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1/10/11

Cellular Respiration and Photosynthesis - The BIG Picture

Most likely on your finals your teachers will ask you to compare photosynthesis and cellular respiration. How DO they compare??

First write out their chemical formulas:

Cellular Respiration: C6H12O6 (glucose)+6O2 --> 6H20+6CO2+ATP
We breath in Oxygen and break down glucose (a sugar monomer) to provide our cells with energy in the form of ATP while breathing out Carbon Dioxide as a byproduct 

Photosynthesis: 6CO2+6H20+Sunlight --> C6H1206(glucose)+6O2
Plants take in Carbon Dioxide and use sunlight to convert six of them into a glucose molecule, giving off oxygen as a byproduct  

Do you see how the reactants (the left side of the equation) of one formula is pretty close to the products (the right side of the equation) of the other formula?  

Cellular Respiration and Photosynthesis are opposite chemical reactions! 

Now lets compare these two in several contexts.. 

In terms of the atmosphere...
- Photosynthesis INCREASES Oxygen concentration and DECREASES Carbon Dioxide concentration
- Cellular Respiration DECREASES Oxygen concentration and INCREASES Carbon Dioxide concentration 

In terms of an Anabolic or Catabolic reaction..
(An Anabolic reaction is a chemical reactions that BUILDS UP a molecule, where as a Catabolic reaction is a chemical reaction that BREAKS DOWN a molecule)
- Photosynthesis is a Anabolic reaction (builds a glucose molecule)
- Cellular Respiration is a Catabolic reaction (breaks down a glucose molecule to make ATP)

In terms of an Endothermic or Exothermic reaction..
(An Endothermic reaction requires energy to occur, where as an Exothermic reaction gives off energy)
-Photosynthesis is an Endothermic reaction as it requires energy from sunlight to occur
-Cellular Respiration is an Exothermic reaction as the product is ATP (energy)

By writing the chemical formula for both these reactions at the top of your paper, the answer for these questions will be right there! Keep referring back to them to look and see what molecules remain on the "reactants" side and the "products" side. 


Now here's a question for ya..

Ancient earth had very low levels of Oxygen in the atmosphere but very high levels of Carbon Dioxide. How do you think Oxygen concentration increased so lifeforms like humans could live on earth??

4 comments:

  1. The oxygen concentrations on Earth steadily increased as the population od plants increased and evolveddue to the presence of water.

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  2. Overall plants release decrease the amount of carbon dioxide and increase the oxygen levels :)

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  3. sorry the *release was not meant to be there

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  4. The oxygen levels increased due to the plants living for anlong time before humans were every on the planet. Once the human species evolved and required oxygen, there was enough for them to survive and keep on surviving.

    ReplyDelete