Question

Algae are oxygenic photosynthetic organisms (that use photosystems I & II as discussed in class). (A) At minimum, how many photons are needed before an algae cell can replicate (i.e. split into two cells), assuming that an algae cell contains 1011 carbon atoms? (B) Explain your answer. please only respond if you for sure know the answer, thank you!!

Answer 1

This is about calculating how many photons are required to produce enough energy to fix one CO2 molecule. Then multiply it by the 1011 carbons that an algae cell have.

Let's start by the ending and then track back until reaching photons:

Carbon fixation is the ending, and carbon is fixed into carbohydrate molecules, to actually produce glucose. How many ATP molecules are needed to produce one glucose molecule? 18 ATPs (and 12 NADPH)

Now, where is ATP produced? in the light dependant reactions. 2 water molecules need to be cleaved to produce enough high energy electrons to finally produce 4 ATP molecules. We need 8 photons to reach enough energy to cleave those 2 water molecules. So let's start calculations to reach the number of photons for one algae cell division:

Now, let's put it in your A and B items:

A)

The algae needs to recieve at least 6,066 photons to be able to replicate.

B) This is about calculating how many photons are required to produce enough energy to fix one CO2 molecule. Then multiply it by the 1011 carbons that an algae cell have.

Let's start by the ending and then track back until reaching photons:

Carbon fixation is the ending, and carbon is fixed into carbohydrate molecules, to actually produce glucose. How many ATP molecules are needed to produce one glucose molecule? 18 ATPs

Now, where is ATP produced? in the light dependant reactions. 2 water molecules need to be cleaved to produce enough high energy electrons to finally produce 4 ATP molecules. We need 8 photons to reach enough energy to cleave those 2 water molecules. If we put all those equivalences we end up calculating the number of photons needed to create a new algae cell.