Lab 6: Metabolic Pathways Notes
LAB 6: METABOLIC PATHWAYS
Overview
This lab session focuses on three significant metabolic pathways: respiration and photosynthesis in Euglena and fermentation in yeast. Since the respiration and photosynthesis experiment involves a 2-hour wait, students will perform the fermentation experiment to maximize lab time.
Lab vs. Lecture Timing
The lab activities will not delve into the same depth as the lecture material. Students should review corresponding textbook sections for detailed explanations, especially the figures which are crucial for understanding.
Lab 6 Activities
Activity 1: Measure respiration and photosynthesis in Euglena.
Activity 2: Measure fermentation in yeast.
Preparation: Complete exercises marked with a star before attending the lab.
PHOTOSYNTHESIS AND CELLULAR RESPIRATION IN EUGLENA
Objectives
Observe cellular respiration and photosynthesis in Euglena beads.
Big Picture
Investigate how Euglena can synthesize sugars through photosynthesis and how they respire, affecting agricultural yield.
Safety Protocols
Full PPE must be worn throughout the experiment due to the use of live cultures and glassware.
Metabolic Processes
Cellular Respiration: A process that consumes oxygen and glucose to produce carbon dioxide, ATP, and water. This process is divided into three main stages:
Glycolysis occurs in the cytoplasm, producing ATP and pyruvate from glucose.
Citric Acid Cycle takes place in the mitochondria and generates ATP, NADH, and FADH2.
Oxidative Phosphorylation occurs on the inner mitochondrial membrane where the bulk of ATP is produced.
Overall reaction:
Glucose + O2 → CO2 + ATP + H2O
Photosynthesis: Light energy, carbon dioxide, and water are converted into glucose and oxygen:
Light Reactions: Take place in thylakoid membranes creating ATP and NADPH while releasing oxygen by splitting water.
Calvin Cycle: Occurs in the stroma, where ATP and NADPH are used to fix CO2 into glucose.
Overall reaction:
H2O + light + CO₂ → glucose + O2
Investigative Questions
Can we observe cellular respiration in Euglena beads?
Can we observe photosynthesis in Euglena beads?
Conduct experiments to monitor carbon dioxide production/consumption under light and dark conditions. Phenol red will indicate pH changes related to carbon dioxide levels: yellow indicates acidity (CO2 is dissolved forming carbonic acid), red means basic (due to photosynthesis).
Expected Results: Data should be summarized in table format to indicate variations in oxygen and carbon dioxide under different conditions.
Materials Needed
Vials, Phenol red, sodium alginate beads containing Euglena.
SUGAR METABOLISM IN YEAST
Experiment Overview
Design, execute, and analyze an experiment testing fermentation of a substrate, specifically using Saccharomyces cerevisiae, yeast that can metabolize glucose anaerobically.
Safety Protocols
As yeast cultures are used, full PPE is necessary.
Fermentation Process
Glycolysis converts glucose to pyruvate, producing a net gain of 2 ATP.
In aerobic conditions, pyruvate turns into acetyl CoA, entering the citric acid cycle.
In anaerobic conditions, pyruvate undergoes fermentation leading to ethanol and CO2 production. This process regenerates NAD+, necessary for continued glycolysis.
Overall fermentation reaction:
Glucose → 2 Ethanol + 2 CO2 + 2 ATP
Physiological Response Curve
Create a curve that represents yeast's reactions to nutrient substrates over time:
Lag Phase: Time taken for reactions to start.
Log Phase: Rapid reaction rates.
Stationary Phase: Reaction plateaus due to end product accumulation.
Death Phase: Reaction declines as substrates diminish.
Experiment Design
Use Durham tubes to measure CO2 produced by yeast fermentation.
Select one or two substrates (corn syrup, kernel extract, etc.) to observe fermentation rates.
Label and prepare tubes with your selected substrates before mixing in the yeast suspension.
Cleanup
Follow specified protocols for cleaning to ensure lab safety and orderliness, including rinsing and storing equipment immediately after use.
Reflective Questions
Was the experimental design valid? What changes would improve its reliability?
How does the experiment correlate with real-world applications, including biofuel production?
What follow-up studies could be conducted to explore resulting data more deeply?
Conclusion
Understanding these metabolic pathways through laboratory experiments sheds light on vital biological processes. Recognizing the balance between respiration and photosynthesis in plants, as well as fermentation in yeast, illustrates the interconnectedness vital for life on Earth. Such knowledge is fundamental in fields like agriculture and bioengineering, where applications are increasingly relevant in addressing food and energy challenges.
LAB 6: METABOLIC PATHWAYS
Overview
This lab session focuses on three important metabolic pathways: respiration and photosynthesis in Euglena and fermentation in yeast. Understanding these processes is crucial for both ecology and agriculture since they help transfer energy and cycle carbon in ecosystems. Because measuring respiration and photosynthesis takes about 2 hours, students will do the fermentation experiment at the same time to make the most of the lab period.
Lab vs. Lecture Timing
The lab activities will not go into as much detail as the lecture material. Students should read related sections in the textbook for more information, especially the figures, which are essential for understanding the complex processes involved.
Lab 6 Activities
Activity 1: Measure respiration and photosynthesis in Euglena.
Use special equipment to track changes in oxygen and carbon dioxide levels.
