plasma-proteins in the bloodstreams.pptx

proteins plasma composition for med students

1. PLASMA PROTEINS

2. FUNCTIONS NUTRITIVE BINDING & TRANSPORT FLUID EXCHANGE BLOOD COAGULATION RESERVE PROTEINS VISCOSITY OF BLOOD BUFFER DEFENCE OF BODY ENZYMES HORMONES

3. 1. NUTRITIVE FUNCTION OF PLASMA PROTEINS Simple proteins and a good source of proteins Macrophages split plasma proteins into amino acids for tissue protein synthesis

4. 2. PLASMA PROTEINS AS RESERVE PROTEINS Occurs in following conditions - malnutrition - starvation - fasting - hypoproteinaemia Amino acids released from broken plasma proteins distributed throughout body to form cellular protein molecules Used as a last source of energy

5. 3. PLASMA PROTEINS FOR FLUID EXCHANGE Exert colloid osmotic pressure Play an important role in distribution of water between blood and tissues AT ARTERIAL END OF CAPILLARIES : Hydrostatic pressure > osmotic pressure. Hence, fluid driven out of vessels into tissue spaces. Plasma proteins, however, do not leave capillaries because of their large size. AT VENOUS END OF CAPILLARIES : Osmotic pressure > hydrostatic pressure because of presence of plasma proteins in capillaries. Hence, fluid is drawn from tissue spaces into vessels. This allows exchange of fluids and dissolved materials between blood and tissue spaces (STARLING HYPOTHESIS)

6. 4. PLASMA PROTEINS AS BUFFERS Amphoteric molecules In acidic pH . Amino group of plasma proteins combine with a proton and becomes positively charged In alkaline medium , carboxyl group of plasma proteins donate a proton and becomes negatively charged In this way, plasma proteins maintain a constant pH of the medium.

7. 5. TRANSPORT FUNCTION OF PLASMA PROTEINS Binds to and transport various substances throughout body Eg. 1) Albumin transport ions, drugs, penicillin, gases, pigments, ect 2) lipoproteins transport lipid fractions and fat-soluble vitamins 3) haptoglobin transport free haemoglobin 4) transferrin transport iron

8. 7. ROLE OF PLASMA PROTEINS IN VISCOSITY OF BLOOD Makes blood viscous Albumin, globulins and fibrinogen mainly responsible Due to the large size and asymmetrical structure of plasma proteins Viscosity provides resistance to blood flow in vessels This maintains blood pressure in normal range

9. 8. PLASMA PROTEINS FOR BODY DEFENCE Gamma-globulins also known as immunoglobulin Act as antibodies against antigens to protect body against infections like diphtheria, thyroid, streptococcal infections, mumps, influenza, measles, hepatitis, rubella, poliomyelitis, ect.

10. 9. PLASMA PROTEINS AS ENZYMES Enzymes are proteins (except ribozymes ) Eg . 1) Amylase 2) transaminase 3) dehydrogenase 4) lipase 5) phosphatase

11. 10. PLASMA PROTEINS AS HORMONES Certain hormones are proteins Eg . 1) Oxytocin 2) Vasopressin 3) insulin 4) Parathormone 5) TSH 6) ACTH

12. 11. ROLE OF PLASMA PROTEINS IN BLOOD COAGULATION Plasma contains fibrinogen, enzymes and clotting factors These participate in coagulation of blood Prevent excessive loss of blood during injury

13. CLINICAL SIGNIFICANCE OF PLASMA PROTEINS

14. Normal plasma protein level = 6-8 g% Increase in plasma protein levels Decrease in Plasma protein levels HYPERPROTEINAEMIA HYPOPROTEINAEMIA

15. HYPERPROTEINAEMIA Increase in total amount of plasma proteins in the body Occurs in following 2 situations: 1) Haemoconcentration - due to dehydration - both albumin and globulin are increased - A:G ratio remains unchanged 2) Diseases such as hypergammaglobulinaemia - high levels of plasma globulins - albumin level normal or reduced - A:G ratio reversed if albumin reduced

16. HYPERGAMMAGLOBULINAEMIA POLYCLONAL GAMMOPATHIES MONOCLONAL GAMMOPATHIES

17. Chronic infections like TB, leprosy, kalaazar, etc Chronic liver disease like cirrhosis or chronic active hepatitis Sarcoidosis Autoimmune diseases like rheumatoid arthritis POLYCLONAL GAMOPATHIES

18. MONOCLONAL GAMMOPATHIES MALIGNANT BENIGN Multiple myeloma Macroglobulinaemia Lymphoreticular malignancies like lymphosarcoma, leukemia, hodgkin’s disease Secondary to diabetes mellitus, Chronic infections, etc Idiopathic

