Production of oxygen during photosynthesis

Question

Production of oxygen during photosynthesis

is a direct result of the electron transport chain.

is the byproduct of the breakdown of water.

is the primary goal of photosynthesis.

occurs during the light-independent reactions.

Answer 1

is the byproduct of the breakdown of water.

Plants can do two important things:

Use energy from the sun to turn CO₂ (carbon dioxide) and H₂O (water) into sugar (C₆H₁₂O₆) with oxygen (O₂) left over. This is photosynthesis.

And they can:

Break down the sugar (C₆H₁₂O₆) into CO₂ (carbon dioxide) and H₂O (water), but they need (O₂) oxygen to do it. This is cellular respiration.

We can only do the second thing.

The first law of thermodynamics tells us that matter cannot be created or destroyed. It cannot come from nothing and it cannot disappear. So the same number of atoms (C, H, O) have to enter and leave. Let us write photosynthesis as a balanced equation.

Photosynthesis:

6CO₂ + 6H₂O gives C₆H₁₂O₆ + 6O₂

Count up the number of carbon atoms on each side of the arrow. If you have six on one side, you need six on the other. Now count the hydrogen atoms. (6 X 2) on one side and 12 on the other. How many oxygen atoms are on the left side?

(6 X 2) + (6 X 1) = ___. Now how many oxygen atoms are in the glucose? 6.

So you have oxygen atoms left over. That is where the O₂ comes from. It is the left over material from making sugar. Just like when you make something, the scraps you cut off do not disappear. The plant breathes out the oxygen, which is good for all of us animals because we need oxygen, as you know.