L.5 Serum proteins Flashcards
What is plasma?
Noncellular component of anticoagulated whole blood
Plasma serves as the liquid medium for blood cells and contains various proteins and nutrients.
What are plasma proteins?
All proteins of blood plasma and interstitial fluid
Intersitial fluid is found between blood vessels and cells.
Which is the most abundant plasma protein?
Albumin
Other plasma proteins include immunoglobulin, transport proteins, and clotting proteins.
Where are most plasma proteins synthesized and catabolized?
In the liver
What can cause alterations to serum total protein?
- ↑ or ↓ in volume of plasma water
- ↑ or ↓ in concentration of protein in plasma
These alterations are due to intake, synthesis, excretion, and distribution.
What is the reference range for total serum protein?
(65 - 85 g/L)
What does hypoproteinaemia indicate?
Haemodilution
What does hyperproteinaemia indicate?
Haemoconcentration
What are methods for determination of total protein?
• Direct photometric methods
• Biuret method
• Dye-binding methods
• Turbimetric and nephelometric methods
What is the principle of direct photometric methods?
Proteins can absorb UV light between 200-230 and 272-290nm
What is the Warburg-Christian method?
Natural absorbance of proteins
At what wavelength does absorption due to peptide bond backbone occur?
205nm
What is the sensitivity comparison between 205nm and 280nm?
Higher sensitivity at 205nm
What causes high protein-to-protein variation in UV absorption?
Proportion of tryptophan, tyrosine, and phenylalanine varies greatly
What substances interfere with UV light absorption at 280nm?
Free tyrosine and tryptophan, uric acid, and bilirubin
What is the Biuret method?
Peptide bonds react with Cu2+ ions in alkaline solutions to form a coloured product
At what wavelength is absorbance measured in the Biuret method?
540nm
What does a blue color indicate in the Biuret method?
Proteins are absent
What does a purple color indicate in the Biuret method?
Proteins are present
What are dye-binding methods based on?
Ability of proteins to bind dyes such as Coomassie brilliant blue
What is the linear range for dye-binding methods?
Up to 150mg/dL
What methods utilize dye-binding for protein determination?
• Serum protein electrophoresis
• Bence-Jones proteins in urine
What does turbidimetry measure?
Intensity of transmitted light
Turbidimetry is used to assess the clarity of a solution by measuring how much light passes through it.
At what angle does the detector read in turbidimetry?
180 degrees from the incident light beam
This configuration allows for the measurement of transmitted light intensity.
What do nephelometers measure?
Intensity of scattered light
Nephelometry is often used to analyze low concentration proteins.
At what angle does the detector read in nephelometry?
Right angle from the incident light beam
This setup is critical for measuring scattered light effectively.
Which method is better for low concentration proteins?
Nephelometric methods
Although more expensive, they provide better accuracy for low concentrations.
What are the methods for total globulin determination?
- Colourimetric methods
- Globulin differential (albumin-globulin ratio)
- Electrophoresis
- Immunochemical methods
These methods help in quantifying globulin levels in serum.
What is the preferred method for determining globulin?
Globulin differential (albumin-globulin ratio)
This method involves calculating globulin as Total Protein minus Albumin.
What does serum protein electrophoresis (SPEP) measure?
The protein content of biological fluids
SPEP is commonly used for serum, urine, and cerebrospinal fluid (CSF).
How does electrophoresis separate particles?
Based on mass to charge ratio
This separation helps identify abnormalities in protein levels.
What type of sample is needed for serum protein electrophoresis?
Serum (with removal of fibrinogen)
Fibrinogen can interfere with electrophoresis results.
What is the most abundant plasma protein?
Albumin
Albumin plays a crucial role in various physiological functions.
What is the molecular weight of albumin?
≈68 kDa
This size contributes to its function and behavior in biological fluids.
What is the reference range for albumin levels?
(35-50 g/L)
Maintaining albumin levels within this range is critical for health.
What percentage of total plasma protein does albumin represent?
≈60%
Albumin is a major component of plasma proteins.
What is the half-life of albumin?
≈18-20 days
This relatively long half-life is important for its function in circulation.
What is the fastest migrating protein in serum protein electrophoresis?
Albumin
Its charge and size allow it to migrate rapidly in an electric field.
Where is albumin synthesized?
Liver
Albumin constitutes about 25% of total hepatic protein synthesis.
What are the roles of albumin? List them.
- Transport of ligands (e.g. amino acids, hormones)
- Colloidal osmotic pressure maintenance
Albumin is essential for transporting various substances in the blood.
What percentage of osmotic pressure in human plasma is albumin responsible for?
75-80%
This role is crucial for maintaining blood volume and fluid distribution.
What condition can hypoalbuminaemia lead to?
Retention of fluid in tissue (oedema)
Low albumin levels can cause swelling and fluid accumulation in tissues.
What is hypoalbuminaemia?
