UNIT 12: RESPIRATION
Respiration is a chemical process where glucose is broken down to release energy to
carry out different cellular processes
This reaction happens in almost all of the cells in the body
The process of respiration is controlled by enzymes
Breathing is the physical process of inhaling oxygen and exhaling carbon dioxide in
and out of the lungs. However, respiration is the chemical process which releases
energy from glucose
USES OF ENERGY
The uses of energy in living organisms include:
o Muscles contraction
o Protein synthesis
o Cell division
o Active transport
o Growth
o Passage of nerve impulses
o Maintenance of a constant body temperature
EFFECT OF TEMPERATURE ON RESPIRATION
Yeast is a living organism so it can be used to determine of temperature affects
respiration. This is done by the following steps:
1.) Add yeast and glucose solution to a test tube
2.) Place the test tube in a water bath of 30 degrees Celsius
3.) Add a drop of methylene blue to the test tube and start the timer. Shake
for 10 seconds
4.) Record how long it takes for methylene blue to turn colourless
5.) The faster the solution turns colourless, the faster the rate of respiration
6.) Repeat the experiment at different temperatures
7.) Find the rate of respiration at each temperature
The amount of variables that must be controlled in the experiment above are:
o Amount of methylene blue dye added
o Amount of yeast suspension in the test tubes
o Concentration of glucose
o pH
The time taken for colour change can be converted into rate of respiration by using
the formula 1
Time
The optimum temperature is 40 degrees Celsius
On the graph, the rate of respiration increases as the temperature increases in a
curved line and it will be at its peak in 40 degrees Celsius and the rate of respiration
will start to decrease after 40
AEROBIC RESPIRATION
Respiration can be taken place in two different ways
o Aerobically – With oxygen
o Anaerobically – Without oxygen
Aerobic respiration is the chemical reaction in cells that use oxygen to break down
nutrient molecules to release energy
The word equation for aerobic respiration is:
Glucose + oxygen Carbon dioxide + water + Energy
The balanced chemical equation for aerobic respiration is:
C6H12O6 + 602 6CO2 + 6H20
ANAEROBIC RESPIRATION
Anaerobic respiration is the chemical reactions is cells that break down nutrient
molecules to release energy without using oxygen
Anaerobic respiration releases much less energy per glucose molecule that aerobic
respiration
ANAEROBIC RESPIRATION IN YEAST
Anaerobic respiration in yeast is used for bread making and brewing
The word equation for anaerobic respiration of yeast is:
Glucose Alcohol + Carbon dioxide + Energy
The balanced chemical equation for anaerobic respiration of yeast is:
C6H12O6 2C2H5OH + 2CO2
ANAEROBIC RESPIRATION IN ANIMALS
Anaerobic respiration also takes place in muscle cells during rigorous exercise
The word equation for anaerobic respiration in muscles during rigorous exercise is:
Glucose Lactic acid + Energy
When we do rigorous exercise, our muscles demand more energy. The energy
needed cannot be provided by just aerobic respiration because muscle cells may not
be receiving oxygen quick enough. Therefore, anaerobic respiration must take place
to provide the necessary energy
This breaks down glucose without oxygen which produces lactic acid as a toxic waste
product
Less energy is produced when glucose is broken down anaerobically
Lactic acid builds up in the muscle cells and this can prove to be toxic to muscles so it
needs to be removed
Even after exercise, the heart rate continues to be fast so that it can transport lactic
acid in the blood from the muscles to the liver quickly
At the liver, the lactic acid reacts with oxygen and produces carbon dioxide and water
This is actually aerobic respiration, with lactic acid as the nutrient molecule instead
of glucose
The temporary shortage of oxygen during vigorous exercise is known as oxygen debt
Even after exercise, we continue to breathe deeper and faster in order to supply
enough oxygen for lactic acid to break down into water and carbon dioxide, to repay
the oxygen debt
