Composition of blood

• Main components of blood

  • Plasma
  • Haematocrit, packed cell volume (PCV)
  • White blood cells
  • Platelets, Buffy coat
  • Erythrocytes (red blood cells)
• Function of blood


  1. Delivery: nutrients to tissue

  2. Waste collection: removes waste products

  3. Communication route: e.g. hormones from manufacturing site to target tissues

  4. Defence: External insult, Wound healing, Tissue repair
• Composition of whole blood

  • Cell free (55% of blood volume)
  • Make up about 45% of blood volume
  • 1% of blood volume
• Plasma constituents


  • Proteins (6-8% of plasma)
  • Anions (Cl-, HCO3-, PO43-) and Cations (Na+, K+, Ca2+, Mg2+)
  • Small molecules: e.g. glucose, amino acids (Gln, Ala), lactate, glycerol, urea, ketones
• Serum is the liquid component of blood when blood is allowed to clot; plasma contains clotting factors, serum does not
• Function of plasma proteins


  • Transport
  • Inflammatory response and immunity
  • Oncotic pressure
  • Haemostasis
• Albumin


  • Most abundant protein in plasma and is synthesized by liver
  • Negatively charged at physiological pH, highly polar, large capacity to non-specifically bind ligands -> fatty acid, steroid hormone, drugs
  • Transport protein
• Low Levels of Albumin -> Condition: Hypoalbuminaemia reduces the oncotic pressure and leads to oedema
• Other proteins involved in transport

  • Iron - Transferrin
  • Copper - Caeruloplasmin
  • Hormones - Thyroid hormone binding globulin, Cortisol binding globulin, Sex hormone binding globulin
  • Haemoglobin - Haptoglobulin
  • Lipids - Apolipoproteins
• What determines the concentration of proteins in the plasma?

  
  

  Blood volume -> Hydration,

  Rate of synthesis -> Liver, Cells of the immune system

  Rate of breakdown -> uptake and degradation of protein by cells

  Rate of loss-> via kidney and/or gut

• What measurements can be made using plasma proteins?

  
  

  serum electrophoretic pattern/serum protein electrophoresis -> allows separation and semi-quantitative assessment of individual proteins

  
  

  enzyme measurements -> detects cell damage

  
  

  total protein concentration -> limited clinical use
• Proteins in the plasma

  • albumin
  • α2
  • α1
  • b1
  • b2
  • g
  • transferrin
  • complement C3*
  • α1-antitrypsin
  • α1-acid glycoprotein*
  • Haptoglobulin*
  • α2-macroglobulin*
  • caeruloplasmin
  • IgG
  • IgA
  • IgM
  • IgD
  • IgE
• Albumin decreases in prolonged malnutrition, chronic liver or renal disease; increases in dehydration (fast, short term change)
• Increased alpha-globulins are indicative of acute inflammatory diseases
• Increased beta-globulins are indicative of liver disease
• Increased gamma-globulins indicate an overall increase in the broad y band, which can be indicative of chronic infection
• Decreased gamma-globulins indicate immune suppression or immune deficiency conditions
• Increased gamma-globulins in a sharp, distinct area of the y band can indicate multiple myeloma
• Changes in band density can be 'missed'; it takes a 30% change in albumin levels to show on the SPE
• Serum enzymes in diagnosis
• Enzymes and what they are indicative of

  • ALT (alanine aminotransferase): Liver damage
  • ALP (alkaline phosphatase): Bone deposition, liver damage, hyperthyroidism, biliary disease, increased steroid levels
  • GDH (glutamate dehydrogenase): Liver disease
  • y GT (g glutamyl transferase): Liver disease
  • CK (creatine kinase): Muscle damage
  • AST (aspartate aminotransferase): Muscle and liver damage
• Causes of hypoalbuminaemia :

  chronic liver disease, malnutrition, chronic renal disease
• Serum protein electrophoresis

  • not expensive
  • easy to perform screening procedure
  • agarose gel electrophoresis separates proteins on the basis of charge +
  • constant experimental condition -> highly reproducible pattern
• Limitations of serum protein electrophoresis

  • important proteins produced in low quantities -> low to detect
  • changes in band density can be missed, 30% change in albumin levels to show on SPE
  • age, life cycle, hormone changes
• enzyme activity in serum may be increased by cell proliferation or damage e.g cancer, cell death, trauma