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Wednesday, 9 May 2012


2.33 recall that the process of respiration releases energy in living organisms

Just recall this. Energy is locked up in food molecules such as glucose. Living organisms release energy by breaking these molecules down. Without respiration, you wouldn’t have energy to do all your physical activities and survive. 
Plants and most animals, including humans, respire aerobically. These complex organisms need a lot of energy to survive. Some examples of energy-consuming processes in organisms are:

  • The synthesis of proteins from amino acids
  • Cell division
  • Muscular contractions such as heartbeats and respiratory movements
  • Active transport in the absorption of food substances by the small intestine
  • Transmission of nerve impulses or messages

2.34 describe the differences between aerobic and anaerobic respiration

Aerobic respiration is with oxygen, anaerobic respiration is without. Basically, your muscle cells can respire anaerobically for short periods of time when there is a shortage of oxygen.

Aerobic respiration is actually a multi-step reaction that is catalysed by enzymes in the mitochondria. 

And aerobic respiration releases more energy, but the good thing with anaerobic respiration is that it’s almost instant, it’s quick-which is why events such as a 100m sprint  which requires a quick burst of energy is anaerobic.

But anaerobic respiration leads to the production of lactic acid-a poison, which builds up in your muscles. The lactic acid concentrations build up slowly in the muscles and may eventually become high enough to cause fatigue, muscular pains and cramps to stop you from continuing.

This is why you continue to breathe hard after anaerobic exercise for a while, as you are repaying your oxygen debt, which is the oxygen required to oxidize and convert the harmful lactic acid into harmless products like carbon dioxide and water.

2.35 recall the word equation and the balanced chemical symbol equation for aerobic respiration in living organisms

Glucose + oxygen à carbon dioxide + water + energy (ATP)
My class likes to use ‘ATP’ in place of energy, and it stands for adenosine triphosphate. It's like the 'currency' of energy. I'll let this link do the explaining of what it is:
The explanation in the link may be confusing, as we don't need that kind of depth yet. In very basic terms, ATP is like small packets of energy. They store energy temporarily and provide energy for all the reactions taking place in the cell.

C6H12O6 + 6O2 à 6CO2 + 6H2O + ATP

2.36 recall the word equation for anaerobic respiration in plants and in animals

Glucose à lactic acid + ATP (smaller amount!)

C6H12O6 à 2C3H6O3 + ATP

The small amount of energy released in anaerobic respiration, together with that produced in aerobic respiration, is sufficient to keep the muscles contracting.
Keep in mind that this equation is different for alcoholic fermentation where yeast respires anaerobically. This is used in the production of bread to make bread rise, as the carbon dioxide produced raises the bread.
Glucose à ethanol + carbon dioxide + small amount of energy
Note that the glucose molecule is only partially broken down in anaerobic respiration. The ethanol produced still contains much energy, hence explaining why only a small amount of energy is set free in anaerobic respiration. 

As you can see, anaerobic respiration and removing lactic acid is much more complex than what I've described, but you don't need to concern yourself with glycolysis for now. Just know the equations I've stated above and all the general stuff. :)


  1. Thanks! Helpful!

  2. Helped me with my GCSE preparation. Thanks!

  3. So useful, this helped me in my test sooo much. Many thanks!!


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