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