Q1iii: Role of Plasma Proteins

Plasma Proteins

Type

Albumin

Amt (g/L)

45

Role

Oncotic pressure

Acid – Base (15% buffering of carbamino compounds)

Transport – bilirubin, Ca2+, hormones, FFA, drugs

Metabolism – broken down to amino acids for catabolism

Type

Globulins

α1

Amt (g/L)

25

Role

α-1 antitrypsin – protease inhibitor, inhibits trypsin, chymotrypsin, plasma

Lipoproteins – chylomicrons, VLDL, LDL, HDL → transport lipids

α1 acid glycoprotein – binding basic drugs, acute phase reactant

Type

α2

Amt (g/L)

25

Role

α2 macroglobulin – protease inhibitor

Prothrombin – coagulation

Haptoglobin – scavenges free Hb (intravascular haemolysis)

Caeruloplasmin – binds copper, acute phase reactant

Type

β

Amt (g/L)

25

Role

Transferrin – binds 2Fe3+

Type

γ

Amt (g/L)

25

Role

Immunoglobulins → from B lymphocytes

IgG

76%

Binds complement

IgA

16%

Present in seromucous secretions

IgM

7%

Fixes complement

IgE

1%

Binds MCs in hypersensitivity

Type

Fibrinogen

Amt (g/L)

3

Role

Final step of coagulation → fibrin clot

Type

Cytokine

Amt (g/L)

Role

IL, IFN, chemokines, lymphokines, TNF → mediate immune response

Type

Complement

Amt (g/L)

Role

25 proteins produced by liver/RES → innate immunity amplification

Type

CRP

Amt (g/L)

Role

Inflammatory mediator

Type

Coagulation

Amt (g/L)

Role

Trigger coagulation cascade – biological amplification system

Functions

Proteolytic Systems

  • Complement
  • Coagulation
  • Fibrinolytic
  • Kinin systems

Role in Acid/Base

  • Buffers (can dissociate to accept H+)
  • CO2 transport

Oncotic Pressure

  • NFP = k[(Pc – Pi) – σ (πc – πi)]
  • Capillaries are impermeable to plasma proteins
  • ∴exert oncotic P ~25mmHg, holds fluid intravascularly

Transport

  • Hormones (T3/T4)
  • Drugs
  • Metal cations
  • Bilirubin
  • FFA

Enzyme Activity

  • Pseudocholinesterase

Immune Response

  • Ab production
  • Cytokines

Metabolic

  • Protein broken down → amino acid → E