A condition characterized by low levels of albumin in the blood.
It can lead to various health issues due to reduced oncotic pressure and other functions of albumin.
What can cause hypoalbuminaemia?
- Liver cirrhosis
- Nephrotic syndrome
- Malnutrition
- Burns
- Analbuminaemia
Each cause affects albumin production or leads to its loss in the body.
How does liver cirrhosis lead to hypoalbuminaemia?
Hepatocyte damage leads to impaired protein production.
What is nephrotic syndrome?
A kidney condition that increases the permeability of the glomerular basement membrane, leading to massive proteinuria and loss of albumin in urine.
How does malnutrition contribute to hypoalbuminaemia?
Lack of dietary protein prevents sufficient albumin synthesis by the liver.
What effect do severe burns have on albumin levels?
Severe burns cause capillary leakage, leading to loss of albumin into the interstitial space.
What is analbuminaemia?
A rare congenital disorder caused by a genetic mutation leading to almost complete absence of albumin.
What are the effects of hypoalbuminaemia?
- Oedema
- Increased infection risk
- Hyperlipidaemia
- Shock
- Delayed wound healing
These effects result from the essential roles of albumin in maintaining oncotic pressure, immune transport, and tissue repair.
What condition can lead to hyperalbuminaemia?
Fluid depletion or dehydration.
What is a dye-binding method for albumin determination?
Bromocresol Green, which is known to slightly overestimate albumin.
What are some proteins produced in the liver?
- Albumin
- A and B globulins
- A-1-Antitrypsin
- Haptoglobulin
- Transferrin
- C-reactive Protein (CRP)
Y-globulins are synthesized by plasma cells and B cell precursors.
What type of inhibitor is A-1-Antitrypsin?
Serine protease inhibitor (serpin)
Which enzyme does A-1-Antitrypsin inactivate?
Leucocyte elastase
What condition can result from A-1-Antitrypsin deficiency?
Emphysema
Where is A-1-Antitrypsin synthesized?
In the liver
What is the risk associated with A-1-Antitrypsin deficiency?
Increased risk of emphysema
What lifestyle factor increases the risk associated with A-1-Antitrypsin deficiency?
Smoking
What is the major function of Haptoglobin?
Binds free haemoglobin
Where is Haptoglobin synthesized?
In the liver
What condition is Haptoglobin associated with?
Intravascular haemolysis
What happens to Haptoglobin levels during intravascular haemolysis?
Sudden drop in levels
When does haematuria occur in relation to Haptoglobin?
Once Haptoglobin is depleted in IVH
In which conditions is Haptoglobin decreased?
Most forms of liver disease
What is the major role of Transferrin?
Transport protein for iron
What are the two main destinations for the iron transported by Transferrin?
- To cells for incorporation in myoglobin, cytochromes, haemoglobin
- To liver for storage
In which region does Transferrin migrate?
β region (β-1 globulin)
Where is Transferrin synthesized?
In the liver
How is Transferrin used in the diagnosis of anaemia?
Trf increased in IDA and normal or decreased in anaemia of chronic disease
What happens to Transferrin levels in haemochromatosis?
Transferrin levels are down and serum iron levels are increased
What is C-Reactive Protein (CRP)?
An early positive Acute Phase Reaction protein
CRP is involved in the inflammatory response.
What does Acute Phase Reaction (APR) involve?
Changes in plasma proteins (↓ or ↑)
APR is a response to inflammation.
What is the primary use of CRP?
As a biomarker of inflammation
It is extensively used in clinical settings.
Where is CRP synthesized?
In the liver
What conditions cause a dramatic rise in CRP levels?
Stress & trauma, infection, inflammation, surgery, burns, neoplasms
Bacterial infections cause more dramatic elevation than viral infections.
What are the basal levels of CRP?
Less than 10 mg/L
What can cause naturally slightly elevated CRP levels?
Mildly/chronic inflammatory conditions such as diabetes, periodontitis, smoking, obesity, pregnancy
What is the γ-globulin region associated with?
Immunoglobulins
What role do immunoglobulins play in the body?
Key role in defense mechanisms
How many types of immunoglobulins are there?
Five types: IgG, IgA, IgM, IgD, IgE
When is the synthesis of gamma globulins increased?
In chronic infections, chronic liver diseases, autoimmune diseases, leukaemias, lymphomas, and various other malignancies
What is Hypoalbuminaemia?
A condition characterized by low albumin levels
What is Hyperalbuminaemia?
A condition characterized by high albumin levels
What is Multiple Myeloma?
A cancer of the immune system involving β-lymphocyte proliferation (plasma cells)
Typically a disease of older patients.
What is over-secretion of non-functional immunoglobulin called?
Paraprotein
What are paraproteins referred to as monoclonal?
Because they are identical clones of a single plasma cell
What family of neoplasms does Multiple Myeloma belong to?
Monoclonal gammaopathies
