Plasma Proteins Flashcards
Serum vs Plasma
Serum - liquid part of blood after coagulation - has no clotting factors like fibrinogen
Plasma - liquid, cell free part of bloof that has been treated with anti-coagulants
Serum= plasma - fibrinogen
Where are plasma proteins synthesised?
In the liver w the exception of immunoglobulins
Plasma proteins functions?
-Transport
-Maintaining plasma oncotic pressure
-Buffering pH changes
-Defence Mechanisms
-Coagulation and Fibrinolysis
-Miscellaneous specialised functions
Breakdown of 3 major fractions of plasma proteins?
-Albumin (60-70%)
-Globulins (38%) - alpha1-globulin(5.3%), alpha2-globulin(8.6%), ß-globulin(13.4%), gamma-globulin (11%)
-Fibrinogens (4%)
-Other proteins (<1%)
How are plasma proteins measured?
- Quantitative- measurement of specific protein
- Semi-quantitiave - measured by electrophoresis where types of porteins separated into diff bands
- Measurement of biological activity
4: Immunoassays
What do most diseases that alter plasma proteins affect?
-the synthesis of proteins in the liver
-the distribution of proteins
-their rate of catabolism
their rate of excretion
Albumin structure and where is it produced?
Albumin (69kDa), single polypeptide chain having 585 aa is the most abundant protein (60-70%) in the blood plasma (36-47g/L)
Synthesised in liver - half life in plasma 2-3 weeks
Serum albumin conc is used to assess liver function
What molecules does albumin bind to and transport?
-Metal ions: calcium and copper
-Free fatty acid: albumin binds to free fatty acid released by adipose tissue and facilitates their transfer to other tissues
-Bilirubin: this protects from the toxic side effects of unconjugated bilirubin
Bile acid: albumin carried the bile acids that are recycled from the intestine into the liver in the hepatic portal vein
Functions of Albumin?
Transport
Maintenance of osmotic pressure - form of osmotic pressure exerted by proteins in blood plasma that usually tends to pull water into the circulatory system -large plasma proteins cant easily cross through the capillary walls
-when plasma proteins reduced- proteinuria or malnutrition - reduction of osmotic pressure - fluid retention intissues
What causes an abnormality in the synthesis of albumin?
hereditary defects, liver disease, malnutrition, malabsorptive disease
What causes abnormal distribution of albumin?
Increased capillary permeability- leakage of proteins into extravascular fluid
What causes abnormal catabolism of albumin?
Increased albumin breakdown as a result of injury or infection
What causes abnormality in the removal of albumin?
In non-diseased states little or no albumin is excreted - increased losses may occur through the kidney, GIT or skin (burn victims)
Example of an alpha1-globulin?
alpha1- anti- trypsin
Several allelic genes code for this -pi(phenotype), MM(normal), MS(heterozygous), ZZ or SS(homozygous)
-individuls w this have higher incidence of pulmonary emphydsema and hepatic disorders
-increased levels occur in pregnancy
How does alpha1 anti trypsin affect the lungs?
-5% emphemysa is due to deficiency of this
-Associated w lung infection and increase in activity of macrophage to produce elastase that damages the lung tissues
-smoking can inactivate this globulin
How does alpha1 anti trypsin affect the liver?
-aggregates to form polymers cause liver damage followed by accumulation of collagen resulting in fibrosis and ciarrhosis
Types of alpha2 globulins?
Alpha 2 macroglobulins
Haptoglobins
Caeuroplasmin
Alpha-fetoprotein
What do alpha2-macroglobulins do?
-major alpa2 globulin
-binds and inactivates endopeptidases such as trypsin
-increased nephrotic syndrome - some times cirrhosis
What do haptogloblins do?
-Bind Hb to form HbHp complexes
-Func to conserve iron stores in the body
-Decreased levels in intravascular haemolysis, liver disease
-Increased in acute infection, nephrotic syndrome
What do caeuroplasmin do?
-Copper
containing protein binds approx 90%
-Reduced in Wilsons disease (genetic disease that disrupts copper transport in body), malnutrition and nephrotic syndrome
-Increased levels in pregnancy and in women on oral contraceptives
What does alpha-fetoprotein do?
-Protein present in tissue and plasma of foetus
-Ultra-sesnitive immunoassays allow for the detection of minute amounts in adults
-Approx 50% of cases of hepatocellular carcinoma present w gross increases of alphja- FP levels
Examples of ß globulins?
Transferrin - principle plasma transport protein for iron
-Complement proteins - consists of atleast 20 proteins in blood
Abnormalities in transferrin?
-Atransferrinaemia- rare congenital deficiency of transferrin
-Acquired transferrin deficiency is a negative APP- Acute pase protein- and low conc are seen in inflammation and malignancy
-increased levels seen in iron deficiency states
What do complement proteins interact with?
1) sequentially w Ag-Ab complexes
2) with one another
3) with cell membranes
in a complex but adaptable way to destroy viruses and bacteria
