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Body fluid & cell membrane
Nermeen Bastawy
Physiology Department
Faculty of Medicine
Cairo University
75 % 60%
40 % 20%
ISF IVF
15% 5%
plasma
Differences between ICF & ECF
Cations mmol/lICFPlasma
Na+10145
K+1554.5
HCO3-1028
Osmolarity mOsm/l
300300
Ficks Principle
• Amount = vol. X conc.
• Vol. = A/C (in plasma)
Amount of dye
Conc.
Ficks Principle
• TBW heavy water or antipyrine
• ECF inulin or Na thiocyanate
• Plasma Evan blue or Iodine labelled-ptn
• ICF
• ISF
ISF Plasma
Homeostasis # Hemostasis
Keeping the conditions in the internal environment constant.
Stoppage of bleeding
CELL MEMBRANNEFlexibility & Selective permeabilityImmunity & cell adhesion
Structural ptn Identify ptn Enzymes Carriers (in facilitated diffusion & active trans.) Receptors & channels Connections (cell-cell or cell-basal lamina) Cytoskeleton fixation
Functions of cell membrane proteins
Receptors & channel
Types of channels
Non-gated channels Gated channels
ReceptorsReceptors
Down regulation
excess ligand --- no. & sensitivity of R.
Up-regulation
few ligand ++ no. & sensitivity of R.
Cells connections & CAMs
Connexon
TRANSPORT THROUGH THE CELL MEMBRANE
Substances can pass through a cell membrane in 3 separate ways:
(I) Diffusion (simple/ facilitated/osmosis).
(II) Active transport (1ry/2ry).
(III) Vesicular transport (end/exocytosis)
Simple Diffusion
Dye in water Diffusion Equilibrium
Distance XMW
Temp. XSA XGradient Conc. rateDiffusion
Diffusion
Cell membrane
Distance XMW
Temp. XSA XGradient Conc. rateDiffusion
Natural Kinetic E.
1. Through the lipid bilayera) The lipid soluble: gases
b) H2O: penetrates like bullets
c) Lipid insoluble (small & uncharged): urea.
2. Through protein channels
Mainly for hydrated ions They are distinguished by:
• Selective permeability
• Gating of protein channels
Simple diffusion pathways
Do you think you understand diffusion?
++
++
++
Facilitated Diffusion
- large polar molecules:glucose & aa.
- carrier ptn differ from channel:
Larger
Transport part-way not all mem.
Specific receptor (binding site)
Conformational change
Conformational changes of carrier ptn
Characters of Facilitated diffusion
• Specificity
• Saturation: maximum rate of diffusion.
• Sensitivity to temperature >simple diffusion
• Similar substances have competition
Osmosis and Osmotic Pressure
OP
• Mole: MW of substance in gram. • Osmole: No. of particles in 1 Mole• Osmolality: No. of osmoles dissolved in 1 kg water.• Osmolarity: No. of osmoles in 1 L water. • Tonicity : Osmolality of a solution relative to plasma:
- Isotonic = 300 mOsmol/l- Hypotonic < 300 mOsmol/l- Hypertonic >300 mOsmol/l
• 1 osmole /l = 19300 mmHg OP.• 1 mOsmol/l = 19.3 mmHg OP• The osmolarity of ICF = ECF = 300 mOsmol/l• 300 X 19.3 = 5000 mmHg OP
• To maitain homeostasis, cells must keep certain conc. for some molecules.
• Passive fiffusion cant do this
K+
Na+Ca++
Active Transport
Simple diffusion facilitated
Types of active transport
1ry 2ry
Do you think you understand active transport?
Na+
K+
E
1ry
Vesicular Transport
It is the movement of macromolecules.2 types: Endocytosis and Exocytosis.Endocytosis: It is the movement from outside the cell to the inside.Exocytsis: It is the movement from inside the cell to the outside.
Endocytosis
• Pinocytosis = cell drinking: It is the only mean by which some very large water soluble macromolecules such as proteins can enter the cells as small invaginating vesicles containing ECF.
• Phagocytosis = cell eating: it involves large particulate matter e.g. bacteria and dead tissue.
Do you think you understand vesicular transport?
Gibbs Donnan Equilibrium• When two solutions
containing ions are separated by membrane that is permeable to some of the ions and not to others an electrochemical equilibrium is established
• Electrical and chemical energies on either side of the membrane are equal and opposite to each other
Regulating systems
Nervous systemNervous system
rapid & short duration
Endocrine systemEndocrine system slow & long duration