Activity 2: Measure fermentation in yeast.
Create a controlled experiment to see how different substrates affect fermentation rates.
Preparation: Complete starred exercises in advance to prepare for practical work during the lab.
PHOTOSYNTHESIS AND CELLULAR RESPIRATION IN EUGLENA
Objectives
Observe how Euglena beads perform cellular respiration and photosynthesis. Understand the biochemical processes involved and their significance in ecology.
Big Picture
Investigate how Euglena creates sugars using photosynthesis and how they respire, highlighting their roles in aquatic ecosystems and their effects on agricultural yields by increasing biomass.
Safety Protocols
Wear full PPE (Personal Protective Equipment), which includes gloves, goggles, and lab coats, during the experiment to ensure safety when handling live cultures and glassware.
Metabolic Processes
Cellular Respiration: This is a biological process that uses oxygen and glucose to produce carbon dioxide, ATP (adenosine triphosphate), and water. It is vital for providing energy for cellular functions and is divided into three main stages:
Glycolysis happens in the cytoplasm, converting glucose to pyruvate and producing ATP through a series of enzyme-driven reactions.
Citric Acid Cycle occurs in mitochondria, where pyruvate is processed, producing ATP, NADH, and FADH2, which are crucial for the next phase.
Oxidative Phosphorylation occurs on the inner mitochondrial membrane, using electron transport chains to generate most of the ATP by making a proton gradient.
Overall reaction:
Glucose + O2 → CO2 + ATP + H2O
Photosynthesis: This process transforms light energy, carbon dioxide, and water into glucose and oxygen, which is key for energy capture in ecosystems:
Light Reactions: These take place in thylakoid membranes, converting light energy into ATP and NADPH while releasing oxygen from splitting water.
Calvin Cycle: Happens in the stroma of chloroplasts, utilizing ATP and NADPH to fix CO2 into glucose through specific enzymatic reactions.
Overall reaction:
H2O + light + CO₂ → glucose + O2
Investigative Questions
Can we see how cellular respiration works in Euglena beads in a controlled setting?
Can we observe photosynthesis taking place in Euglena beads under different light conditions?
Run experiments to track carbon dioxide production or consumption in light and dark conditions. Phenol red will be used as a pH indicator, changing color based on carbon dioxide levels: yellow indicates acidity (from dissolved CO2 forming carbonic acid), and red shows a more basic environment (resulting from photosynthesis producing oxygen and reducing CO2).
Expected Results: Data should be formatted in a table to show changes in oxygen and carbon dioxide levels under various conditions.
Materials Needed
Vials, Phenol red, sodium alginate beads containing Euglena,
A light source to promote photosynthesis, a pH meter for accurate measurements.
SUGAR METABOLISM IN YEAST
Experiment Overview
Design, carry out, and analyze an experiment to test how yeast, specifically Saccharomyces cerevisiae, ferments a substrate. This yeast can process glucose without oxygen, making it important for many industrial uses.
Safety Protocols
Full PPE is required when working with yeast cultures to ensure safety and minimize exposure to biological materials.
Fermentation Process
Glycolysis converts glucose to pyruvate, leading to a net gain of 2 ATP, which is crucial for energy in anaerobic conditions.
In aerobic conditions, pyruvate becomes acetyl CoA, entering the citric acid cycle for further energy extraction.
In anaerobic conditions, pyruvate goes through fermentation, resulting in the production of ethanol and CO2. This process also regenerates NAD+, allowing glycolysis to continue, which is essential for yeast to survive without oxygen.
Overall fermentation reaction:
Glucose → 2 Ethanol + 2 CO2 + 2 ATP
Physiological Response Curve
Create a graph showing how yeast reacts to different nutrient sources over time:
Lag Phase: The initial period when cells adjust to their environment.
Log Phase: When cells grow quickly and fermentation happens fast.
Stationary Phase: A point where reaction rates level off due to the buildup of end products and limited substrates.
Death Phase: A decline in reactions occurs as substrates become scarce and toxic byproducts accumulate.
Experiment Design
Use Durham tubes to measure CO2 produced by yeast fermentation; this provides a quantifiable measure of fermentation activity.
Choose one or two substrates (corn syrup, kernel extract, molasses, etc.) to see how they affect fermentation rates, showing how different types influence yeast activity.
Label and prepare tubes with your chosen substrates and controls before adding the yeast suspension to ensure accurate results.
Cleanup
Follow specific cleanup protocols to maintain lab safety and organization, including the proper disposal of biological waste, cleaning and storing equipment promptly after use, and keeping the workspace tidy throughout the experiments.
Reflective Questions
Was the experimental design solid? What changes could enhance its reliability and repeatability?
How does this experiment relate to real-world applications like biofuel production and in the food industry?
What follow-up studies could delve deeper into the data collected, taking into account different environmental factors or yeast strains?
Conclusion
Understanding these metabolic pathways through well-structured lab experiments not only enhances knowledge about key biological processes but also underscores the balance between respiration and photosynthesis in plants, alongside fermentation in yeast. This knowledge illustrates how interconnected metabolic functions are essential for life on Earth. Insights gained here are critical in agriculture and bioengineering, where they contribute to solutions for food and energy challenges, guiding sustainable practices for the future.