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B8 Respiration and gas exchange - Coggle Diagram
B8 Respiration and gas exchange
Uses of energy in the body
Respiration is a chemical process that involves the breakdown of nutrient molecules (specifically glucose) in order to release the energy stored within the bonds of these molecules
Respiration can take place with oxygen (aerobically) or without oxygen (anaerobically). Much less energy is released for each glucose molecule broken down anaerobically compared to the energy released when it is broken down aerobically
Respiration occurs in all living cells. Most of the chemical reactions in aerobic respiration take place in the mitochondria
Humans need this energy to do the following things
Contract muscle
Synthesise proteins
Cell division (to make new cells)
Grow
Enable active transport to take place
Allow nerve impulses to be generated
Maintain a constant internal body temperature
Aerobic Respiration
Aerobic respiration requires oxygen and is defined as the chemical reactions in cells that use oxygen to break down nutrient molecules to release energy
It is the complete breakdown of glucose to release a relatively large amount of energy for use in cell processes
It produces carbon dioxide and water as well as releasing useful cellular energy
Glucose + Oxygen → Water + Carbon Dioxide + Energy
C6H12O6 + 6O2 → 6CO2 + 6H2O
Anaerobic respiration
Anaerobic respiration does not require oxygen and is defined as the chemical reactions in cells that break down nutrient molecules to release energy without using oxygen
It is the incomplete breakdown of glucose and releases a relatively small amount of energy for use in cell processes
It produces different breakdown products depending on the type of organism it is taking place in
You need to know the equations for anaerobic respiration in humans (animals) and the microorganism yeast
Anaerobic respiration mainly takes place in muscle cells during vigorous exercise
When we exercise vigorously, our muscles have a higher demand for energy than when we are resting or exercising normally. Our bodies can only deliver so much oxygen to our muscle cells for aerobic respiration
In this instance, as much glucose as possible is broken down with oxygen, and some glucose is broken down without it, producing lactic acid instead
There is still energy stored within the bonds of lactic acid molecules that the cell could use; for this reason, less energy is released when glucose is broken down anaerobically
Glucose → lactic acid
C6H12O6 →2C3H6O3
Lactic acid and oxygen debt
Lactic acid builds up in muscle cells and lowers the pH of the cells (making them more acidic)
This could denature the enzymes in cells so it needs to be removed
Cells excrete lactic acid into the blood. When blood passes through the liver, lactic acid is taken up into liver cells where it is oxidised, producing carbon dioxide and water (Lactic acid reacts with oxygen – this is actually aerobic respiration with lactic acid as the nutrient molecule instead of glucose)
So the waste products of lactic acid oxidation are carbon dioxide and water
This is the reason we continue to breath heavily and our heart rate remains high even after finishing exercise – we need to transport the lactic acid from our muscles to the liver, and continue getting larger amounts of oxygen into the blood to oxidise the lactic acid
This is known as ‘repaying the oxygen debt’
Comparison of aerobic and anaerobic respiration
Aerobic
needs oxygen
glucose breakdown is complete
produces carbon dioxide and water
releases a lot of enerrgy
Anaerobic
doesn't need oxygen
glucose breakdown is incomplete
animal cells produce lactic acid yeast produces carbon dioxide and ethanol
releases little energy