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Questions and Answers
Which plasma proteins are primarily responsible for blood clotting?
What is the role of γ-globulins in the body?
What contributes to maintaining the pH of blood at a constant level?
How do plasma proteins affect capillary function?
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Which of the following statements about plasma viscosity is true?
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What percentage of blood does plasma constitute?
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Which of the following plasma proteins has the highest concentration in blood?
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Which inorganic constituent is considered the chief inorganic cation in plasma?
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What is the primary function of plasma proteins related to osmotic pressure?
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Where are most globulins synthesized?
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Study Notes
Blood Composition
- Blood is a vital component of the extracellular fluid, circulating throughout the body via the cardiovascular system.
- It accounts for 8% of body weight, approximately 5.6 liters in a typical adult male.
Blood Components
- Blood consists of two primary components: plasma (55%) and the cellular part (45%).
- Plasma is the fluid portion of blood, while the cellular part comprises red blood cells, white blood cells, and platelets.
Plasma: The Fluid Component
- Plasma is a clear, yellowish fluid, making up about 3.5 liters (5% of body weight).
- Plasma clots when allowed to stand, leaving behind a remnant called serum.
Plasma Composition
- Water (90%): The primary constituent of plasma.
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Organic Substances (9.1%):
- Plasma proteins (7.2-7.4 g/dl) play crucial roles in various physiological functions.
- Lipids, glucose, amino acids, vitamins, enzymes, and waste products are also present.
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Inorganic Constituents (0.9%):
- Sodium (Na+) is the main inorganic cation.
- Chloride (Cl-) is the primary inorganic anion.
- Bicarbonate (HCO3-), phosphates, and sulfates are also present.
- Blood Gases (O2, CO2, N2): Essential for gas exchange and respiration.
Plasma Proteins: Key Players in Blood Physiology
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Types: Several plasma proteins exist, with albumin, globulin, fibrinogen, and prothrombin being the most significant.
- Albumin: 3.5-5 g/dl, molecular weight 69,000.
- Globulin: 2.5 g/dl, molecular weight 90,000-156,000.
- Fibrinogen: 0.4 g/dl, molecular weight 340,000.
- Prothrombin: 0.01 g/dl, molecular weight 68,700.
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Sites of Formation:
- Albumin, fibrinogen, and prothrombin are synthesized in the liver.
- Globulins are produced both in the liver (50%) and in plasma cells of the reticuloendothelial system (50%), a network of cells found primarily in the liver, spleen, lymph nodes, and bone marrow.
Functions of Plasma Proteins: A Multifaceted Role
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Osmotic Function:
- Plasma proteins contribute to the total osmotic pressure of plasma (25 mmHg), also known as colloidal osmotic pressure or oncotic pressure.
- This pressure aids in regulating the exchange of fluids between interstitial fluid and blood through capillary membranes, influencing blood volume.
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Transport Function:
- Albumin and globulins (α and β) act as carriers for vital substances like hormones, vitamins, lipids, and minerals.
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Defensive Function:
- γ-globulins, also termed immunoglobulins or antibodies, play a critical role in defending the body against microorganisms and their toxins.
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Blood Clotting Function:
- Prothrombin and fibrinogen are essential for the process of blood clotting.
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Viscosity:
- Plasma proteins contribute to the viscosity of blood, making it 3-5 times as viscous as water. Plasma alone is 1.5 times as viscous as water.
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Capillary Function:
- Plasma proteins influence capillary permeability by partially blocking pores in the capillary membrane.
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Buffer Function:
- Plasma proteins act as weak acids or bases, maintaining the pH of blood at a stable 7.4.
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Source of Tissue Proteins:
- Plasma proteins can be broken down into amino acids in the liver and macrophages, providing a source of rapid protein replacement for depleted tissues.
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Description
This quiz explores the composition of blood, highlighting its vital components such as plasma and cellular elements. Learn about the percentages of plasma, its constituents, and the role of blood in the body. Ideal for students studying biology or health sciences.