methylene blue yeast respiration experiment temperature

Want to adapt books like this? Learn more about how Pressbooks supports open practices.

8 Chapter 8 – Respiration

Respiration by yeast.

During respiration, yeast undergo metabolic processes to obtain energy from the breakdown of sugars. However, yeast can only metabolize certain types of sugars. In order for yeast to utilize a particular sugar as a food source, it needs to have specific transport mechanisms to bring the sugar molecules into its cells. Additionally, the yeast must possess the necessary enzymes capable of breaking down the chemical bonds in the sugar molecules in a way that can be used for energy production.

Among the various sugars, glucose is an essential source of energy for all living organisms, including yeast. Yeast can metabolize glucose through two different pathways: aerobic respiration and anaerobic fermentation. In aerobic respiration , yeast utilize oxygen to break down glucose molecules completely, resulting in the production of carbon dioxide (CO 2 ) and water (H 2 O) as byproducts. This process is highly efficient and yields a larger amount of energy in the form of ATP (adenosine triphosphate).

On the other hand, yeast can also carry out anaerobic respiration in the absence of oxygen. This process, known as fermentation, allows yeast to partially break down glucose molecules, resulting in the production of ethanol (alcohol) and carbon dioxide as byproducts. Although fermentation provides yeast with energy, it is less efficient compared to aerobic respiration.

In this lab, the objective is to investigate the ability of yeast to metabolize different sugars and observe respiration rate . The four sugars being tested are glucose, sucrose , fructose , and lactose . The experiment involves using a CO 2 Gas Sensor to measure the production of carbon dioxide by yeast as they respire using these sugars. The production of carbon dioxide indicates the metabolic activity of the yeast and provides insight into their ability to utilize the tested sugars as a food source.

By observing the rate and amount of carbon dioxide produced by the yeast when exposed to each sugar, it is possible to determine which sugars can be effectively metabolized by the yeast. This information helps in understanding the metabolic preferences and capabilities of yeast in utilizing different sugars for energy production.

• Respiration rate

 Objectives

• Use a C0 2 Gas Sensor to measure concentrations of carbon dioxide.
• Determine the rate of respiration by yeast while using different sugars.
• Determine which sugars can be used as a food source by yeast.
• Vernier LabQuest 2 device
• Water bath @ 38-40 °C
• Vernier C02 Gas Sensor (2)
• Test tube rack
• Yeast Suspension*
• Deionized water
• 10x100mm test tubes (5)
• 5% Glucose, Sucrose, Lactose, and Fructose sugar solutions
• Disposable pipettes OR p-1000 Micropipettes with tips
• 250ml respiration chamber or Erlenmeyer flask (5)

*Stock solution of yeast: 7g of yeast (1 packet) in 100 mL water prepared fresh for the class, placed in 38-40 °C water bath for 10 minutes.

Pre-Assessment

1. What is the purpose of investigating the ability of yeast to metabolize different sugars in the lab? 2. How does yeast obtain energy from the breakdown of sugars during respiration? 3. What are the specific requirements for yeast to utilize a particular sugar as a food source? 4. Which sugar is considered an essential source of energy for all living organisms, including yeast? 5. What are the two pathways through which yeast can metabolize glucose? 6. Describe the byproducts produced during aerobic respiration of glucose by yeast. 7. What is the difference between aerobic respiration and anaerobic fermentation in yeast? 8. How does the efficiency of energy production differ between aerobic respiration and anaerobic fermentation in yeast? 9. What is the role of the CO 2 Gas Sensor in the lab experiment? 10. How can observing the rate and amount of carbon dioxide produced by yeast when exposed to different sugars help determine their metabolic preferences and capabilities?

