Yeast Fermentation and the Effect of Temperature on Metabolic Rate
Science Lab · Grade 7
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Type
science_lab
Pre Lab
Background: Have you ever watched bread dough rise or seen bubbles form in a glass of apple cider? Those bubbles are produced by tiny living organisms called yeast. Yeast are single-celled fungi that survive by breaking down sugars for energy — a process called **fermentation**. During fermentation, yeast convert glucose (a simple sugar) into ethanol and **CO2 production** (carbon dioxide gas). This CO2 is what makes bread dough puff up and causes bubbles in fermented drinks. Fermentation is one example of **metabolism** — all the chemical reactions happening inside a living organism to keep it alive and functioning.
The speed at which an organism carries out its metabolic reactions is called its **metabolic rate**. Like most chemical reactions, metabolism is affected by temperature. When temperatures are warmer, molecules move faster and collide more often, which can speed up chemical reactions. When temperatures are too cold, molecular movement slows down and reactions happen less frequently. However, if temperatures get too hot, the proteins (enzymes) that run these reactions can be damaged and stop working altogether. This means every living organism has a temperature range where its metabolism works best.
In today's lab, you will act as scientists to **plan an investigation** that tests how temperature affects yeast fermentation. By measuring the amount of CO2 gas produced by yeast at different temperatures, you can compare their **metabolic rate** across conditions. You will identify your **independent variable** (the factor you change — temperature), your **dependent variable** (the factor you measure — CO2 production), and your **controlled variables** (all the factors you keep the same). Then you will **analyze your data** to look for patterns and **construct an explanation** supported by evidence.
Vocabulary
Term: metabolism
Definition: All of the chemical reactions that occur inside a living organism to maintain life, including breaking down food for energy and building new molecules.
Term: metabolic rate
Lab Type
Post Lab
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Teacher Notes
Estimated Time
Experiment Design
Research Question
Learning Objectives
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