Bio 3 lab

Spectrophotometer

A device that shines light through a sample to measure how much light is absorbed (absorbance) or passes through (transmittance).

Absorbance vs Transmittance

They are inversely related — as absorbance increases, transmittance decreases, and vice versa.

Spectrophotometry Graph Interpretation

X-axis = wavelength, Y-axis = absorbance; the highest point (peak) shows the wavelength of maximum absorbance (λmax). High absorbance = strong light absorption.

Standard Curve and Concentration

Use the standard curve (absorbance vs concentration). Plug the absorbance into the equation y = mx + b to solve for concentration.

Peroxidase Reaction

Peroxidase uses hydrogen peroxide (H₂O₂) to oxidize guaiacol, forming a brown color. The spectrophotometer measures the color increase (absorbance) to show reaction rate.

Enzyme Activity: Temperature

Reaction rate increases with temperature until reaching an optimum, then decreases when enzyme denatures.

Enzyme Activity: pH

Each enzyme has an optimum pH where activity is highest; too acidic or basic reduces enzyme activity.

Enzyme Concentration Effect

More enzyme = faster reaction, until substrate runs out (rate levels off).

Competitive Inhibitor Effect

Binds to active site, slowing the reaction. More inhibitor = lower rate. Adding more substrate can overcome inhibition.

Cellular Respiration Equation

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy (ATP).

Cellular Respiration Measurement

Measure CO₂ output — more CO₂ means higher respiration rate and energy production.

Ethanol Fermentation Equation

C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂ + energy.

Ethanol Fermentation Measurement

Pressure increase from CO₂ shows fermentation rate — more pressure = more fermentation.

Calorimetry Definition

Burn food to heat water and measure energy content from temperature change.

Energy Gained by Water Equation

q = m × c × ΔT (mass of water × specific heat × temperature change).

Energy Content of Food Equation

Energy = q ÷ mass of food burned.