introduction to body fluid & cell membrane

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