Metabolism: Anaerobic cellular respiration
- Anaerobic Cellular Respiration occurs in organisms when oxygen is not available to continue the process of Aerobic Cellular Respiration.
- When oxygen is limited, glycolysis would come to a halt if there were no alternative pathways. This is because NADH cannot be oxidized back to NAD+.
- Organisms have evolved many ways of dealing with this problem with one method being Fermentation.
- The two primary forms of fermentation used in eukaryotes are Ethanol Fermentation and Lactate (Lactic Acid) Fermentation.
CURRICULUM EXPECTATIONS
Overall Expectations
Specific Expectations
- C2. investigate the products of metabolic processes such as cellular respiration and photosynthesis;
- C3. demonstrate an understanding of the chemical changes and energy conversions that occur in metabolic processes
Specific Expectations
- C2.2 conduct a laboratory investigation into the process of cellular respiration to identify the products of the process, interpret the qualitative observations, and display them in an appropriate format
- C3.1 explain the chemical changes and energy conversions associated with the processes of aerobic and anaerobic cellular respiration
- C3.4 describe, compare, and illustrate (e.g., using flow charts) the matter and energy transformations that occur during the processes of cellular respiration (aerobic and anaerobic) and photosynthesis, including the roles of oxygen and organelles such as mitochondria and chloroplasts
Anaerobic Cellular Respiration Presentation
__anaerobicrespiration.pptx | |
File Size: | 10124 kb |
File Type: | pptx |
Content of this page is adapted from:
Di Giuseppe, M., Vavitsas, A., Ritter, B., Fraser D., Arora, A., and Lisser, B. (2003)Biology 12 Textbook, p. 117-124. Nelson Thomson Learning, Toronto.
Di Giuseppe, M., Vavitsas, A., Ritter, B., Fraser D., Arora, A., and Lisser, B. (2003)Biology 12 Textbook, p. 117-124. Nelson Thomson Learning, Toronto.
Anaerobic Pathways
Glycolysis allows organisms to obtain energy from nutrients in the absence of oxygen. However, step 6 (See diagram) of the glycolytic pathway reduces NAD+ to NADH. Cells possess a limited supply of NAD+. If glycolysis continues without a mechanism to oxidize NADH back into NAD+, step 6 will be blocked and glycolysis will come to a halt. In oxidative respiration, the ETC oxidizes NADH to NAD+, allowing glycolysis to continue.
Organisms have evolved several ways of recycling NAD+ and allowing glycolysis to continue when oxygen is not available. One method involves transferring the hydrogen atoms of NADH to certain organic molecules instead of the electron transport chain. This process is called fermentation. Bacteria have evolved dozens of different forms of fermentation, but eukaryotes primarily use two methods: ethanol fermentation and lactate (lactic acid) fermentation.
Glycolysis allows organisms to obtain energy from nutrients in the absence of oxygen. However, step 6 (See diagram) of the glycolytic pathway reduces NAD+ to NADH. Cells possess a limited supply of NAD+. If glycolysis continues without a mechanism to oxidize NADH back into NAD+, step 6 will be blocked and glycolysis will come to a halt. In oxidative respiration, the ETC oxidizes NADH to NAD+, allowing glycolysis to continue.
Organisms have evolved several ways of recycling NAD+ and allowing glycolysis to continue when oxygen is not available. One method involves transferring the hydrogen atoms of NADH to certain organic molecules instead of the electron transport chain. This process is called fermentation. Bacteria have evolved dozens of different forms of fermentation, but eukaryotes primarily use two methods: ethanol fermentation and lactate (lactic acid) fermentation.
Lactate (Lactic Acid) Fermentation
•Under normal conditions (optimum oxygen levels) humans/mammals use aerobic respiration
•During strenuous activity (shortage of oxygen)
–Muscle cells respire glucose faster than oxygen can be supplied
–Lactate (Lactic Acid) Fermentation begins
•Under normal conditions (optimum oxygen levels) humans/mammals use aerobic respiration
•During strenuous activity (shortage of oxygen)
–Muscle cells respire glucose faster than oxygen can be supplied
–Lactate (Lactic Acid) Fermentation begins
During the process of glycolysis a total of 4 ATP are produced. 2 ATP were used in steps 1 and 3 with a net production of 2 ATP and 2 NADH.
The remaining energy is trapped in 2 pyruvate molecules.
At this point under normal conditions the pyruvate molecules would continue on to pyruvate oxidation, the Krebs Cycle and the Electron Transport Chain (ETC).
When oxygen levels reach a minimum, (strenuous activity), oxygen is no longer there to act as the final electron acceptor in the electron transport chain. The limited number of NADH molecules present can't give up their H atoms to the ETC. This causes all of the remaining NAD+ to remain in NADH form causing glycolosis and Krebs to come to a halt.
This problem has been solved evolutionarily by converting the pyruvate molecules to Lactate which reduces the NADH to NAD+. The NAD+ can then go back into glycolysis to produce more pyruvate molecules....rinse....and repeat.
When oxygen levels reach a minimum, (strenuous activity), oxygen is no longer there to act as the final electron acceptor in the electron transport chain. The limited number of NADH molecules present can't give up their H atoms to the ETC. This causes all of the remaining NAD+ to remain in NADH form causing glycolosis and Krebs to come to a halt.
This problem has been solved evolutionarily by converting the pyruvate molecules to Lactate which reduces the NADH to NAD+. The NAD+ can then go back into glycolysis to produce more pyruvate molecules....rinse....and repeat.
Here is an animation of what happens when oxygen levels are below the minimum level.
