Overview of Plasma Proteins: Structure, Function, and Testing

Human Proteome

~20,000 protein-coding genes in humans.

Proteins

Macromolecules made of amino acids linked by peptide bonds.

Plasma Proteins

Most produced in liver; exceptions include immunoglobulins.

Immunoglobulins

Antibodies secreted by plasma cells, not liver.

Hormones

Regulate synthesis and breakdown of plasma proteins.

Peptide Bonds

Covalent bonds linking amino acids, releasing water.

Protein Structure

Levels: primary, secondary, tertiary, quaternary.

Primary Structure

Linear sequence of amino acids in a protein.

Secondary Structure

Polypeptide chains form coils, helices, or sheets.

Tertiary Structure

3D folding of polypeptide chains.

Quaternary Structure

Interaction of multiple peptide chains in a protein.

Simple Proteins

Composed solely of amino acids.

Conjugated Proteins

Contain non-protein groups attached to protein.

Apoproteins

Proteins without their non-protein groups.

Apolipoprotein

Protein remaining after lipid removal from lipoprotein.

Chromoprotein

Protein with a pigment, e.g., hemoglobin.

Metalloprotein

Contains metal ions, e.g., ceruloplasmin.

Glycoprotein

Protein with carbohydrate groups, e.g., mucin.

Lipoproteins

Complexes of lipids and proteins.

Nucleoproteins

Proteins combined with nucleic acids (DNA/RNA).

Serum Total Protein (TP)

Measured nitrogen balance; normal range 6.2-8.3 g/dL.

Plasma vs Serum

Plasma contains fibrinogen; serum does not.

Heparin Anticoagulant

Used to prevent blood clotting in plasma.

Hyperproteinemia

Elevated total protein levels in serum.

Dehydration

Loss of body water affecting protein concentration.

Multiple Myeloma

Cancer causing increased gamma-globulins in serum.

Hypoproteinemia

Decreased total protein levels in serum.

Kwashiorkor

Protein deficiency causing malnutrition in children.

Nephrosis

Kidney disorder leading to protein loss in urine.

BUN

Blood urea nitrogen; elevated in kidney dysfunction.

Prealbumin

Transport protein for thyroid hormones; short half-life.

Total Parenteral Nutrition (TPN)

IV nutrition for patients unable to eat.

Colloidal Osmotic Pressure

Pressure exerted by proteins in blood plasma.

Osmotic Pressure

Pressure that drives fluid movement across membranes.

Edema

Excess fluid accumulation in interstitial spaces.

Hypoalbuminemia

Low albumin levels indicating various health issues.

Hyperalbuminemia

Elevated albumin levels, often due to dehydration.

Albumin

Most abundant serum protein; maintains osmotic pressure.

Transferrin

Iron transport protein in blood plasma.

C-Reactive Protein

Marker for inflammation in the body.

Ceruloplasmin

Copper-carrying protein; involved in iron metabolism.

Fibrinogen

Protein essential for blood clotting.

Alpha-Fetoprotein

Protein produced by the liver; tumor marker.

Clinical Correlation

Linking lab results to patient health status.

Protein

Total protein concentration in blood, measured in g/dL.

Albumin

Main protein in blood plasma, maintains oncotic pressure.

Prealbumin

Indicator of nutritional status, measured in mg/L.

A/G Ratio

Albumin to globulin ratio, indicates protein balance.

Globulins

Group of proteins in blood, includes four fractions.

Alpha-1-Antitrypsin (A1AT)

Inhibits enzymes causing tissue damage, acute phase reactant.

Congenital A1AT Deficiency

Genetic condition linked to early-onset emphysema.

Serum Protein Electrophoresis

Technique to separate proteins based on size and charge.

Haptoglobin

Binds free hemoglobin, evaluates hemolytic anemia.

Ceruloplasmin (CER)

Copper transport protein, positive acute-phase reactant.

Wilson's Disease

Autosomal recessive disorder causing copper accumulation.

Kayser-Fleischer Ring

Copper deposits in cornea, indicative of Wilson's Disease.

Alpha-fetoprotein (AFP)

Fetal protein, tumor marker for liver and germ cell cancers.

Neural Tube Defects

Congenital malformations detectable by elevated AFP.

Emphysema

Lung condition characterized by damaged alveoli.

Acute Phase Reactants

Proteins that increase during inflammation or injury.

Proteinuria

Presence of excess protein in urine, indicates kidney issues.

Generalized Edema

Swelling due to fluid accumulation in tissues.

Ascites

Fluid buildup in abdominal cavity, often due to liver disease.

Increased Urine Copper

Sign of Wilson's Disease, indicates copper metabolism disorder.

Liver Biopsy

Procedure to diagnose liver conditions, including Wilson's Disease.

Computed Tomography (CT) Scan

Imaging technique to visualize internal structures, like lungs.

Chronic Inorganic Dust Exposure

Long-term inhalation of dust, risk factor for lung disease.

Conjugated hyperbilirubinemia

Elevated bilirubin due to liver dysfunction.

Severe coagulopathy

Increased bleeding risk from clotting factor deficiencies.

Tremors

Involuntary muscle contractions at rest or during action.

Kayser-Fleischer rings

Copper deposits in the cornea, indicative of Wilson's disease.

Sunflower cataracts

Copper accumulation causing characteristic eye lens changes.

Ceruloplasmin

Copper-carrying protein; low levels indicate copper metabolism issues.

Serum protein

Total protein concentration in blood; normal range 6.4-8.3 g/dL.

Serum albumin

Main protein in blood; low levels indicate liver dysfunction.

Alanine transaminase (ALT)

Liver enzyme; elevated levels indicate liver damage.

Aspartate transaminase (AST)

Enzyme indicating liver or muscle injury; elevated levels.

Alkaline phosphatase (ALP)

Enzyme associated with liver and bone disorders; elevated levels.

Bilirubin

Breakdown product of hemoglobin; elevated levels indicate liver issues.

α2-Macroglobulin

Inhibits proteases; increased in nephrosis.

Transferrin (TF)

Iron transport protein; levels increase with iron deficiency.

β-Globulins

Group of proteins including transferrin and β-microglobulin.

β2-Microglobulin (BMG)

Protein indicating tumor burden in malignancies.

Complement C-3

Part of immune system; increased in inflammation.

Fibrinogen

Clotting factor; increased during inflammation and liver disease.

C-Reactive Protein (CRP)

Inflammation marker; rises with infections and inflammation.

hs-CRP

High-sensitivity CRP; assesses cardiac risk.

Immunoglobulins

Antibodies produced by plasma cells in immune response.

Acute phase reactants

Proteins that change in response to inflammation.

Reticuloendothelial system (RES)

Part of immune system involved in iron storage.

Immunoglobulins (Igs)

Antibodies classified into five distinct classes.

Polyclonal increase

Normal immune response to inflammation or infection.

Monoclonal increase

Single clone produces one specific immunoglobulin.

IgG

Most abundant immunoglobulin in serum, four subclasses.

IgM

5-10% of circulating immunoglobulins.

IgA

10-15% of circulating immunoglobulins.

IgE

Trace levels, associated with allergic reactions.

IgD

Trace levels, function remains unknown.

Cryoglobulins

Proteins that precipitate in cold temperatures.

Total Nitrogen

Measures all chemically bound nitrogen in a sample.