SN6
SHORT NOTE
5M
Enumerate the plasma proteins with their normal values and describe their functions.
Normal Values
| Protein | Concentration | Molecular weight |
|---|---|---|
| Total plasma protein | 6–8 g/dL | — |
| Albumin | 3.5–5.5 g/dL | 69,000 |
| Globulins | 2–3.5 g/dL | 90,000–1,300,000 |
| Fibrinogen | 0.2–0.4 g/dL | 340,000 |
| A:G ratio | 1.7:1 to 2:1 | — |
Site of Synthesis
- Liver — all albumin, fibrinogen, and α and β globulins
- Plasma cells (lymphoid tissue) — γ globulins (immunoglobulins)
- Reticuloendothelial system — small contribution
Functions
- Colloid osmotic (oncotic) pressure — 25 mmHg; albumin contributes 80% because of its high concentration and low molecular weight
- Transport — albumin carries bilirubin, fatty acids, calcium, drugs; specific globulins carry iron (transferrin), copper (caeruloplasmin), Hb (haptoglobin), hormones
- Coagulation — fibrinogen and other clotting factors
- Immunity — γ globulins are antibodies
- Buffering — contribute about 15% of blood buffering capacity
- Viscosity — maintain blood viscosity and hence blood pressure
- Reserve protein — mobilised in starvation
- ESR — fibrinogen and globulin promote rouleaux formation
Separation Methods
- Electrophoresis — separates into albumin, α1, α2, β, γ fractions
- Salting out with sodium sulphate; ultracentrifugation; chromatography
Variations
| Change | Causes |
|---|---|
| Hypoproteinaemia | Nephrotic syndrome (albumin lost in urine), liver failure, malnutrition, burns, protein-losing enteropathy |
| Hyperproteinaemia | Dehydration, multiple myeloma (γ globulin), chronic infection |
| Reversed A:G ratio | Cirrhosis, nephrotic syndrome, myeloma, kala-azar |
Applied Aspects
- Oedema appears when albumin falls below about 2.5 g/dL
- Kwashiorkor — protein malnutrition → hypoalbuminaemia → oedema and ascites
- Albumin is the best single index of chronic liver function (half-life 20 days); prothrombin time reflects acute function
All questions in Blood (haematology)
- Q1Define erythropoiesis. Describe its sites, stages, and the factors regulating it. Add a note on the fate of red blood cells. ★
- Q2Describe the mechanism of blood coagulation. Explain the intrinsic and extrinsic pathways and the tests used to assess them. Add a note on natural anticoagulants. ★
- Q3Classify blood groups. Describe the ABO and Rh systems and discuss mismatched transfusion reaction. Add a note on erythroblastosis fetalis. ★
- Q4Classify leucocytes and give their normal values. Describe the functions of neutrophils and discuss the types of immunity. ★
- Q5Describe the structure and types of haemoglobin. Outline its synthesis and describe its fate after red cell destruction. ★
- SN1Describe the formation and functions of platelets. ★
- SN2Classify anticoagulants. Describe the mechanism of action of heparin and warfarin. ★
- SN3Define ESR. Give its normal values and enumerate the factors affecting it. ★
- SN4Define anaemia. Classify it morphologically and aetiologically. ★
- SN5Describe bilirubin metabolism. Classify jaundice and give the findings in each type. ★
- SN6Enumerate the plasma proteins with their normal values and describe their functions.
- SN7Write a short note on haemophilia.