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The Plasma Membrane – a Phospholipid Bilayer
Components of Plasma Membrane
Lipids Proteins
1) Phospholipids
2) Cholesterol
3) Glycolipds
1) Peripheral (Associated)
2) Integral (Membrane Spanning)
3) Glycoproteins
~50% ~50%
(75%)
(20%)
(5%)
Roles of the Plasma Membrane
Protein Transporters
1) Channels 2) Carriers
a) open
b) gated** triggered to open
Cell Transport Mechanisms
Passive Active
1) Diffusion
2) Facilitated Diffusion
3) Filtration
1) Primary (Direct)
2) Secondary (Indirect)
3) Vesicular
Diffusion
Rate of Diffusion
Primary Active Transport: The Na+/K+ Pump
Antiport
The Na+/K+ Pump
Secondary Active (Indirect):
e.g.,
Na+/Glucose transporter
Symport
The Na+/glucose Symport
Transportation of the usual suspects
Endocytosis and Exocytosis
Transcytosis – e.g., inside Vesicle.
Tissue Compartment Volumes
• 67% is intracellular
• About 60-70% of body weight is water
• 33% is extracellular– 8% plasma– 25% interstitial
Distribution of Water and Solutes in the Body Compartments
Inside cells
Transcapillary Fluid Dynamics
HP = Hydrostatic Pressure (force of a fluid on walls of its container)
↑HP ↓HP
↑↑ COP
↓↓ COP
↑↑ COP
COP = Colloid Osmotic Pressure (force generated by proteins in solution)
↓HP
Cells (ICF)
(interstitium)
arterialend
venousend
(plasma in capillary)
Filtration Reabsorption
= fluid movement