Proteins Flashcards
What two processes reflect the resulting protein concentration?
Protein concentrations (plasma or serum) reflect balance between anabolism and catabolism.
What body fluids are typically measured for their protein content?
Serum, urine and CSF total protein are measured in the lab.
What are the reference ranges for total protein for plasma, urine and CSF?
Plasma: 60 - 80 g/L
Urine: < 0.14 g/L
CSF 0.20-0.40 g/L
Where are most proteins synthesized?
Most proteins at synthesized in the liver, with the exception that immunoglobulins are produced by lymphocytes.
What protein represents the largest fraction and by ~ how much?
Albumin is the largest fraction of total protein at ~60%.
Where is albumin synthesized?
Liver
What functions does albumin serve (5)?
- Main transporter of insoluble organic anions.
- Binding of toxic heavy metal ions,
- Transport of excess quantities of poorly soluble hormones.
- Maintenance of serum osmotic pressure, and
- Provision of a reserve store of protein.
What does the glomerular basement membrane do?
Ultrafilter allows only small molecules to pass through.
What occurs if the glomerular basement membrane is damaged?
Albumin increases in the urine. Degree of damage reflected in size of urinary proteins.
What is proteinuria?
Presence of protein, usually albumin, in urine. Also known as: albuminuria.
- Proteins pass through glomerulus of kidney.
- Not re-absorbed by renal tubules.
What is the implications of finding protein in urine?
Small amount so protein in normal urine does not always indicate renal disease. - Need to investigate cause.
- Could be the result of strenuous exercise for example.
What is the test of choice when screening for albuminuria?
Random urine to creatinine ratio is the test of choice when screening for albuminuria. Early indication of glomerular dysfunction.
What is microabluminuria?
Small excretion of albumin in urine.
What is overtnephropathy?
Persistent high levels of albumin in urine.
What types of reference ranges are there for albumin?
Plasma (33-45 g/L)
Urine (24 hours) < 30 mg/day
Urine (Random) Male < 2.0 mg/mmol creatinine.
Urine (Random) Female < 2.8 mg/mmol creatinine.
What disease states result in an increase in CSF proteins?
Meningitis, hemorrhage, tumors, Multiple Sclerosis, diabetes, etc.
What condition could cause a decrease in CSF proteins?
Decrease in CSF proteins could be related to a leakage from the CNS.
What are some testing methods used for total protein analysis on CSF?
Chemistry analyzer and electrophoresis.
Purpose: To identify specific proteins.
What is oligoclonal banding?
Oligoclonal banding is representative of the presence of inflammation. Appearance of multiple bands in gamma region on electrophoresis of CSF that are not present in serum is indicative of local synthesis of immunoglobulins (IgG).
What disease state does one expect to see oligoclonal banding appear in the electrophoresis analysis that is not present in serum?
Multiple Sclerosis.
It is typical for MS to have two discrete oligoclonal bands in the CSF.
What is the reference range and critical value for total proteins of CSF?
Reference range: 0.20-0.40 g/L
Critical value of CSF Protein is > 1.9 g/L
Too high of CSF protein is life threatening.
What does alpha1-antitrypsin do?
- Inhibition of neutrophil elastase.
2. Released during infection but causes damage if not inhibited.
When and why is maternal AFP screening performed?
Maternal AFP screen is looking for alpha1-fetoprotein between 15 and 20 weeks of gestation.
Elevated levels may indicate spina bifida or neural tube defects.
Low levels may indicate Trisomy 21 or Trisomy 18.
Where does alpha1-fetoprotein (AFP) come from?
Synthesized in fetus and decreased after birth.
What does the protein haptoglobin do?
- Functions to bind hemoglobin.
2. Allows iron to be recycled.
What conditions are increased and decreased levels of haptoglobin related to?
Increased: Inflammatory conditions.
Decreased: Red cell breakdown.
What is the purpose of the ceruloplasmin protein?
- Binds 90% of serum copper.
- Enzymatic activities.
It is an acute phase protein.
What conditions are the increased and decreased levels of ceruloplasmin protein related to?
Increased: Inflammation.
Decreased: Wilson’s disease (if not bound to copper it degrades; excess copper is deposited in tissues like the liver).
What function does the protein transferrin serve?
Binds iron for transport to storage sites like the liver.
What is the function of lipoproteins?
Transports cholesterol, triglycerides, and phospholipids in the bloodstream (HDL and LDL).
What is the function of complement proteins?
Participates in immune reaction.
What type of disease state are complement proteins associated with?
Linked to inflammatory disease.
What is the function of the protein fibrinogen?
Functions to form a fibrin clot when activated by thrombin.
What disease condition is the protein C-Reactive Protein associated with?
Increased in inflammatory disease.
Note: There is a debate about measuring CRP as it is released for many diseases and hence is non-specific, but still requested at times.
Where is the protein myoglobin found?
Found in striated skeletal or cardiac muscles. It is a heme protein.
What happens to myoglobin when there is damage to the muscle?
It is released with damage.
What is troponin a complex of?
Complex of three proteins that function to regulate cardiac muscle contraction:
- Troponin T (cTnT)
- Troponin I (cTnI)
- Troponin C (TnC)
What is the troponin complex proteins sensitive indicators of?
The three proteins are often measured separately for a myocardium infarction. They are sensitive indicators of even small amounts of cardiac damage, in particular Troponin I.
When are newborn screening card specimens taken and why?
- They are collected no sooner than 24 hrs after birth and aim to be collected no later than up to 5 days of age.
- The reason for no sooner than 24 hrs is so that the baby’s own body is given a chance to support itself (just out of Mom). If later than 5 days then if the baby had one of the conditions of concern it could start to be detrimental to the baby.
What types of diseases are screened for in Manitoba’s Newborn screening program?
- Metabolic and endocrine dysfunction that can be caused by enzyme defects, abnormal metabolism of proteins/carbs/fats, gene defects, etc.
- Disease found w/in population shortly after birth that can be treated.
What are the impacts of a block in the metabolic pathway for an infant?
- Block in metabolic pathway –> results in build-up of substance before the block.
- Deficiency of products after the block
- -> abnormal metabolism.
- Symptoms may include:
a) failure to thrive.
b) Abnormalities in features, hair or skin.
c) Behavioral and learning problems.
What enzyme is lacking in the disease PKU and what was it suppose to do?
- Absence of phenylalanine hydroxylase (PAH).
2. Normally converts phenylalanine to tyrosine.