• Prepare a water bath for the yeast. A water bath is simply a large reservoir of water at a certain temperature. This ensures that the yeast will remain at a constant and controlled temperature. Make sure the digital water bath has several inches of water in the basin. Turn the water bath on and set the temperature at 38-40°C. Monitor the temperature of the water bath during the experiment.
• Connect the C0 2 Gas Sensor to the LabQuest 2 device: Insert the plug into the CHI port at the left side of the device. Set the sensor switch to low (0 – 10,000 ppm) setting. Turn on the LabQuest 2 by pressing the button at the top left of the device.
• To clear any unwanted data from the device before beginning the experiment, tap ‘File’, then select ‘New’ from the drop down menu. When prompted, tap ‘Discard’.
• Obtain five test tubes and label them G, S, F, L, and W.
• Place 3 mL of the glucose solution in test tube G.
• Place 3 mL of the sucrose solution in test tube S.
• Place 3 mL of the fructose solution in test tube F.
• Place 3 mL of the lactose solution in test tube L.
• Place 3 mL of deionized water in test tube W.
• Obtain 15 mL of the yeast suspension. Gently swirl the yeast suspension to mix the yeast that settles to the bottom.
• Put 2 mL of the yeast suspension into the test tube labeled G (glucose). Gently swirl the test tube to mix the yeast into the solution.
• Set the test tube into the water bath and incubate for 10 minutes.
• When incubation is finished, use a pipet to place 3 mL of the solution from test tube G into the 250 mL respiration chamber or flask. Note the temperature of the water bath and record as the actual temperature in Table 1.
• Quickly place the shaft of the C0 2 Gas Sensor in the opening of the respiration chamber or flask. Gently twist the stopper on the shaft of the C0 2 Gas Sensor into the chamber opening. Do not twist the shaft of the C0 2 Gas Sensor or it could be damaged.
• Begin measuring the carbon dioxide concentration by tapping the green arrow ( at the bottom left of the screen. Collect data for 4 minutes (240 seconds), then press the red square to stop data collection. Pressing the arrow button on the right of the device will also start and stop data collection.
• A graph of C0 2 production over time will be displayed. Move your data to a stored run. To do this, tap on the filing cabinet icon at the top right of the screen.
• When data collection has finished, remove the C0 2 Gas Sensor from the respiration chamber. Use a notebook or notepad to fan air across the openings in the probe shaft of the C0 2 Gas Sensor for 1 minute.
• Repeat Steps 7 – 13 for the other four test tubes. Each run will be graphed a different color with a different shape for the data points (square, triangle, circle). It is a good idea to write down which graph represents which sugar.
• When data for all five tubes has been collected and stored, tap the screen next to the filing cabinet icon where it says ‘Run’. Select ‘All Runs’. The graphs for each sugar tested will be displayed.
• Tap ‘Analyze’ from the top of the screen.
• Select ‘Curve Fit’ from the drop-down menu. Select the square for the first sugar tested.
• Tap the arrow next to ‘Choose Fit’ and select ‘Linear’. The formula for a best fit line will appear (y = mx + b).
• RECORD THE SLOPE OF THE LINE (m) AS THE RATE OF RESPIRATION IN TABLE 1. The rate of respiration given by m on the graph is in ppm/s. This should be converted to ppm/min for Table 1.
• Tap OK at the bottom right. This displays the best fit line on the graph.
• Determine the slope of the line (m) for each of the sugars by repeating steps 1 through 5, selecting the next square for the next sugar tested.
• Name (Bench #) and save your file
• Insert your USB (if LabQuest2 does not register the USB, ensure the USB is inserted properly)
• Highlight your named file and continue.
• It is now safe to remove the USB once exporting is complete.
• Upload your file to a device and make sure the entire group has a copy. You can use this file for data manipulation.
• Upload the data into the Respiration discussion board on Canvas.
• Clear the data by tapping ‘File’ and selecting ‘New’. Tap ‘Discard’ when prompted.
• Press the button on the device with the house icon.
• Select (System’, then ‘Shut Down’.
• Tap ‘OK’ when prompted.
• Return sensors and LabQuest 2 to the cart. Wash all glassware.

DATA ANALYSIS & CRITICAL THINKING QUESTIONS

• (Optional) When all other groups have posted their results on the board, calculate the average rate of respiration for each solution tested. Record the average rate values in Table 2.
• Make a bar graph of rate of respiration vs. sugar type. The rate values should be plotted on the y-axis, and the sugar type on the x-axis. Use the rate values from Table 1.
• Considering the results of this experiment, do yeast equally utilize all sugars? Explain.
• Hypothesize why some sugars were not metabolized while other sugars were.
• Why do you need to incubate the yeast before you start collecting data?
• Yeast live in many different environments. Make a list of some locations where yeast might naturally grow. Estimate the possible food sources at each of these locations.

Licenses and Attributions

Yeast is a type of fungus belonging to the kingdom Fungi. It is a single-celled microorganism that plays a significant role in various biological processes, especially in the context of fermentation and baking. Yeast cells are eukaryotic, meaning they possess a true nucleus and other membrane-bound organelles.

Yeast is widely used in the food and beverage industry, particularly in baking and brewing. It has been utilized by humans for thousands of years for the fermentation of sugars, which results in the production of carbon dioxide, ethanol, and other metabolic byproducts. This fermentation process is essential in the leavening of bread, where carbon dioxide gas produced by yeast causes the dough to rise, resulting in a light and fluffy texture.

The most commonly used species of yeast in baking and brewing is Saccharomyces cerevisiae. It has the ability to metabolize various sugars, including glucose, sucrose, fructose, and lactose, through the process of respiration. Yeast cells break down these sugars to obtain energy in the form of ATP (adenosine triphosphate), which is the primary energy currency of cells.

Apart from its role in fermentation, yeast also serves as a model organism in biological research. Due to its simple and well-studied genetics, yeast has provided valuable insights into various cellular processes and molecular mechanisms. Researchers have used yeast to study fundamental biological phenomena, such as cell cycle regulation, DNA replication, protein synthesis, and aging.

Yeast cells reproduce asexually through a process called budding, where a small bud or protrusion forms on the parent cell and eventually separates to become a new individual. Under certain conditions, yeast can also undergo sexual reproduction, involving the fusion of two yeast cells and the exchange of genetic material.

In summary, yeast is a single-celled fungus that plays a vital role in fermentation, baking, brewing, and scientific research. Its ability to metabolize sugars and produce carbon dioxide and ethanol has made it an indispensable microorganism in the food and beverage industry. Additionally, yeast's genetic simplicity and biological characteristics have made it a valuable model organism for understanding fundamental biological processes.

Glucose is a simple sugar and one of the most important carbohydrates in biological systems. It is a primary source of energy for living organisms and plays a crucial role in cellular metabolism. Glucose is a monosaccharide, which means it consists of a single sugar molecule. Its chemical formula is C6H12O6.

