We have interdisciplinary activities and tips to help. This brief guide will provide you with the information you need to make a number of solutions commonly used in educational laboratories. In this activity, students engage in a game of beanbag toss—but instead of merely keeping score, they explore statistical concepts such as mean, median, mode, and range.
This author provides an excellent student lab-report format, explains how it adapts to different science disciplines, and suggests simple labs to familiarize students with it. Keep your classroom or lab safe throughout the schoolyear with lots of helpful tips, hints, and safety techniques.
You have questions-we have answers. Get general information, care guides, and product information here. Brush up on the latest instructional strategies and pedagogy with information from our teaching partners, instructional designers, and academic consultants. Feeling the pinch from the current economy? Carolina understands. Cellular respiration and fermentation are 2 of the most challenging concepts for introductory biology students, who may become so consumed by memorizing steps of the Krebs cycle and glycolysis that they lose sight of the big picture.
The following demonstrations place aerobic cell respiration and fermentation firmly in grasp. First, students observe respiration in germinating seeds by detecting the carbon dioxide produced. Next, they observe the carbon dioxide gas produced by yeast fermentation. Have students observe the respiration of germinating seeds, using bromthymol blue as a pH indicator. You can keep this demonstration simple by observing pH changes in solution as seeds respire. Alternatively, you might add variables to the demonstration e.
Additionally, you can test whether photosynthesis is occurring by placing duplicate samples in the dark. Note: Wear gloves and safety goggles while handling the bromthymol blue solution and sodium hydroxide.
Have students consider the seeds' respiration. Oxygen is present in the test tube, and the carbon dioxide gas is a product of the process of aerobic cellular respiration. To a much lesser extent and for a limited time, germinating seeds may also perform anaerobic respiration, which also produces carbon dioxide.
Discuss the purpose of the control tube with only bromthymol blue solution. Students may think that the seeds are photosynthesizing.
If chlorophyll and light are present, the seeds may be photosynthesizing. Students should know that plants' photosynthesis uses carbon dioxide and produces oxygen. While additional oxygen would not significantly change the pH, removal of carbon dioxide from solution would make the solution more basic and turn the bromthymol blue a deeper blue color. Students observe the carbon dioxide gas produced as yeast ferments sugar. Suggested conditions to vary include the concentration of glucose, the sugar type, the temperature of incubation, and the amount of light.
The volume of carbon dioxide released is proportional to the quantity of sugar fermented and is therefore a measure of fermentation. Fermentation results from the action of enzymes. In yeast cells, enzymes convert sugars into carbon dioxide and ethanol.
A yeast can ferment a particular type of sugar only if the yeast cell contains the proper enzyme s to break down that molecule. Baker's yeast contains the enzymes to break down glucose and sucrose but not lactose or sucralose. We use cookies to provide you with a great user experience. By using our site, you accept our use of cookies. You can review our cookie and privacy policy here. Login or Register My Account Login or register now to maximize your savings and access profile information, order history, tracking, shopping lists, and more.
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Lab Equipment Carolina is your quality source for a well-equipped lab. Conversely, many prokaryotes are facultative, meaning that, should the environmental conditions change to provide an appropriate inorganic final electron acceptor for respiration, organisms containing all the genes required to do so will switch to cellular respiration for glucose metabolism because respiration allows for much greater ATP production per glucose molecule.
Some living systems use an organic molecule commonly pyruvate as a final electron acceptor through a process called fermentation. Fermentation does not involve an electron transport system and does not directly produce any additional ATP beyond that produced during glycolysis by substrate-level phosphorylation. Organisms carrying out fermentation, called fermenters, produce a maximum of two ATP molecules per glucose during glycolysis.
Table 1 compares the final electron acceptors and methods of ATP synthesis in aerobic respiration, anaerobic respiration, and fermentation. Microbial fermentation can also be useful for identifying microbes for diagnostic purposes.
Fermentation by some bacteria, like those in yogurt and other soured food products, and by animals in muscles during oxygen depletion, is lactic acid fermentation. The chemical reaction of lactic acid fermentation is as follows:. Bacteria of several gram-positive genera, including Lactobacillus , Leuconostoc , and Streptococcus , are collectively known as the lactic acid bacteria LAB , and various strains are important in food production.
During yogurt and cheese production, the highly acidic environment generated by lactic acid fermentation denatures proteins contained in milk, causing it to solidify. When lactic acid is the only fermentation product, the process is said to be homolactic fermentation ; such is the case for Lactobacillus delbrueckii and S. One important heterolactic fermenter is Leuconostoc mesenteroides , which is used for souring vegetables like cucumbers and cabbage, producing pickles and sauerkraut, respectively.
Lactic acid bacteria are also important medically. The production of low pH environments within the body inhibits the establishment and growth of pathogens in these areas. For example, the vaginal microbiota is composed largely of lactic acid bacteria, but when these bacteria are reduced, yeast can proliferate, causing a yeast infection. Additionally, lactic acid bacteria are important in maintaining the health of the gastrointestinal tract and, as such, are the primary component of probiotics.
