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[h] iGCSE Biology Notes Respiration
[q] Uses of energy in the body
[a]
■ Maintenance of a constant body temperature
■ Passage of nerve impulses
■ Cell division and growth
■ Muscle contractions
■ Protein synthesis
■ Active transport
[q] Energy is produced by respiration
[a]
■ Respiration is a series of reactions that are controlled by enzymes.
■ Can take place without or without oxygen
[q] Aerobic respiration
[a]
○ Aerobic respiration requires oxygen and is defined as the chemical reaction in cells that use oxygen to break down nutrient molecules to release energy
○ It is the complete breakdown of glucose to release large amount of energy for use in cell processes
○ It produces carbon dioxide and water as well as releasing useful cellular energy
○ C6H12O6 + 6O → 6CO2 + 6H2O
○ Glucose + Oxygen => carbon dioxide + water
[q] Investigating uptake of oxygen by respiring organisms
We can investigate aerobic respiration in living organisms by measuring the amount of oxygen that they take from the air
[a]
■ Done by finding the change in volume
■ Carbon dioxide has to be removed at the as it is being produced by the respiring organism
● Done by adding soda lime or sodium hydroxide
[q] Investigating uptake of oxygen by respiring organisms
We use a respirometer to do this (image on next page)
[a]
■ Two tubes, one with an organism and another with beads of same mass as the organism as control
■ The movement of the colored liquid towards the insect will give a measure of the volume of oxygen taken up by the insect for respiration
■ The reduction of volume in the tube increases pressure causing the coloured liquid to move
■ The distance moved by the liquid will provide the volume of oxygen in by the insect per minute
[q] Investigating uptake of oxygen by respiring organisms
[a]
[q] To investigate the effect of temperature on seeds
[a]
○ Heat the side containing the seed at different temperatures and measure the distance moved
○ The seeds should be kept in the water bath for 15 minutes before the start off the experiment to ensure they have acclimated to the temperature
○ respiration is an enzymes controlled reaction.
■ So the enzyme will denature after 40 °C
[q] Anaerobic Respiration
[a]
○ Does not require oxygen
○ Defined as the chemical reactions in cells that break down molecules to release energy without using oxygen
○ Less energy produced per glucose molecule than in aerobic respiration
○ It produces different breakdown products depending on the type of organism it is taking place in .
■ Respiration in Yeast
● Glucose => Alcohol + carbon dioxide
● C6H12O6 => 2C2H5OH + 2CO2
■ Glucose => Lactic acid
■ Anaerobic respiration takes place in muscle cells during vigorous exercise
● Lactic acid builds up in muscles and blood during vigorous exercise causing an oxygen debt
■ Recovery of Oxygen debt
● Aerobic respiration of lactic acid in the liver
○ This causes a fast heart rate even after exercise is over
● Transports lactic in blood from muscles to the liver
● Deeper breathing, supplying oxygen for aerobic respiration of lactic acid
[q] Respiration In animals
[a]
■ Glucose => Lactic acid
■ Anaerobic respiration takes place in muscle cells during vigorous exercise
● Lactic acid builds up in muscles and blood during vigorous exercise causing an oxygen debt
■ Recovery of Oxygen debt
● Aerobic respiration of lactic acid in the liver
○ This causes a fast heart rate even after exercise is over
● Transports lactic in blood from muscles to the liver
● Deeper breathing, supplying oxygen for aerobic respiration of lactic acid
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