Glucose is found in various forms and sources in nature. Some common examples include:

1. Blood sugar: Glucose is the main sugar found in the bloodstream of animals, including humans. It is transported through the bloodstream to provide energy to cells throughout the body.

2. Plant sap: Glucose is present in the sap of plants, which serves as a nutrient-rich fluid that transports sugars and other substances within the plant's vascular system.

3. Fruits: Many fruits contain glucose, often in combination with other sugars like fructose. Fruits such as grapes, bananas, apples, and oranges are examples of glucose-containing fruits.

4. Honey: Bees produce honey by converting nectar, a sugary liquid found in flowers, into a concentrated solution. Honey contains glucose as well as other sugars.

5. Starches: Glucose molecules are the building blocks of starch, a polysaccharide found in various plant-based foods. Starchy foods like potatoes, rice, wheat, and corn contain glucose in the form of long chains of starch molecules.

6. Sweeteners: Glucose is used as a sweetener in various food products. It is commonly found in syrups like corn syrup and high-fructose corn syrup, which are widely used in the food industry.

7. Metabolism: Glucose is produced through the breakdown of more complex carbohydrates, such as glycogen (the storage form of glucose in animals) and starches, during digestion. It is then used by cells as a fuel source through processes like glycolysis and cellular respiration.

Glucose is an essential energy source for organisms and serves as a fundamental component in many biological processes. Its availability and regulation in the body are crucial for maintaining normal physiological functions.

Aerobic metabolism of sugar refers to the process by which cells, including yeast cells, break down sugar molecules in the presence of oxygen to produce energy. This process is also known as cellular respiration and occurs in several sequential steps.

The first step in aerobic metabolism is glycolysis, which takes place in the cytoplasm of the cell. During glycolysis, a molecule of glucose, a six-carbon sugar, is converted into two molecules of pyruvate, a three-carbon compound. This process involves the breakdown of glucose into smaller molecules, releasing a small amount of ATP (adenosine triphosphate) and NADH (nicotinamide adenine dinucleotide, a coenzyme) as byproducts.

After glycolysis, if oxygen is available, the pyruvate molecules produced are transported into the mitochondria, the powerhouses of the cell. In the mitochondria, the pyruvate molecules undergo further oxidation in a process called the citric acid cycle, also known as the Krebs cycle or TCA (tricarboxylic acid) cycle. The citric acid cycle involves a series of chemical reactions that break down the pyruvate molecules, releasing more ATP, NADH, and FADH2 (flavin adenine dinucleotide, another coenzyme).

The NADH and FADH2 molecules produced during glycolysis and the citric acid cycle play a crucial role in the final step of aerobic metabolism: oxidative phosphorylation. Oxidative phosphorylation occurs in the inner mitochondrial membrane and involves the transfer of electrons from NADH and FADH2 to a series of protein complexes known as the electron transport chain (ETC). As electrons pass through the ETC, they release energy that is used to pump protons (H+) across the inner mitochondrial membrane, creating an electrochemical gradient.

The electrochemical gradient created by the ETC drives the synthesis of ATP through a process called chemiosmosis. ATP synthase, an enzyme located in the inner mitochondrial membrane, utilizes the energy from the proton gradient to produce ATP. This process is known as oxidative phosphorylation because it couples the phosphorylation of ADP (adenosine diphosphate) to form ATP with the oxidation of NADH and FADH2.

Overall, aerobic metabolism of sugar provides the most efficient way to produce energy in cells. It yields a large amount of ATP compared to anaerobic processes like fermentation. By utilizing oxygen, cells can fully break down sugar molecules, extracting maximum energy from them and generating carbon dioxide and water as byproducts. This process is essential for the functioning and survival of cells, including yeast cells, in oxygen-rich environments.

Anaerobic metabolism of sugar, also known as fermentation, is a metabolic pathway that allows cells to generate energy from sugar molecules in the absence of oxygen. Unlike aerobic metabolism, which occurs in the presence of oxygen and yields more energy, anaerobic metabolism is less efficient and produces fewer ATP molecules.

There are several types of anaerobic fermentation, but one of the most common forms is alcoholic fermentation, which occurs in yeast and some bacteria. In this process, glucose or other sugars are converted into ethanol (alcohol) and carbon dioxide.

The first step of anaerobic metabolism is glycolysis, which takes place in the cytoplasm of the cell. During glycolysis, a molecule of glucose is broken down into two molecules of pyruvate, similar to the process in aerobic metabolism. This step releases a small amount of ATP and NADH.

In the absence of oxygen, pyruvate molecules undergo further conversion through fermentation. In the case of alcoholic fermentation, pyruvate is decarboxylated, meaning it loses a carbon dioxide molecule, to form acetaldehyde. This reaction is catalyzed by the enzyme pyruvate decarboxylase. Simultaneously, NADH is oxidized back to NAD+ by transferring its electrons to the acetaldehyde, producing NAD+ and NADH. Acetaldehyde then undergoes a second reaction, catalyzed by the enzyme alcohol dehydrogenase, where it is reduced by NADH to produce ethanol. This final step regenerates NAD+ for further glycolysis to continue.

The overall process of anaerobic metabolism of sugar is less efficient than aerobic metabolism because it produces only a small amount of ATP. In addition to ethanol, carbon dioxide is also produced as a byproduct. This is why during alcoholic fermentation, we observe the release of carbon dioxide bubbles.

