Plasma protein

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

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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

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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 gt 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 gt
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)

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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.

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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

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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

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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.

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9. PLASMA PROTEINS AS ENZYMES

• Enzymes are proteins (except ribozymes)
• Eg. 1) Amylase
• 2) transaminase
• 3) dehydrogenase
• 4) lipase
• 5) phosphatase

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10. PLASMA PROTEINS AS HORMONES

• Certain hormones are proteins
• Eg. 1) Oxytocin
• 2) Vasopressin
• 3) insulin
• 4) Parathormone
• 5) TSH
• 6) ACTH

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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

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CLINICAL SIGNIFICANCE OF PLASMA PROTEINS
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HYPERPROTEINAEMIA
Increase in plasma protein levels
Normal plasma protein level 6-8 g
Decrease in Plasma protein levels
HYPOPROTEINAEMIA
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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
• - AG ratio remains unchanged
• 2) Diseases such as hypergammaglobulinaemia
• - high levels of plasma globulins
• - albumin level normal or reduced
• - AG ratio reversed if albumin reduced

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HYPERGAMMAGLOBULINAEMIA
MONOCLONAL GAMMOPATHIES
POLYCLONAL GAMMOPATHIES
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POLYCLONAL GAMOPATHIES

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

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MONOCLONAL GAMMOPATHIES
BENIGN
MALIGNANT

• Secondary to diabetes mellitus, Chronic
  infections, etc
• Idiopathic

• Multiple myeloma
• Macroglobulinaemia
• Lymphoreticular malignancies
• like lymphosarcoma, leukemia,
• hodgkins disease

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HYPOPROTEINAEMIA
Hypogammaglobulinaemia
Haemodilution
Hypoalbuminaemia
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HAEMODILUTION

• Cause may be Water intoxication
• Both albumin and globulin are decreased
• AG ratio remains unaltered
• Results in edema because of low plasma proteins
  in
• capillaries to exert colloid osmotic pressure

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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

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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

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ALBUMIN
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Structure of Albumin.

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

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Plasma protein composition
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• 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

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Normal pattern of serum proteins on
electrophoresis

• Normal values of total proteins
• Albumin 50 - 70
• a globulin 7 - 17
• ß gobulin 7 - 16
• ? globulin 11 - 22

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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.

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

585
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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.

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• 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.

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• 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.

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• 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.

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• Certain drugs also bind to albumin.
• e.g sulphonamides, aspirin, penicillin.
• These drugs are directly transported to the
  target organ.

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Clinical significance

• Hypoalbuminemia
• Hyperalbuminemia

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Hypoalbuminemia

• Occurs due to a decrease in concentration of
  albumin, i.e when it is less than 2.5 gm

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Causes

• (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

• Loss from the body
• Loss of albumin in urine in nephrotic syndrome
• In burns, albumin is loss through the unprotected
  skin surface.

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

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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.

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hyperalbuminemia

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

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Summary

• Classification of plasma protein.
• Functions of plama protein.
• Albumin.
• Clinical significance.

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Bibliography

• Wikipedia
• Textbook of medical physiology MN Chatterjea,
  Rana Shinde
• google images

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