PLASMA AND PLASMA PROTEINS
PLASMA
Plasma is the clear, straw-coloured fluid (with dissolved solid substances) portion of the
blood minus its cellular elements. It constitutes about 55% of the blood volume.
COMPOSITION
Plasma contains the following constituents:
Water
Water is the main constituent of plasma forming 91% of it.
Solids.
9% of the plasma.
The solid constituents of plasma are given below:
Plasma proteins
7% of the solids in plasma. Their normal value ranges from 6.4 to 8.3 g/dL.
They include albumin, globulins, fibrinogen and others.
Other organic molecules which form 1% of the solids include the following:
Carbohydrates, mainly glucose (100–120 mg/dL).
Fats are neutral fats (30–150 mg/dL),
phospholipids (150–300 mg/dL)
cholesterol (150–240 mg/dL).
Non-protein nitrogenous (NPN) substances (28–40 mg/dL)
ammonia (traces), amino acids, creatine (1–2 mg/dL), creatinine (0.6–1.2 mg/dL),
xanthine (traces), hypoxanthine (traces), urea (20–40 mg/dL) and uric acid (2–4 mg/dL).
Hormones
Enzymes
antibodies.
Inorganic substances
which constitute 1% of the solids in plasma
include sodium, potassium, calcium, magnesium, chloride, iodide, iron, phosphates
and copper.
Gases
, oxygen, carbon dioxide and nitrogen.
Serum
Plasma from which fibrinogen and clotting factors (II, V and VIII) have been removed is
called serum.
Serum is formed when the blood is allowed to clot in a test tube and the clot is
retracted.
Serum has a higher serotonin (5HT) content because of the breakdown of platelets
during clotting.
PLASMA PROTEINS
Albumin (4.8 g/dL)
Globulins (2.3 g/dL)
o Alpha 1 (α1) globulin
o Alpha 2 (α2) globulin
o Beta (β) globulin
o Gamma (γ) globulin
Fibrinogen (0.3 g/dL)
PROPERTIES OF PLASMA PROTEINS
1. Molecular weight.
Plasma proteins are large molecules with the following molecular weight: Albumin:
69,000, Globulins: 90,000–1,56,000 and Fibrinogen: 5,00,000. Thus the fibrinogen
has got highest molecular weight.
2. Osmotic pressure.
The plasma proteins exert an osmotic pressure of about 25 mm Hg.
3. Specific gravity.
The specific gravity of plasma proteins is 1.026.
4. Isoelectric point.
Proteins can ionize either as acids or as bases owing to the fact that the side chains of
their constituent amino acids contain a selection of amino group (NH2) and carboxyl
groups (–COOH).
At an intermediate pH (specific for each protein) the protein molecules carry equal
number of positive and negative charges and hence have a zero net charge. This pH
value for electrical neutrality of the molecule is known as the isoelectric point.
5. Electrophoretic mobility.
PLASMA
Plasma is the clear, straw-coloured fluid (with dissolved solid substances) portion of the
blood minus its cellular elements. It constitutes about 55% of the blood volume.
COMPOSITION
Plasma contains the following constituents:
Water
Water is the main constituent of plasma forming 91% of it.
Solids.
9% of the plasma.
The solid constituents of plasma are given below:
Plasma proteins
7% of the solids in plasma. Their normal value ranges from 6.4 to 8.3 g/dL.
They include albumin, globulins, fibrinogen and others.
Other organic molecules which form 1% of the solids include the following:
Carbohydrates, mainly glucose (100–120 mg/dL).
Fats are neutral fats (30–150 mg/dL),
phospholipids (150–300 mg/dL)
cholesterol (150–240 mg/dL).
Non-protein nitrogenous (NPN) substances (28–40 mg/dL)
ammonia (traces), amino acids, creatine (1–2 mg/dL), creatinine (0.6–1.2 mg/dL),
xanthine (traces), hypoxanthine (traces), urea (20–40 mg/dL) and uric acid (2–4 mg/dL).
Hormones
Enzymes
antibodies.
Inorganic substances
which constitute 1% of the solids in plasma
include sodium, potassium, calcium, magnesium, chloride, iodide, iron, phosphates
and copper.
Gases
, oxygen, carbon dioxide and nitrogen.
Serum
Plasma from which fibrinogen and clotting factors (II, V and VIII) have been removed is
called serum.
Serum is formed when the blood is allowed to clot in a test tube and the clot is
retracted.
Serum has a higher serotonin (5HT) content because of the breakdown of platelets
during clotting.
PLASMA PROTEINS
Albumin (4.8 g/dL)
Globulins (2.3 g/dL)
o Alpha 1 (α1) globulin
o Alpha 2 (α2) globulin
o Beta (β) globulin
o Gamma (γ) globulin
Fibrinogen (0.3 g/dL)
PROPERTIES OF PLASMA PROTEINS
1. Molecular weight.
Plasma proteins are large molecules with the following molecular weight: Albumin:
69,000, Globulins: 90,000–1,56,000 and Fibrinogen: 5,00,000. Thus the fibrinogen
has got highest molecular weight.
2. Osmotic pressure.
The plasma proteins exert an osmotic pressure of about 25 mm Hg.
3. Specific gravity.
The specific gravity of plasma proteins is 1.026.
4. Isoelectric point.
Proteins can ionize either as acids or as bases owing to the fact that the side chains of
their constituent amino acids contain a selection of amino group (NH2) and carboxyl
groups (–COOH).
At an intermediate pH (specific for each protein) the protein molecules carry equal
number of positive and negative charges and hence have a zero net charge. This pH
value for electrical neutrality of the molecule is known as the isoelectric point.
5. Electrophoretic mobility.