Anaerobic metabolism is important for organisms that live in environments with low oxygen availability. It allows them to continue producing energy even when oxygen is limited or absent. For example, yeast cells undergo anaerobic metabolism when fermenting sugars in the absence of oxygen, which is utilized in the production of alcoholic beverages and bread-making.

It's important to note that different organisms can undergo other types of anaerobic fermentation, such as lactic acid fermentation in some bacteria and human muscle cells. These processes involve different intermediate compounds and produce lactic acid instead of ethanol as the end product.

Respiration rate refers to the rate at which an organism or a cell undergoes cellular respiration, which is the process of breaking down organic molecules, such as sugars, to produce energy in the form of ATP (adenosine triphosphate). In the case of yeast, respiration rate specifically refers to the rate at which yeast cells carry out the process of cellular respiration.

Yeast cells are capable of metabolizing sugars through aerobic respiration, which occurs in the presence of oxygen, or anaerobic respiration, which occurs in the absence of oxygen. Both forms of respiration involve the breakdown of sugar molecules to release energy.

During aerobic respiration, yeast cells convert glucose, sucrose, fructose, lactose, or other sugars into carbon dioxide (CO2) and water (H2O). This process involves a series of enzymatic reactions that occur in the mitochondria of yeast cells. Oxygen is used as the final electron acceptor in the electron transport chain, allowing for the efficient production of ATP.

In contrast, during anaerobic respiration, yeast cells can metabolize sugars without the presence of oxygen. Instead of utilizing oxygen as the final electron acceptor, yeast cells undergo a process called fermentation. In this process, sugar molecules are partially broken down, producing alcohol (typically ethanol) and carbon dioxide as byproducts. This type of respiration is commonly observed in yeast when they are in an oxygen-deprived environment, such as when fermenting fruits to produce alcoholic beverages or when used in baking to make bread rise.

The respiration rate of yeast can be measured by monitoring the production of carbon dioxide gas. As yeast cells metabolize sugars, they release carbon dioxide as a byproduct, which can be detected and quantified using various methods, such as gas sensors or gas chromatography. By measuring the rate of carbon dioxide production, researchers can assess the metabolic activity and respiration rate of yeast under different conditions, such as varying sugar concentrations, temperatures, or pH levels.

Overall, the respiration rate of yeast provides insights into its metabolic activity, energy production, and ability to utilize different sugars as energy sources. It is an important parameter to consider when studying yeast physiology, fermentation processes, or when using yeast in various applications, such as brewing, winemaking, or biofuel production.

Sucrose is a disaccharide composed of glucose and fructose molecules linked together. It is commonly known as table sugar and is one of the most widely used sweeteners in the world. The chemical formula of sucrose is C12H22O11.

Sucrose is found in various natural sources and is commonly used as a sweetening agent in food and beverages. Here are some common examples of where sucrose is found:

1. Sugarcane: Sucrose is abundantly found in sugarcane plants. Sugarcane juice is extracted from the stalks of the plant and processed to obtain crystalline sucrose, which is further refined to produce table sugar.

2. Sugar beet: Sugar beet is another major commercial source of sucrose. The sucrose content is extracted from the root of the sugar beet plant and processed similarly to sugarcane to obtain sugar.

3. Fruits: Sucrose is naturally present in many fruits, although in varying amounts. Fruits like mangoes, pineapples, oranges, and strawberries contain sucrose along with other sugars like glucose and fructose.

4. Processed foods: Sucrose is widely used as a sweetener in processed foods such as baked goods, candies, desserts, soft drinks, and sauces. It provides sweetness and enhances the flavor of these products.

5. Condiments: Some condiments and spreads, such as jams, jellies, and syrups, contain sucrose to add sweetness and improve the taste.

6. Confectionery: Chocolates, candies, and confectionery products often contain sucrose as a primary sweetener. It contributes to the desirable taste and texture of these treats.

7. Beverages: Many beverages, including soda, energy drinks, and sweetened teas, contain sucrose for sweetening purposes.

Sucrose is widely consumed in the human diet and is a common ingredient in various culinary preparations. However, it is important to consume sucrose in moderation as excessive intake can contribute to health issues like obesity, dental problems, and metabolic disorders.

Fructose is a monosaccharide, or simple sugar, that is naturally occurring in many fruits, vegetables, and sweeteners. It is the sweetest of all naturally occurring sugars and has the same chemical formula as glucose (C6H12O6), but with a different arrangement of atoms.

Here are some key points about fructose and common examples of where it is found:

1. Natural Sources: Fructose is found in varying amounts in a wide range of fruits and vegetables. Some examples include:

- Fruits: Fructose is abundant in fruits such as apples, pears, grapes, cherries, peaches, and mangoes. It contributes to the natural sweetness of these fruits.

- Honey: Honey contains a mixture of fructose and glucose, with fructose being the predominant sugar. Bees convert nectar from flowers into honey, which is a concentrated source of fructose.

- Agave: Agave syrup, derived from the agave plant, is a popular natural sweetener that primarily consists of fructose. It is commonly used as an alternative to table sugar.

