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Scientific Method and Yeast Fermentation in General Biology lab 2

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Terms in this set (21)

  • What is the first step of the Scientific Method?
    Observation of an occurrence which leads to stating a problem or question to answer.
  • Define a hypothesis in the Scientific Method.
    A tentative, testable explanation based on current knowledge, formulated using inductive reasoning.
  • What is inductive reasoning?
    Reasoning from specific details to a general statement or conclusion.
  • What is deductive reasoning in the context of the Scientific Method?
    Starting with a general statement and inferring specific conclusions to design experiments.
  • What is the difference between independent and dependent variables?
    The independent variable is manipulated; the dependent variable is the expected result measured.
  • What is the purpose of controls in an experiment?
    To ensure validity by comparing samples that undergo all steps except the one being tested.
  • What distinguishes positive controls from negative controls?
    Positive controls contain a known sample that produces a reaction; negative controls do not change the reagent.
  • Can a hypothesis be proven true in science?
    No, it can only be supported or refuted by data; repeated support may lead to a scientific theory.
  • What is catabolism in yeast metabolism?
    A metabolic reaction breaking down macromolecules to release stored energy.
  • What are the two metabolic pathways yeast can use to break down sugars?
    Aerobic metabolism (with oxygen) and fermentation (anaerobic metabolism without oxygen).
  • Write the general equation for aerobic metabolism of sugar by yeast.
    Sugar + O2 → H2O + CO2 + released energy.
  • Write the general equation for fermentation by yeast.
    Sugar → Ethanol + CO2 + released energy.
  • Why does aerobic metabolism not change gas pressure in a sealed chamber?
    Because oxygen consumption equals carbon dioxide production, keeping gas pressure constant.
  • Why does fermentation increase gas pressure in a sealed chamber?
    Because CO2 is produced without oxygen consumption, increasing gas pressure.
  • Why is oil added on top of the yeast-sugar mixture in the experiment?
    To create an airtight seal preventing oxygen from entering, ensuring fermentation occurs.
  • What gas does the Vernier Gas Pressure Sensor measure in this experiment?
    Carbon dioxide (CO2) produced during fermentation.
  • What is the independent variable in the yeast fermentation experiment?
    The type of sugar solution used (e.g., glucose, sucrose, lactose).
  • What is the dependent variable in the yeast fermentation experiment?
    The fermentation rate measured as the slope of gas pressure increase (kPa/sec).
  • Why is yeast incubated for 10 minutes before data collection?
    To allow yeast to begin fermentation and stabilize gas production for accurate measurement.
  • Why is water used as one experimental treatment in the yeast fermentation experiment?
    As a negative control to show no fermentation occurs without sugar.
  • List five conditions kept constant across all experimental treatments.
    Temperature, yeast concentration, incubation time, volume of solutions, and airtight sealing.