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