2. Processed Foods and Beverages: Fructose is also used as an added sweetener in various processed foods and beverages. High-fructose corn syrup (HFCS) is a common sweetener used in soft drinks, processed snacks, cereals, and baked goods. It is produced by enzymatically converting glucose from cornstarch into fructose, resulting in a sweeter and more economical alternative to sucrose (table sugar).

3. Sweeteners: Crystalline fructose, which is a highly pure form of fructose, is used as a sweetening agent in some food products. It is sweeter than sucrose and can be found in certain beverages, desserts, and low-calorie or sugar-free products.

It is worth noting that excessive consumption of fructose, particularly in the form of added sugars like high-fructose corn syrup, has been associated with potential health risks. High intake of fructose from processed foods and beverages has been linked to increased risk of obesity, type 2 diabetes, and metabolic disorders. As with any sugar, moderation is key when consuming fructose as part of a balanced diet.

Lactose is a disaccharide composed of two sugar molecules, glucose and galactose, linked together. It is commonly referred to as milk sugar because it is the primary sugar found in milk and dairy products. Lactose is unique in that it is primarily found in mammalian milk, including human breast milk.

Here are some key points about lactose and common examples of where it is found:

1. Milk and Dairy Products: Lactose is abundantly present in milk from various mammalian species, including cows, goats, and sheep. It serves as the main carbohydrate source in milk. Dairy products such as yogurt, cheese, butter, and ice cream also contain lactose, although the concentration may vary depending on the specific product.

2. Human Breast Milk: Lactose is an essential component of human breast milk, providing a source of energy for infants. It plays a crucial role in the development and growth of newborns. Human breast milk typically contains higher levels of lactose compared to the milk of other mammalian species.

3. Lactose-Containing Food Products: Lactose is sometimes used as an ingredient in processed food products, especially those aimed at individuals who are lactose intolerant. These products may include lactose-reduced or lactose-free dairy alternatives, lactose-free milk, lactose-free ice cream, and lactose-free yogurts.

4. Medications and Supplements: Lactose is also used as an excipient in some medications and dietary supplements. It can act as a filler or a binding agent in tablet or capsule formulations. Individuals with lactose intolerance or milk allergies should be cautious about consuming such products and may need to seek alternatives.

Lactose intolerance is a common condition where the body lacks sufficient amounts of the enzyme lactase, which is responsible for breaking down lactose into glucose and galactose for absorption in the small intestine. This leads to digestive symptoms, such as bloating, gas, and diarrhea, after consuming lactose-containing foods or beverages. As a result, individuals with lactose intolerance often need to limit or avoid foods high in lactose or use lactase supplements to aid in digestion.

It's important to note that lactose is not naturally present in non-dairy plant-based beverages like soy milk, almond milk, or coconut milk. These products are typically made by grinding or blending the respective plant material with water, without the addition of lactose.

Biology I Cellular Processes Laboratory Manual by The authors & Hillsborough Community College is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License , except where otherwise noted.

Share This Book

19. Investigation of dehydrogenase activity in yeast

• 00:22 Which molecules act as a hydrogen acceptors during aerobic respiration?
• 00:29 How will you adapt this method to investigate dehydrogenase activity in yeast?

redox indicator: methylene blue (0.05g/100cm 3 )

yeast suspension (100g/dm -3 )

30 o C Water bath

Cork for test tube

10 cm 3 syringe

1 cm 3 syringe

Your browser is not supported

Sorry but it looks as if your browser is out of date. To get the best experience using our site we recommend that you upgrade or switch browsers.

Find a solution

• Skip to main content
• Skip to navigation

• Back to parent navigation item
• Primary teacher
• Secondary/FE teacher
• Early career or student teacher
• Higher education
• Curriculum support
• Literacy in science teaching
• Periodic table
• Interactive periodic table
• Climate change and sustainability
• Resources shop
• Collections
• Remote teaching support
• Starters for ten
• Screen experiments
• Assessment for learning
• Microscale chemistry
• Faces of chemistry
• Classic chemistry experiments
• Nuffield practical collection
• Anecdotes for chemistry teachers
• On this day in chemistry
• Global experiments
• PhET interactive simulations
• Chemistry vignettes
• Context and problem based learning
• Journal of the month
• Chemistry and art
• Art analysis
• Pigments and colours
• Ancient art: today's technology
• Psychology and art theory
• Art and archaeology
• Artists as chemists
• The physics of restoration and conservation
• Ancient Egyptian art
• Ancient Greek art
• Ancient Roman art
• Classic chemistry demonstrations
• In search of solutions
• In search of more solutions
• Creative problem-solving in chemistry
• Solar spark
• Chemistry for non-specialists
• Health and safety in higher education
• Analytical chemistry introductions
• Exhibition chemistry
• Introductory maths for higher education
• Commercial skills for chemists
• Kitchen chemistry
• Journals how to guides
• Chemistry in health
• Chemistry in sport
• Chemistry in your cupboard
• Chocolate chemistry
• Adnoddau addysgu cemeg Cymraeg
• The chemistry of fireworks
• Festive chemistry
• Education in Chemistry
• Teach Chemistry
• On-demand online
• Live online
• Selected PD articles
• PD for primary teachers
• PD for secondary teachers
• What we offer
• Chartered Science Teacher (CSciTeach)
• Teacher mentoring
• UK Chemistry Olympiad
• Who can enter?
• How does it work?
• Resources and past papers
• Top of the Bench
• Schools' Analyst
• Regional support
• Education coordinators
• RSC Yusuf Hamied Inspirational Science Programme
• RSC Education News
• Supporting teacher training
• Interest groups

