Respiration - Biology Form 2
By the end of this lesson you should be able to:
- Explain the importance of respiration.
- Identify two types of respiration in living organisms.
- Compare aerobic and anaerobic respiration.
- Explain the importance of anaerobic respiration in industry and at home.
- Describe experiments to show respiration in plants and animals.
Respiration is the process whereby food materials are broken down within the cell to release energy necessary for body activities.
In this topic you will learn more on how glucose is broken down to release energy for the cell.
In Form One respiration was identified as one characteristic of living organisms. In the topic of cell structures and function you learnt that the mitochondrion is the site for respiration. In the topic gaseous exchange we learn that oxygen and carbon IV oxide are the respiratory gases. In the topic nutrition we learnt that glucose is assimilated and broken down to release energy for the cell, we also learnt important factors that determine energy requirements in man.
In this topic on respiration we will learn more on how glucose is broken down to release energy for the cell.
Importance of Respiration
Respiration produces energy that is used to carry out various activities in the body. The activities include;
- Growth and development
- Repair of worn out tissues
- Muscle contractions to bring about various movements.
The pictures next show people in various activities requiring energy. Which of these people do you think is using more energy?
Patients in hospital
Learners in class
Types of respiration
During glycolysis, glucose molecules are broken down by enzymes into pyruvic acid with release of two ATP molecules for every glucose molecule. This occurs in the cell cytoplasmKREBS CYCLE
The pyruvic acid in the cytoplasm enters the mitochondrion. In presence of oxygen it becomes oxidized into carbon IV oxide and water. 36 ATP molecules are produced.
The overall reaction for aerobic respiration is shown.
Oxygen + glucose ------------> water + carbon IV oxide + energy.
Anaerobic respiration refers to the chemical breakdown of glucose in the absence of oxygen to liberate energy. Various organisms produce different products during the process.Anaerobic Respiration in Animals
In animals glucose is broken down anaerobically when oxygen supply is less than oxygen demand. Lactic acid is a toxic substance and must be quickly cleared from the respiring tissues. When oxygen is available the lactic acid is broken down into carbon IV oxide, ATP, and water. This is called paying of oxyen debt. The liver may also convert the lactic acid into glycogen for storage.
The picture shows sportsmen playing. Lactic acid is produced in muscles during such streneous activities due to inadequate supply of oxygen.
In the sportsmen the lactic acids will be broken down after the activity when the sportsman continues to breath in deeply. Deep and rapid breathing(panting) enables the sportsman to take in enough oxygen to break down the pyruvic acid. This is called paying the oxygen debt.
Anaerobic respiration refers to the chemical breakdown of glucose in the absence of oxygen to liberate energy. Various organisms produce different products during the process.Anaerobic respiration in animals
In animal cells glucose is usually broken down anaerobically during strenuous activities (when oxygen supply is less than oxygen demand). Two ATP molecules and lactic acid are produced. Lactic acid is a toxic substance and must be quickly cleared from the respiring tissues. When oxygen is available (paying of oxygen debt) the lactic acid is broken down in the respiring tissues into carbon IV oxide, ATP, and water. The liver may also convert the lactic acid into glycogen for storage.
Anaerobic respiration in Plants
In plants glucose is broken down in absence of oxygen into carbon IV oxide, ethanol and 2 ATP molecules of energy. This is called fermentation. Some fungus such as yeast can carry out fermentation.
The experiment shown in the video is a demonstration of fermentation.
In this experiment water is boiled to drive off any dissolved air.A small amount of sugar is dissolved in the water. This serves as a source of food for yeast. The water is allowed to cool. Yeast is then added. Cooling avoids denaturing the yeast.On cooling yeast is added and stirred with a glass rod. Liquid paraffin is added by tricking it gently down the side of the tube using a pipette. This prevents air from dissolving into the solution.An identical piece of apparatus is set up but use boiled yeast instead of living yeast. This serves as a control experiment. The apparatus is then left in a warm place for half an hour and observation made.The hydrogen carbonate indicator, lime water forms a white precipitate.
Glucose is anaerobically broken down to produce carbon IV oxide, ethanol and energy. Carbon IV oxide gas escapes and bubbles in the lime water making it form a white precipitate. It can be concluded that Carbon IV oxide is produced during anaerobic respiration in plants.
Note that in the demonstration with unboiled peas the thermometer shows increase in temperature while the boiled seeds does not show increase in temperature.
Seeds store food which is broken down during germination to produce energy in form of heat causing a rise in temperature. In the control set up, boiling denatured the enzymes in the seeds. The boiled seeds did not respire and therefore there was no rise in temperature.
Production of Heat during Respiration
Demonstration to show that heat is produced during germination.
In this experiment some seeds are soaked in water for a day so that they begin to germinate. A second set of beans is boiled to kill them. This is to be used in the control set up. Both sets of peas are then washed in dilute disinfectant, so that the bacteria and fungus are killed.Each set of beans is then put into a vacuum flask. The temperature of each flask is noted and recorded every day for four days.Observations
Note that in the demonstration with unboiled peas the thermometer shows increase in temperature while the boiled seeds does not show increase in temperature. Seeds store food which is broken down during germination to produce energy in form of heat causing a rise in temperature.In the control set up, boiling denatured the enzymes in the seeds. The boiled seeds did not respire and therefore there was no rise in temperature.
This experiment shows that during respiration energy is released.
Comparison between Aerobic and Anaerobic Respiration
As observed during the previous lessons in respiration there are clear differences and similarities between aerobic and anaerobic respiration.
Aerobic respiration is oxygen dependent. It only occurs in the presence of oxygen. It takes place in the cytoplasm and mitochondria. During this process glucose is completely broken down into carbon IV oxide and water. Aerobic respiration releases more energy. 38 ATP molecules are released from every molecule of glucose used.
Anaerobic respiration occurs in cell cytoplasm only. During this process glucose is partially broken down. The products are lactic acid and energy in animals. Plants release ethanol. Carbon IV oxide and energy. Less energy is released; only 2 ATP molecules for every sugar molecule used.
In both aerobic and anaerobic respiration glucose is broken down and energy is produced in form of ATP.
Application of Anaerobic Respiration in Industry and at Home
Baking industry; in this picture yeast is being used to break down sugars in the dough anaerobic ally to produce carbon IV oxide which causes the dough to rise. The same principle is applied in our homes as we make mandazi/mahamuti.
Dairy industry; in this pictures bacteria of different types are used to ferment milk to obtain a variety of milk products such as butter, cheese, gees and yoghurt.
Brewing industries; we can see the picture of a brewing industry and some alcoholic products of the industry. When fruits are fermented we obtain wine and when cereals are fermented we get beer. When wine or beer is fermented we obtain spirits.
Tea factory; the principle of fermentation is applied in making tea beverage.
Silage production; Silage is fodder preserved and stored by farmers to provide nutritious food stuff for livestock during dry weather. Silage making is done in silos. It depends on controlled fermentation of the green foliage in the silos.
Compost manure. The preparation of compost manure involves anaerobic respiration.
Biogas production. This is fermentation of domestic waste in air tight pits for the purpose of collecting methane gas as an alternative source of energy.
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