Respiration – cont’d
STUDENTS, ARE you feeling on top of the world? No? Why not? You are young, strong, bright, and the world is waiting for you to conquer, so why not? Come on now, smile and decide that if you do not have something kind to say to someone, you will not open your mouth!
We have spoken about respiration and familiarised ourselves with the two types of respiration: aerobic and anaerobic. This week, we continue with our study of anaerobic respiration. Remember that in anaerobic respiration, the end products are different depending on whether the organism is a plant or an animal.
Aerobic as well as anaerobic respiration occurs during strenuous exercise. Lactic acid is produced in anaerobic respiration and it cannot be used by the body, so it builds up in the muscles. This build-up causes the muscles to ache due to muscle fatigue; lactic acid is toxic to the muscles.
This form of respiration occurs when the amount of energy being produced by aerobic respiration is not enough to supply the muscles with sufficient energy to enable them to contract and relax at the rate required for the body to perform. After exercise, the muscles have to get rid of the lactic acid quickly because, as said previously, its presence is toxic and will cause fatigue. Removal is facilitated by the rapid intake of air. Have you ever wondered why you have to breathe so hard and fast after you have finished running? The air which is taken in, as a result of the hard breathing, provides the body with sufficient oxygen which can be used to convert the lactic acid from anaerobic respiration to carbon dioxide and water. The oxygen which is used to convert and remove the lactic acid is known as the ‘oxygen debt’.
Oxygen debt is the amount of oxygen required to convert the lactic acid from anaerobic respiration to carbon dioxide and water, thus removing it from the muscle cells.
IMPORTANCE OF ANAEROBIC RESPIRATION IN PLANTS
Do you remember the end products of anaerobic respiration in plants? Of course, you do! The end products are carbon dioxide and ethanol, along with energy. Be reminded of the equation:
The process is called fermentation and the importance of this process is listed below.
1. Bread making – Yeast dissolved in sugar solution is added to flour. The yeast respires anaerobically to produce carbon dioxide, which causes the dough to rise. The ethanol evaporates in the oven and, hence, cannot be tasted in the bread or biscuit.
2. Alcohol production – Fermentation is the process used to make beer, rum and wine (alcoholic beverages). The difference in the type of alcoholic beverage depends on the origin of the sugars being fermented. The alcohol that is formed becomes toxic to the yeast when it rises above 14%, and this stops the process.
3. Biogas production – This is produced from organic matter into which bacteria have been introduced. The bacteria respire anaerobically, decaying the organic matter to produce methane (biogas). The methane that is produced can be used as a fuel.
EXPERIMENT TO DEMONSTRATE ANAEROBIC RESPIRATION IN YEAST
Look at the experimental set-up and think about the following:
Why was the sugar boiled?
Why is there liquid paraffin on top of the yeast and sugar solution?
Why is lime water/hydrogen carbonate indicator in the outlet test tube?
A COMPARISON OF AEROBIC AND ANAEROBIC RESPIRATION ANSWERS TO QUESTIONS
Were you able to answer the questions? These are questions that you could be asked in the future so pay attention!
1. The sugar was boiled to remove/drive off all the air containing oxygen that was incorporated when the solution was being mixed.
2. The liquid paraffin prevents air from re-entering the mixture.
3. The lime water and hydrogen carbonate are carbon dioxide indicators. These liquids change colour when carbon dioxide mixes with them. This indicates that the reaction produced carbon dioxide.
See you all next week!