• More navigation items

The ‘blue bottle’ experiment

In association with Nuffield Foundation

• Four out of five

Transform methylthioninium chloride (Methylene blue) from blue to colourless and back again by mixing it with glucose and shaking the solution, then letting it settle

An alkaline solution of glucose acts as a reducing agent and reduces added methylene blue from a blue to a colourless form. Shaking the solution raises the concentration of oxygen in the mixture and this oxidises the methylene blue back to its blue form. When the dissolved oxygen has been consumed, the methylene blue is slowly reduced back to its colourless form by the remaining glucose, and the cycle can be repeated many times by further shaking.

Source: Colin Baker

The reactions involved are not generally part of the curriculum, but this experiment has a number of features that make it ideal for investigating reaction kinetics - it is very quick, the chemicals are relatively cheap and safe, and the measurements are straightforward. It also has great visual impact and so is a good way of stimulating interest in chemistry, perhaps via an open day.

The demonstration lasts 3–5 minutes, but 15–20 minutes is needed for the preparation beforehand.

• Eye protection: goggles should be worn when preparing the solution
• Conical flask (1 dm 3 )
• Stopper or bung, to fit flask
• Potassium hydroxide (CORROSIVE, IRRITANT), 8 g
• Glucose (dextrose), 10 g
• Methylene blue (HARMFUL), 0.05 g
• Ethanol (IDA – Industrial Denatured Alcohol) (HIGHLY FLAMMABLE, HARMFUL), 50 cm 3
• Access to a nitrogen cylinder (optional)

Health, safety and technical notes

• Read our standard health and safety guidance
• Eye protection. Wear goggles when preparing the solution.
• Potassium hydroxide, KOH(s), (CORROSIVE, IRRITANT) – see CLEAPSS Hazcard HC091b .
• Glucose (dextrose), C 6 H 12 O 6 (s) – see CLEAPSS Hazcard HC040c .
• Methylene blue (HARMFUL) – see CLEAPSS Hazcard HC032 .
• Ethanol (IDA – Industrial Denatured Alcohol), C 2 H 5 OH(l), (HIGHLY FLAMMABLE, HARMFUL) – see CLEAPSS Hazcard HC040a .

Before the demonstration

Less than 20 minutes beforehand, preferably.

• Make a solution of 0.05 g of methylene blue in 50 cm 3  of ethanol (0.1%).
• Weigh 8 g of potassium hydroxide into the 1 dm 3  conical flask.
• Add 300 cm 3  of water and 10 g of glucose and swirl until the solids are dissolved.
• Add 5 cm 3  of the methylene blue solution. The exact quantity used is not critical.
• The resulting blue solution will turn colourless after about one minute. Stopper the flask and label it IRRITANT (due to the potassium hydroxide present).

The demonstration

• Holding the stopper securely in place, shake the flask vigorously so that air dissolves in the solution.
• The colour will change to blue and will fade back to colourless over about 30 seconds.
• The more shaking, the longer the blue colour will take to fade.
• The process can be repeated for over 20 cycles.
• After some hours, the solution will turn yellow and the colour changes will fail to occur.

Go beyond …

Beyond the ’blue bottle’ offers another spectacular colour-change-in-a-bottle demonstration, using indigo carmine to produce a range of stunning colours.

To confirm that oxygen is responsible for the colour change, nitrogen can be bubbled through the solution for a couple of minutes to displace air from the solution and the flask. If the stopper is now replaced and the bottle shaken, no colour change will occur. Reintroducing the air by pouring the solution into another flask and shaking will restore the system. Natural gas can be used (in a fume cupboard) if nitrogen is not available.

Some teachers may wish to present this experiment as a magic trick . The colour change can be brought about by simply pouring the solution from a sufficient height into a large beaker.

• A white background helps to make the colour changes more vivid. A white laboratory coat is ideal.
• On a cold day it may be necessary to warm the solution to at least 20°C, otherwise the changes are very slow.
• This experiment can be a popular open day activity. If visitors are to be allowed to shake the bottle themselves it might be wise to use a plastic screw-top pop bottle to eliminate the risk of the stopper coming off or the bottle being dropped and broken. The solution does not appear to interact with the plastic over a period of a day but it would be sensible to try out the bottle you intend to use beforehand.

Teaching notes

Methylene blue is a redox indicator and is colourless under reducing conditions but regains its blue colour when oxidised.

The removal of the blue colour is caused by the glucose which, under alkaline conditions, is reducing the methylene blue to a colourless form. Shaking the solution admits oxygen, which re-oxidises the methylene blue back to the blue form.

This experiment could be used to determine the kinetics of the reaction and thus the mechanism.  

The reaction is first order with respect to the hydroxide ion, methylene blue and glucose but zero-order with respect to oxygen. The rate law can be found by measuring how long it takes for a solution of known concentration to go colourless.  