19. HYPOPROTEINAEMIA Haemodilution Hypoalbuminaemia Hypogammaglobulinaemia

20. HAEMODILUTION Cause may be Water intoxication Both albumin and globulin are decreased A:G ratio remains unaltered Results in edema because of low plasma proteins in capillaries to exert colloid osmotic pressure

21. HYPOALBUMINAEMIA LOSS OF ALBUMIN FROM THE BODY - RENAL : Nephrotic syndrome - GIT : Protein losing enteropathy - SKIN : Burns and other skin lesions DECREASED SYNTHESIS OF ALBUMIN - SEVERE LIVER DISEASES : cirrhosis of liver , chronic hepatitis - NON-AVAILABILITY OF PRECURSORS : Malabsorption syndrome, protein calorie malnutrition - GENETIC DEFICIENCIES : Analbuminaemia MISCELLANEOUS - Acute or chronic illnesses - infections - malignancy - pregnancy

22. HYPOGAMMAGLOBULINAEMIA LOSS OF GAMMA-GLOBULINS FROM BODY - RENAL : Nephrotic syndrome - GIT : Protein losing enteropathy - SKIN : Burns and other skin lesions DECREASED SYNTHESIS OF GAMMA-GLOBULINS - TRANSIENT : Neonates/infants - PRIMARY : Genetic deficiency - SECONDARY : AIDS, LEUKEMIA 3) MISCELLANEOUS - Pregnancies

23. ALBUMIN

24. Structure of Albumin. Most abundant and fairly homogeneous protein of plasma. Half of the total plasma protein is made up of albumin.

25. Plasma protein composition

26. Single polypeptide chain. Contain 585 amino acids. Have 17 interchain disulfide (s-s) bonds. Molecular weight : 69 000 Low isoelectric pH ( pI = 4.7) Precipitates last in salting out or alcohol precipitation method. Normal value: 3.5 – 5.5 mg/ dL

27. Normal pattern of serum proteins on electrophoresis Normal values % of total proteins Albumin 50 - 70 α globulin 7 - 17 β gobulin 7 - 16 γ globulin 11 - 22

28. Synthesis of albumin Exclusively synthesised by the liver. Liver produces approximately 12g albumin per day which represents 25% of the total hepatic protein synthesis. Albumin has a half life of 20 days.

29. Albumin 67 % α helix 10 % β turn

30. Amino acid composition Amino Acid Composition Aspartic Acid 36 Asparagine 17 Threonine 28 Serine 24 Glutamic Acid 62 Glutamine 20 Proline 24 Glysine 12 Alanine 62

31. Valine 41 Cystine 35 Methionine 6 Isoleucine 8 Leucine 61 Tyrosine 18 Phenyalanine 31 Lysine 59 Histidine 16 Tryptophan 1 Arginine 24 TOTAL 585

32. Functions of albumin: Osmotic Function Due to its high concentration and low molecular weight, albumin contributes to 75 – 80% of the total plasma osmotic pressure. Thus, albumin plays a predominant role in maintaining blood volume and body fluid distribution. Transport Function Plasma albumin binds to several biochemically important compounds and transports them in the circulation. These include free fatty acids which is transported to the liver, bilirubin, steroid hormones, calcium and copper. Nutritive Function Albumin serves as a source of amino acids for tissue protein synthesis to a limited extent, particularly in nutritional deprivation of amino acids.

33. Buffering Function Among the plasma proteins, albumin has the maximum buffering capacity. Exerts low viscocity Plays an important role in exchange of water between tissue fluid and blood. Certain drugs also bind to albumin. e.g sulphonamides, aspirin, penicillin. These drugs are directly transported to the target organ.

34. Clinical significance Hypoalbuminemia Hyperalbuminemia

35. Hypoalbuminemia Occurs due to a decrease in concentration of albumin, i.e when it is less than 2.5 gm% Causes (1) Loss from the body Loss of albumin in urine in nephrotic syndrome In burns, albumin is loss through the unprotected skin surface. (2) Decreased synthesis of albumin Severe liver diseases: chronic hepatitis, cirrhosis liver. Non-availability of the precursor: malabsorption syndrome, protein calorie malnutrition Genetic deficiency: Analbuminaemia (3) Others Chronic illness, infections, Malignancy, pregnancy

36. Decrease in albumin concentration leads to oedema formation. Oedema is a situation where tissue swelling takes place.

37. Treatment of oedema: increasing blood protein level in patient with a nutritional deficiency. Diuretic treatment – kidney is made to excrete excess fluid from the body.

38. hyperalbuminemia Occur when albumin level is high, i.e greater than 5.5 gm% Seen in the absence of dehydration. Frequent in obese men.

39. Thank you for your attention....