Question

Some help please?
Detailed descriptions of what happens to the carbon atom:
during photosynthesis (the light-dependent reactions and the light-independent reactions)
transitioning between photosynthesis and respiration
during cellular respiration or fermentation
An explanation of how the carbon atom is transferred between molecules. Please include descriptions of the molecules involved in each of the processes above and be sure to mention the movement of electrons and energy as the carbon atom moves from one reaction to another.

Answer 1

Here's a quick drawing of a general overview of what's going on with the carbon atom.

In green is the chloroplast, in blue is the mitochondrion. Purple is the cell membrane. Carbon atoms are turquoise. We'll follow the one specially marked light blue as an example of one possible path a carbon might take.

Let's start in the bottom right corner!

CO2 (blue carbon attached to two red oxygens) diffuses into the cell. It enters the chlroplast. A special enzyme (depicted as a golden triangle) called Rubisco catalyzes the carbon fixation reaction: the carbon dioxide is attached to a 5 carbon compound known as ribulose bisphosphate. This is step one of the Calvin Cycle. This reaction forms an unstable 6 carbon compound which quickly splits into two 3 carbon compounds. The energy frmo the light reactions, in the forms of ATP and NADPH, is stored into these three carbon compounds. Per every 3 carbon atoms, one 3 carbon compound exits this cycle into the cytoplasm. Through a set of reactions, this 3 carbon compound (aaka glyceraldehyde 3 phosphate) is transformed into a glucose molecule. Glucose then can be stored or used for other activities, but in our case, we'll shuttle it back into cellular respiration.

As you know, the first step is glycolysis. The specific reactions of glycolysis are beyond the scope of my drawing abilities; you can find them anywhere online though. At the end of glycolysis, you're left with two pyruvate molecules. Pyruvate (3 carbons) enters the mitochondrion, becoming acetyl co-A (2 carbons) in the process.

Here begins the Krebs Cycle. Acetyl Co-A combines with oxaloacetate (thhe 4 carbon compound) to form citrate (the 6 carbon compound). The 6 carbon compound is broken down to a 4 carbon compound, in each step releasing a carbon dioxide molecule. Here is where our original carbon, fixed back in the chlroplast, can be released. Oh and - the four carbon compound in the Krebs cycle continues to lose energy to NADH and FADH2, which carry it over to the electron transport chain (yellow arrows) which ultimately generates ATP.

Hope this helps! Unfortunately I do not have the time to go into the specifics of the reactions. I also want to point out that I basically skipped over the light reactions and the electron transport chain - this is because carbon is not directly involved.

Answer 2

@yayanieves

Answer 3

@alphadxg

How did I do? (=

Answer 4

That was an amazing explanation. Biology Rocks!

Answer 5

Thanks so much!!! Sorry I took so long to see this! You absolutely rock!!!! @Popraci

Answer 6

@yayanieves

Thanx For The Metal's and It Was A Pleasure Help You With This Question. Please let Me Know If You Need Any Other Help.

Answer 7

No problem!! You were a big help! And if I need anymore biology help I'll be sure to come to you :) @Popraci