The activation energy can be calculated using a normal Arrhenius plot - natural logarithm of the decolouration time (ln t ) against the reciprocal of absolute temperature (1/ T ). Campbell 2  explains this can be done because the rate of the slow step is independent of the oxygen concentration, and thus the time,  t , which is required for the total oxygen to disappear, is directly related to the rate constant,  k . A straight line is obtained from the plot of ln t  against 1/ T . The rate law for the reaction is: 3

Rate =  k [Dox][CH][OH-] 

where Dox is the oxidised (blue) form of methylene blue and CH is the carbohydrate, glucose. A simple mechanism for the reaction is: 

CH + OH- ⇌ C- + H2O

O2 + D → Dox (Fast)

Dox + C- → D + X- (Slow) 

where D is the reduced (colourless) form of methylene blue and X- represents the oxidation products from glucose (arabinoic, formic, oxalic and erythronic acids). The enthalpy of the reaction has been reported as 23 kJ mol-1. 

Using other redox indicators

Redox indicators other than methylene blue can be used to present other colours and make the demonstration really striking. In each case add the stated amount of indicator to the basic recipe of 10 g of glucose and 8 g of potassium hydroxide in 300 cm 3  of water. Mixtures of the dyes can also be used.

Phenosafranine  

This is red when oxidised and colourless when reduced. Use about 6 drops of a 0.2% solution in water for a bottle that goes pink on shaking and colourless on standing. The initial pink colour takes some time to turn colourless at first. A mixture of phenosafranine (6 drops) and methylene blue (about 20 drops of the 0.1% solution in ethanol) gives a bottle which will turn pink on gentle shaking through purple with more shaking and eventually blue. It will reverse the sequence on standing.

Indigo carmine  

Use 4 cm 3  of a 1% solution in water. The mixture will turn from yellow to red-brown with gentle shaking and to pale green with more vigorous shaking. The changes reverse on standing. These colours are those of traffic lights. Find the full equipment list and procedure for the Traffic light demonstration in the Colour chemistry activities. 

Resazurin  

IRRITANT – see CLEAPSS Hazcard HC032. Use about 4 drops of a 1% solution in water. This goes from pale blue to a purple-pink colour on shaking and reverses on standing. On first adding the dye, the solution is dark blue. This fades after about one minute.

More resources

Inspire learners and discover more ways chemists are making a difference to our world with our video job profiles .

Additional information

This is a resource from the  Practical Chemistry project , developed by the Nuffield Foundation and the Royal Society of Chemistry.

Practical Chemistry activities accompany  Practical Physics  and  Practical Biology . 

The experiment is also part of the Royal Society of Chemistry’s Continuing Professional Development course: Chemistry for non-specialists .

© Nuffield Foundation and the Royal Society of Chemistry

• 11-14 years
• 14-16 years
• 16-18 years
• Demonstrations
• Redox chemistry
• Biological chemistry

Specification

• Many chemical reactions are reversible.
• 1. know that many reactions are readily reversible and that they can reach a state of dynamic equilibrium in which: the rate of the forward reaction is equal to the rate of the backward reaction; the concentrations of reactants and products remain…
• In some chemical reactions, the products of the reaction can react to produce the original reactants. Such reactions are called reversible reactions and are represented: A + B ⇌ C + D.
• Recall that some reactions may be reversed by altering the reaction conditions.
• 4.13 Recall that chemical reactions are reversible, the use of the symbol ⇌ in equations and that the direction of some reversible reactions can be altered by changing the reaction conditions
• C6.3.1 recall that some reactions may be reversed by altering the reaction conditions including: reversible reactions are shown by the symbol ; reversible reactions (in closed systems) do not reach 100% yield
• C6.3.1 recall that some reactions may be reversed by altering the reaction conditions including: reversible reactions are shown by the symbol ⇌; reversible reactions (in closed systems) do not reach 100% yield
• C5.2a recall that some reactions may be reversed by altering the reaction conditions
• C5.3a recall that some reactions may be reversed by altering the reaction conditions
• A reaction or process that releases heat energy is described as exothermic.
• Choice of indicator.
• Introduction to oxidation and reduction: simple examples only, e.g. Na with Cl₂, Mg with O₂, Zn with Cu²⁺.
• Oxidising and reducing agents.

Related articles

4 ways to teach redox in terms of electrons

2024-07-03T05:06:00Z By Kristy Turner

Use these teacher-tested approaches to help learners gain a deeper understanding of redox reactions

Why are some plants poisonous to you and your pets?

2024-05-22T08:16:00Z By Kit Chapman

Dig up the toxic secrets of nature’s blooms

Mastering titration apparatus

2024-05-07T08:38:00Z By Kristy Turner

Use this poster, fact sheet and classroom activity to show learners the names and uses of equipment they’ll encounter in this practical 

1 Reader's comment

Only registered users can comment on this article., more experiments.

‘Gold’ coins on a microscale | 14–16 years

By Dorothy Warren and Sandrine Bouchelkia

Practical experiment where learners produce ‘gold’ coins by electroplating a copper coin with zinc, includes follow-up worksheet

Practical potions microscale | 11–14 years

By Kirsty Patterson

Observe chemical changes in this microscale experiment with a spooky twist.

Antibacterial properties of the halogens | 14–18 years

By Kristy Turner

Use this practical to investigate how solutions of the halogens inhibit the growth of bacteria and which is most effective

• Contributors
• Email alerts

Site powered by Webvision Cloud

Respiration in Cells ( CIE IGCSE Biology )

Revision note.

Uses of energy released in respiration

What is respiration.

