Photosynthesis/Cell Respiration

Kambree Ellison


Photosynthesis in a nutshell is this: plants use the sun and water for energy which does some magic and produces oxygen and carbohydrates as byproducts. To understand it deeper though, you have to dig a little farther.

There are two phases in which photosynthesis occurs, one is the light reactions (light dependent) and the other is dark reactions (light independent). Basically this means that phase one depends on the sun for it to occur, but for the dark reactions it does not need sunlight because it is independent.

Then phase one is split into two parts, stage one and stage two.

The sun does what it does best and shines down on the plant, the photons (sound anything like photosynthesis?) excites the chloroplast and makes it shoot across the electron chain. When it's shot across the electron chain it makes all the other electrons become excited as well, this is the first stage.

During this process, water molecules split which makes oxygen and hydrogen ions be released into the atmosphere, viola the air you and I breathe today. The electron chain uses and creates ATP, then makes NADPH, both which will be for the next stage.

So moving out of the light reactions, in the dark reactions there is only one stage. This stage is a cycle named the Calvin Cycle. In the Calvin Cycle a one carbon atom, that is taken from the atmosphere in the molecule CO2, is added to a five carbon sugar. Once the six carbon is formed it splits into two molecules of three carbon atoms. The molecules use the ATP and NADPH from before to form more ATP and NADPH. One of the atoms goes off to become glucose, making two carbon sugars and three carbon sugars. These molecules collide forming a five carbon sugar, starting all over again.

There you have it; photosynthesis.

Cellular Respiration

Cellular Respiration has a few stages itself. It starts off with glycolysis, which can determine whether the pyruvate goes to the mitochondria or to fermentation, then depending on if it went to the mitochondria it goes to the Kreb's Cycle, lastly the electron transport chain.

The first stage, glycolysis, is when glucose is broken down and formed into pyruvate acid. The beginning starts off with your typical C6H12O6 (glucose), than with the little help of 2ATPs it splits the carbon atoms into two three compounded structures. The compounded structures have an added phosphate (PGAL). NAD+ goes in and out comes NADH, causing two pyruvate atoms to attach. Two more ATPs are used to produce pyruvate acid. If there is oxygen it goes to the mitochondria, but if it doesn't have oxygen it will under go fermentation. In the mitochondria it loses it's CO2 and NADH, leaving us with CH3-C-S.

After all of this stage two, the Kreb's Cycle. In the Kreb's Cycle a four carbon sugar is added, than CoA it lost, now there is a six carbon sugar. CO2 and NADP leave, making it a five carbon sugar. After that CO2 and 2NADH and ATP escape, leaving it to only a four carbon sugar. FADH2 and NADH leave, and finally the cycle starts all over again.

The last stage is the electron transport chain. this is where the NADH enters the electron, causing H+ to leave the electrons. ADP and Pi enter and ATP exit, the end of Cell Respiration.


These processes are alike, in a way that they are opposites. Now that doesn't make the best sense, but what I'm saying is photosynthesis intakes carbon dioxide, and produces oxygen. In cellular respiration, it intakes oxygen and creates carbon dioxide.

Both technically make energy (ATP) in order to function and both have an electron transport chain involved.

In photosynthesis sunlight is needed, but in cellular respiration light isn't needed. Photosynthesis creates ATP and cellular respiration uses ATP. There are many differences and similarities, but the main thing is that they depend on each other to survive.