Oxygen Debt Competition
The accumulation of lactate molecules in muscle tissue causes stiffness, soreness, and fatigue. Lactate is transported through the bloodstream from the muscles to the liver.
When vigorous exercise ceases, lactate is oxidized back to pyruvate, which then goes through the Krebs cycle and oxidative phosphorylation. The extra oxygen required to catabolize lactate to CO2 and H2O (through the aerobic pathway) is referred to as oxygen debt. Panting after bouts of strenuous exercise is the body’ s way of “paying” the oxygen debt.
To demonstrate the feeling of repaying the oxygen debt you can try this activity with the students.
Tell the students to:
1. Hold one hand up in the air
2. Exhale as much air out of their lungs as possible
3. Take a deep breath
4. Hold it for as long as you possibly can
5. Start a timer on the board to see how long you can hold your breath
6. When you have to take a breath, lower your hand
7. See who can hold their breath the longest
8. When the last student takes a breath walk the class through what they did and explain that the heavy breathing is your body repaying the oxygen debt.
The accumulation of lactate molecules in muscle tissue causes stiffness, soreness, and fatigue. Lactate is transported through the bloodstream from the muscles to the liver.
When vigorous exercise ceases, lactate is oxidized back to pyruvate, which then goes through the Krebs cycle and oxidative phosphorylation. The extra oxygen required to catabolize lactate to CO2 and H2O (through the aerobic pathway) is referred to as oxygen debt. Panting after bouts of strenuous exercise is the body’ s way of “paying” the oxygen debt.
To demonstrate the feeling of repaying the oxygen debt you can try this activity with the students.
Tell the students to:
1. Hold one hand up in the air
2. Exhale as much air out of their lungs as possible
3. Take a deep breath
4. Hold it for as long as you possibly can
5. Start a timer on the board to see how long you can hold your breath
6. When you have to take a breath, lower your hand
7. See who can hold their breath the longest
8. When the last student takes a breath walk the class through what they did and explain that the heavy breathing is your body repaying the oxygen debt.
STSE
You can relate lactic acid fermentation in the human body to how it effects athletes. To show how physical training can improve systems you can use the first part of the following RadioLab podcast. This podcast starts with an interview with Julie Moss who competed in the 4th Ironman competition. There is also a video of Julie struggling to complete the race. The STSE relation is that she had very little training and most of her systems shut down at the end of the race when she needed them most.
You can relate lactic acid fermentation in the human body to how it effects athletes. To show how physical training can improve systems you can use the first part of the following RadioLab podcast. This podcast starts with an interview with Julie Moss who competed in the 4th Ironman competition. There is also a video of Julie struggling to complete the race. The STSE relation is that she had very little training and most of her systems shut down at the end of the race when she needed them most.
Ethanol Fermentation
- A biological process that converts sugars (glucose, fructose, sucrose) into energy that can be used by the organism
- The waste products from this process are ethanol and carbon dioxide
During the process of glycolysis a total of 4 ATP are produced. 2 ATP were used in steps 1 and 3 with a net production of 2 ATP and 2 NADH.
The remaining energy is trapped in 2 pyruvate molecules.
When oxygen levels are either to low or non-existent to complete aerobic respiration the alternative pathway of ethanol fermentation begins.
The CO2 is removed from the pyruvate by the enzyme pyruvate decarboxylase.
This process forms 2 acetaldehyde.
The 2 NADH oxidizes to NAD+ by reducing 2 acetaldehyde to ethanol.
The NAD+ can then be used in glycolysis again.
The by-products CO2 & Ethanol are then removed as waste.
Humans have found numerous ways of using the waste products from ethanol fermentation.
Some of these include baked goods, beer, wine and soy sauce.
Activities and Labs
Clothespin Activity Lab
In this activity students will investigate cellular respiration, and the factors that affect
skeletal muscle fatigue.
In this activity students will investigate cellular respiration, and the factors that affect
skeletal muscle fatigue.
lab_-_clothespin.pdf | |
File Size: | 112 kb |
File Type: |
Metabolic Processes Lab
This lab was obtained from The Crucible online from STAO.
This lab features an investigation into the effect of oxygen on the rate of carbon dioxide production by yeast.
This lab was obtained from The Crucible online from STAO.
This lab features an investigation into the effect of oxygen on the rate of carbon dioxide production by yeast.
lab_-_co2_production_by_yeast.pdf | |
File Size: | 66 kb |
File Type: |
SmarterScience
Smarter Science is a framework for teaching and learning science in grades 1–12 and for developing the skills of inquiry, creativity, and innovation in a meaningful and engaging manner. Students engaged in Smarter Science-based activities are actively investigating and problem solving, enabled by a teacher who helps them address challenges relevant to their world. As they learn to think and act like scientists, students become increasingly independent and self-confident learners.
SmarterScience offers free downloads of all their posters at the following link: SmarterScience Posters
Smarter Science is a framework for teaching and learning science in grades 1–12 and for developing the skills of inquiry, creativity, and innovation in a meaningful and engaging manner. Students engaged in Smarter Science-based activities are actively investigating and problem solving, enabled by a teacher who helps them address challenges relevant to their world. As they learn to think and act like scientists, students become increasingly independent and self-confident learners.
SmarterScience offers free downloads of all their posters at the following link: SmarterScience Posters
Pictonary Countdown Consolidation Activity
This is a great activity to consolidate the lesson.
This is a great activity to consolidate the lesson.
- Assign students into groups of at least 4 people
- Have a designated drawer
- Tell each drawer that they need to come to you to find the first item on the list that needs to be drawn
- Once a group guesses the correct answer the drawer needs to come back to you and find out the next item on the list
- Repeat this until all groups have completed drawing and answering your list of curriculum related items