• Respiration is enzyme-controlled
• Much less energy is released for each glucose molecule broken down anaerobically compared to the energy released when it is broken down aerobically
• Respiration occurs in all living cells ; most of the chemical reactions in aerobic respiration take place in the mitochondria
• Muscle contraction
• Protein synthesis
• Cell division (to make new cells)
• Active transport across cell membranes
• Generation of nerve impulses
• Maintaining a constant internal body temperature

The energy released during respiration is used to fuel many processes in the human body

Avoid the common misconception that respiration is breathing! Respiration is a series of chemical reactions that release energy from glucose inside cells. Be careful that you always state that energy is released , it is NEVER made, produce, or created.

The respiration reactions are all controlled by enzymes. You need to be able to state this in an exam!

The effect of temperature on respiration

Respiration in yeast.

• An indicator can be used to investigate the effect of temperature  on the rate of aerobic respiration in yeast
• Methylene blue dye is a suitable indicator
• This dye can be added to a suspension of living yeast cells because it doesn't damage cells
• Yeast can respire both aerobically and anaerobically, though in this experiment it is their rate of aerobic respiration that is being investigated
• The faster the dye changes from blue to colourless, the faster the rate of respiration
• Yeast suspension
• Glucose solution
• Methylene blue
• Temperature-controlled water bath(s)

Methylene blue is added to a solution of aerobically respiring yeast cells in a glucose suspension. The rate at which the solution turns from blue to colourless gives a measure of the rate of aerobic respiration.

Independent and dependent variables

• Here the investigation studies the effect of temperature on respiration rate in yeast, so the independent variable is temperature
• Different temperatures are achieved using water baths
• In an investigation into the effect of temperature on the rate of respiration in yeast, the rate of respiration is the dependent variable
• The rate is measured here by recording the time taken for methylene blue dye to change from blue to colourless

Controlling other variables

• Volume/concentration of dye added : if there are more dye molecules present then the time taken for the colour change to occur may be longer
• Volume/concentration of yeast suspension : if more yeast cells are present then more respiration will be occurring and the dye will change colour more quickly
• Concentration of glucose : if there is limited glucose in one tube then the respiration of those yeast cells will be limited
• A buffer solution can be used to control the pH level to ensure that no enzymes are denatured
• It is also possible to convert 'time for colour change' into a unit of reaction rate; this has been done in the graph shown below
• Raising the temperature of a solution gives the molecules in the solution more kinetic energy, so they move around more and the enzymes and substrates involved in respiration collide with each other more frequently
• Increasing the temperature above a certain point causes the enzymes involved in respiration to denature; the shape of their active site changes and they can no longer form enzyme-substrate complexes

Temperature and the rate of respiration in yeast graph

The time taken for methylene blue to change colour can be converted into 'rate of respiration' and plotted on a graph. Note that a graph of temperature against 'time for colour change' will look different to the graph shown here.

You've read 0 of your 10 free revision notes

Get unlimited access.

to absolutely everything:

• Downloadable PDFs
• Unlimited Revision Notes
• Topic Questions
• Past Papers
• Model Answers
• Videos (Maths and Science)

Join the 100,000 + Students that ❤️ Save My Exams

the (exam) results speak for themselves:

Did this page help you?

Author: Phil

Phil has a BSc in Biochemistry from the University of Birmingham, followed by an MBA from Manchester Business School. He has 15 years of teaching and tutoring experience, teaching Biology in schools before becoming director of a growing tuition agency. He has also examined Biology for one of the leading UK exam boards. Phil has a particular passion for empowering students to overcome their fear of numbers in a scientific context.

Methylene blue/yeast practical

Quick reply, related discussions.

• Which of the functional groups consist only of carbon and hydrogen?
• PAG 12 OCR A Biology
• Oxidation of ethanol
• Practical: How to keep temperature constant?
• Alevel Practicals OCR A
• biology mitosis aqa alevel question
• SQA Higher Human Biology - Paper 2 - 15th May 2024 [Exam Chat]
• Edexcel GCSE Biology Paper 2 (Higher)(1B10/2H) - 7th June 2024 [Exam Chat]
• Colorimetry - BTEC applied science chemistry
• Applied Science Unit 3 investigation skills
• Make it More Bread-ey !!
• PAG 12 OCR biology A-Level
• Edexcel GCSE Chemistry Paper 2 Higher Tier 1CH0 2H - 20 Jun 2022 [Exam Chat]
• LAS Blue Light driving assessment 2 hours
• Similar shapes question
• chemistry inorganic reactions/colours/observations
• tips please!
• Helpful little memory tricks I use for AQA GCSE Biology
• Is it ok to use a pencil for rough working in an exam?
• Question about negative control pcr test!!!

Last reply 16 hours ago

Last reply 1 day ago

Last reply 2 days ago

Posted 6 days ago

Last reply 6 days ago

Last reply 1 week ago

Last reply 3 weeks ago

Posted 3 weeks ago

Posted 4 weeks ago

Last reply 4 weeks ago

Last reply 1 month ago

Posted 1 month ago

Last reply 2 months ago

Last reply 3 months ago

Articles for you

I want to go to uni but I don't know what to study

Expert tips on writing a great personal statement for law

What it’s really like qualifying as a solicitor through the SQE

What careers can a degree in policing lead to?