# Chemical and Physical Foundations of Biological Systems Section: Content Category 4B

Importance of fluids for the circulation of blood, gas movement, and gas exchange
Fluids are featured in several physiologically important processes, including the circulation of blood, gas movement into and out of the lungs, and gas exchange with the blood. The energetic requirements of fluid dynamics can be modeled using physical equations. A thorough understanding of fluids is necessary to understand the origins of numerous forms of disease.

The content in this category covers hydrostatic pressure, fluid flow rates, viscosity, the Kinetic Molecular Theory of Gases, and the Ideal Gas Law. The topics and subtopics are below.

### Topic Level Key:

The abbreviations found in parentheses indicate the course(s) in which undergraduate students at many colleges and universities learn about the topics and associated subtopics. The course abbreviations are:
BIO = two-semester sequence of introductory biology
GC = two-semester sequence of general chemistry
PHY = two-semester sequence of introductory physics

Please note topics that appear on multiple content lists will be treated differently. Questions will focus on the topics as they are described in the narrative for the content category.

### Fluids (PHY)

• Density, specific gravity
• Buoyancy, Archimedes’ Principle
• Hydrostatic pressure
• Pascal’s Law
• Hydrostatic pressure; P = ρgh (pressure vs. depth)
• Viscosity: Poiseuille Flow
• Continuity equation (A⋅v = constant)
• Concept of turbulence at high velocities
• Surface tension
• Bernoulli’s equation
• Venturi effect, pitot tube

### Circulatory System (BIO)

• Arterial and venous systems; pressure and flow characteristics

### Gas Phase (GC, PHY)

• Absolute temperature, (K) Kelvin Scale
• Pressure, simple mercury barometer
• Molar volume at 0°C and 1 atm = 22.4 L/mol
• Ideal gas
• Definition
• Ideal Gas Law: PV = nRT
• Boyle’s Law: PV = constant
• Charles’ Law: V/T = constant
• Avogadro’s Law: V/n = constant
• Kinetic Molecular Theory of Gases
• Heat capacity at constant volume and at constant pressure (PHY)
• Boltzmann’s Constant (PHY)
• Deviation of real gas behavior from Ideal Gas Law
• Qualitative
• Quantitative (Van der Waals’ Equation)
• Partial pressure, mole fraction
• Dalton’s Law relating partial pressure to composition

### Example Question Video

To support your studies, see the following video tutorials below from the Khan Academy MCAT Collection. The videos and associated questions were created by the Khan Academy in collaboration with the AAMC and the Robert Wood Johnson Foundation.