MCAT Chem/Phys — Medium Core Concepts

Front

Bernoulli's Principle: Equation & Biological Application

Back

Equation: P + 1/2 rho v^2 + rho g h = constant. It states that for an incompressible, non-viscous fluid, an increase in flow velocity (v) leads to a decrease in pressure (P). **Clinical App:** In the circulatory system, vasoconstriction increases velocity, causing a pressure drop that helps draw blood into narrower vessels.

Front

Resistivity vs. Resistance (Circuit Elements)

Back

**Resistance (R):** Depends on geometry and material. Formula: R = rho (L / A), where rho is resistivity, L is length, and A is cross-sectional area. **Resistivity (rho):** An intrinsic property of the material independent of shape. **MCAT Trap:** Doubling the length of a wire doubles resistance, but doubling the cross-sectional area halves resistance.

Front

Enzyme Kinetics: Michaelis Constant (Km)

Back

Km is the substrate concentration at which the reaction rate (V) is half of the maximum velocity (Vmax). It indicates the enzyme's affinity for its substrate: **Low Km = High Affinity** (saturates quickly), **High Km = Low Affinity** (requires more substrate). This is derived from the Michaelis-Menten equation: V = (Vmax [S]) / (Km + [S]).

Front

Doppler Effect: Frequency Shift Equation

Back

Equation: f_obs = f_src * ((v + v_r) / (v + v_s)). **Sign Convention:** If the source and receiver are moving closer, perceived frequency increases (blue shift). If moving apart, frequency decreases (red shift). **MCAT App:** Used in echocardiography to measure blood flow velocity and direction.

Front

Thermodynamics: Gibbs Free Energy (Delta G)

Back

Formula: Delta G = Delta H - T(Delta S). Determines spontaneity at constant temperature and pressure. If Delta G < 0, the process is spontaneous. **Relationship to Keq:** Delta G = -RT ln(K_eq). A negative Delta G correlates with K_eq > 1, favoring products.