than reference range? Why does this occur?

Hypoproteinemia; Occurs in any condition where a negative nitrogen balance exists

What is the term for an increase in total plasma proteins? Why does this occur?

Hyperproteinemia; Occurs in dehydration, when concentration of proteins is elevated due to decreased volume of solvent water

What measures all chemically bound nitrogen in a sample using chemiluminescence?

Total nitrogen

What are three methods for measuring total protein?

Kjeldahl, biuret, dye binding

Which method of measuring total proteins is the classic method which measures the amount of nitrogen in the sample?

Kjeldahl

Which method of measuring total proteins is the most widely use and is based on the principle that in an alkaline medium and the presence of at least 2 peptide bonds, cupric ions will complex with groups involved in peptide bond to form a violet color?

Biuret

What nm is the biuret method measured at?

540 nm

Color proportional to what in the biuret method?

Number of peptide bonds & reflects total protein concentration

Which method of measuring total proteins is based on the ability of most serum proteins binding dyes but can see more variation in results?

Dye binding

What is the most significant finding of SPE?

Monoclonal Ig disease

What allows for further separation of proteins into as many as 12 bands and uses higher voltage, cooling system, and more concentrated buffer?

High-Resolution Protein Electrophoresis

What is the separation of molecules that takes place in silica capillaries?

Capillary Electrophoresis

What is the zone electrophoresis that separates proteins on basis of pI?

Isoelectric Focusing

What is the reaction of protein and antibody is measured by immunochemical assays; referred to as IFE?

Immunochemical Methods

What was traditionally used to monitor renal function?

Nonprotein Nitrogen (NPN) Compounds

Nonprotein nitrogen compounds include what?

\-Uric acid
\-Urea nitrogen
\-Creatinine
\-Ammonia

What NPN compound is present in highest concentration in blood?

Urea

What is a major excretory product of protein metabolism, formed in liver from amino groups and free ammonia generated during protein catabolism?

Urea

Concentration of urea in plasma is determined by what 3 things?

•Protein content of the diet
•Rate of Protein Catabolism
•Renal function and perfusion

What is used to evaluate renal function, hydration status, nitrogen balance, adequacy of dialysis, and aid in diagnosis of renal disease?

Urea

Primates cannot convert uric acid into what?

Allantoin

To translate urea into what do you divide by 2.14?

Nitrogen