Fermentation (Karla Aviles)

Title: Fermentation

Principle(s) Investigated:

• Metabolic processes – conversion of sugar into energy
• Microbiology

Standards: Past in the appropriate NGSS standards.

MS-LS2-2

HS-LS1-7

HS-LS2-3

HS-LS2-4

Materials: Include a list of materials and sources from which they may be obtained.

• 1 package of active dry yeast or instant yeast
• Granulated sugar
• Water
• Electric Kettle
• 2-3 empty bottles
• Balloons
• At least one microscope – can substitute with images from Google (link to used images in the Procedure)

Procedure: Give a detailed explanation of the procedure and include diagrams if possible.

• Add two tablespoons (or 10 g) of yeast to a clean empty bottle
• Add two tablespoons (or 10 g) of granulated sugar to the bag.
• Add 1/3 cup (80ml) warm water to the bottle,
• Mix well and seal bottle with a balloon
• Place in warm area, or place bottle in warm water

Student prior knowledge: What prior concepts do students need to understand this activity?

• Basic understanding of prokaryotes and eukaryotes.
• Eukaryotic organelles involved in energy production, growth and reproduction
• Basic knowledge of chemical reactions (reactants → products) and the role of enzymes in chemical reactions

Explanation: Give a thorough explanation of the experiment or demonstration. Your explanation should be written to give your fellow teachers a solid understanding and include greater detail than what you might provide for your secondary students. Make certain to include equations whenever pertinent.

Aerobic respiration of yeast:

Enzymes

C6H12O6 + 6 O2 (g) → 6 H2O + 6 CO2 + energy

glucose oxygen water carbon dioxide

Anaerobic fermentation of glucose:

Enzymes

C6H12O6 → 2 CH3CH2OH + 2 CO2 + energy

glucose ethanol carbon dioxide

Living organisms such as protists, fungi, plants, and animals use aerobic respiration and/or fermentation (anaerobic respiration) to produce ATP for energy. Yeast can metabolize sugar aerobically, with the aid of oxygen, or anaerobically, without oxygen. Fermentation and aerobic respiration are multi-step processes that break the chemical bonds in glucose molecules to increase the production of adenosine triphosphate (ATP). Yeast contains enzymes that catalyze the breakdown of glucose. The energy stored in ATP is used by cells to provide energy for growth and repair processes, active transport, and other important processes.

The amount of carbon dioxide gas released is dependent on the amount of food (in this experiment, sugar) used by the yeast for growth and reproduction. To determine the amount of carbon dioxide produced during the experiment, the amount of inflation of a balloon will be observed. The more the balloon inflates, the more carbon dioxide is produced by the yeast.

Questions & Answers:

• Why would having a sweet tooth be evolutionary advantageous?
  • Scientific literature suggests that having a preference for sweet foods, especially in children, is not just a result of modern-day food processing and advertising but a reflection of basic biology.
  • High preference for sweet-tasting foods and beverages during childhood is universal and evident among infants and children around the world. The liking for sweet tastes during development may have ensured the acceptance of sweet-tasting foods, such as mother's milk and fruits.
  • Moreover, recent research suggests that liking for sweets may be further promoted by the pain-reducing properties of sugars.
• What could be other variables we could test using this method?
  • Using different sugar types (Splenda, Stevia, brown sugar)
  • Using uncarbonated soda syrup
  • Temperature
  • Varying the amount of sugar added to the bottles
  • Quantifying the amount of gas produced using a gas pressure sensor

Applications to Everyday Life: Explain (don't just list) three instances where this principle can be used to explain other phenomenon.

• Our body need energy to work. This energy comes from the food we eat. Our bodies digest the food we eat by mixing it with the acidic fluids and enzymes in our stomach. The carbohydrates in the food are broken down into another type of sugar, called glucose. The stomach and small intestines produce the glucose and then release it into the bloodstream. Once in the bloodstream, glucose can be used immediately for energy or stored in our bodies, to be used later.
• However, our bodies need insulin in order to use or store glucose for energy. Without insulin, glucose stays in the bloodstream, keeping blood sugar levels high
• Bread is made using flour, water, and yeast. As you knead the mixture, the enzymes in yeast begin to break down the large starch molecules in the flour down into glucose. If the dough well kneaded and has a strong and elastic feel, the carbon dioxide produced by the yeast will begin to rise the dough.
• Breweries use alcoholic fermentation to manufacture alcoholic beverages. This process is carried out by yeast cells in closed conditions. These yeast cells gain energy from the conversion of the sugar into carbon dioxide and ethanol. The carbon dioxide by-product bubbles through the liquid and dissipates into the air. The ethanol produced remains in the liquid but the yeast will die after too much ethanol is produced.

Collaborative Spreadsheet

Protocol adapted from American Society of Microbiology