Another familiar fermentation process is alcohol fermentation , which produces ethanol. The ethanol fermentation reaction is shown in Figure 1. In the first reaction, the enzyme pyruvate decarboxylase removes a carboxyl group from pyruvate, releasing CO 2 gas while producing the two-carbon molecule acetaldehyde. The ethanol fermentation of pyruvate by the yeast Saccharomyces cerevisiae is used in the production of alcoholic beverages and also makes bread products rise due to CO 2 production.
Outside of the food industry, ethanol fermentation of plant products is important in biofuel production. Figure 1. The chemical reactions of alcohol fermentation are shown here. Ethanol fermentation is important in the production of alcoholic beverages and bread.
Without these pathways, glycolysis would not occur and no ATP would be harvested from the breakdown of glucose. Many of these different types of fermentation pathways are also used in food production and each results in the production of different organic acids, contributing to the unique flavor of a particular fermented food product. The propionic acid produced during propionic acid fermentation contributes to the distinctive flavor of Swiss cheese, for example. Several fermentation products are important commercially outside of the food industry.
For example, chemical solvents such as acetone and butanol are produced during acetone-butanol-ethanol fermentation. Complex organic pharmaceutical compounds used in antibiotics e. Fermentation products are used in the laboratory to differentiate various bacteria for diagnostic purposes.
For example, enteric bacteria are known for their ability to perform mixed acid fermentation, reducing the pH, which can be detected using a pH indicator. Without a chemical analysis of the gas, they do not know. Also ask them how they know that if they created an identical test chamber of molasses solution, but without adding the yeast cells, they wouldn't get the same result - a gas bubble that grew over time. Until they've done the experiment they don't know.
These unknowns are why researchers use controls when they do experiments; controls enable them to rule out other explanations of their results. In this case, the control would be an identical test chamber set up without the addition of yeast cells, and placed alongside the experimental chambers in the rack for the duration of the experiment.
If a gas bubble appeared and grew over the next few days, it could not be concluded that the gas bubbles in the test chambers were due to yeast respiration. Instead, it would be more likely that a chemical reaction within the molasses solution produced the bubbles. But if no gas bubble appeared in the control chamber, the most likely explanation for the growing bubble in the test chambers would be the production of carbon dioxide by respiring yeast cells.
Concluding Discussion : Once the activity is done, lead a class discussion to share and compare results and conclusions. See details in the Procedure and Investigating Questions sections. Listen to student answers to gauge their level of comprehension. Writing Problem : At activity end, present to students the following scenario and ask them to write and turn in their responses for grading. Review their answers to assess their depth of comprehension. Several loaves of bread that a baker made this morning did not rise as they should have.
The result was flat, dense loaves that he cannot sell. He suspects a problem with the yeast, since he knows that it is the yeast that makes the bread dough rise. All of the yeast he used came from his one large supply. How can you help the baker determine if his yeasts are functioning properly?
If materials are prepared correctly and procedures are followed as instructed, expect all of the test tubes to show clear signs of yeast respiration. If gas bubbles are not produced, any of the following may have occurred:. Make Yogurt : Like yeasts, some bacteria respire anaerobically. Yogurt is produced when bacteria break down lactose, the sugar contained in milk, to obtain energy for their cellular activities. Lactic acid is produced as a by-product, and this is what gives plain yogurt its tart taste.
Have students conduct an Internet search to find a recipe that the class could make. Afterwards, students might enjoy bringing in flavorings and toppings for when they taste the finished product. DGE However, these contents do not necessarily represent the policies of the NSF, and you should not assume endorsement by the federal government.
Why Teach Engineering in K? Find more at TeachEngineering. Quick Look. Print this activity. Suggest an edit. Discuss this activity. Curriculum in this Unit Units serve as guides to a particular content or subject area. TE Newsletter. Subscribe to TE Newsletter. Summary Students set up a simple way to indirectly observe and quantify the amount of respiration occurring in yeast-molasses cultures. Each student adds a small amount of baking yeast to a test tube filled with diluted molasses.
Then a second, smaller test tube is placed upside-down inside the solution. As the yeast cells respire, the carbon dioxide they produce is trapped inside the inverted test tube, producing a growing bubble of gas that is easily observed and measured. Students are presented with the procedure for designing an effective experiment; they learn to think critically about experimental results and indirect observations of experimental events.
Engineering Connection Concepts covered in this activity are used in biomedical, chemical and environmental engineering. Grades 6 - 8 Do you agree with this alignment?
Within individual organisms, food moves through a series of chemical reactions in which it is broken down and rearranged to form new molecules, to support growth, or to release energy. Cellular respiration in plants and animals involve chemical reactions with oxygen that release stored energy.
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