living organisms require energy to function and this includes each and every one of the trillions of cells that constitute the human body. Define in detail and use diagrams appropriate to show how cells extract, use and store energy including but to limited to discussion of cell respiration, glucose, pyruvic acid, glycolysis, krebs cycle, atp, nadh and fadh and electron transport. how much by the complete breakdown of glucose? why is breathing necessary for cellular respiration in animals?

To understand how cells extract, use, and store energy, let's break it down step by step, starting with the process of cell respiration. I'll use diagrams to illustrate the key processes involved.

1. Cell Respiration:
Cell respiration is the process through which cells convert the energy stored in nutrients, such as glucose, into a usable form called adenosine triphosphate (ATP). ATP is the energy currency of cells, responsible for powering various cellular activities.

Diagram 1:
```
+---+ +---+
|Glucose + Oxygen --> Carbon | ATP |
| Dioxide | |
+---+ +---+
```
In the above diagram, glucose (a sugar molecule) is combined with oxygen through cell respiration to produce carbon dioxide and ATP.

2. Glucose Metabolism:
To extract energy from glucose, cells go through several stages: glycolysis, pyruvic acid conversion, Krebs cycle, and electron transport chain.

Diagram 2:
```
+---------+
| Glucose |
+----+----+
|
v
+----+---+ +------+ +-------------+
| Glycolysis | --(pyruvic ->| Krebs |---(NADH+ | Electron |
| | acid+NADH) | Cycle | FADH2) | Transport |
+----+---+ +------+ +-------------+
|
v
+----+----+
| ATP |
+----------+
```
In this diagram, glucose is first converted into two molecules of pyruvic acid through glycolysis. This process yields a small amount of ATP and NADH (which carries high-energy electrons). Pyruvic acid then enters the next stage, the Krebs cycle, which further produces NADH and FADH2 (another electron carrier). Finally, these electron carriers feed into the electron transport chain, generating ATP.

3. ATP Production:
During the stages of glucose metabolism, ATP is produced through a process called oxidative phosphorylation, which occurs in the mitochondria.

Diagram 3:
```
+------+ +--------+
| NADH | + 3H+ + 1/2O2 -> | NAD+ |
| | | |
+------+ +--------+
| |
v v
+----+ +----------+
| FADH2| + 1/2O2 + 2H+ -> |FAD + 3H2O|
| | | |
+----+ +----------+
| |
v v
+----+ +----+
|ATP | | ADP |
| | | |
+----+ +----+
```
In this diagram, NADH and FADH2 from the previous steps donate their electrons to create a flow of electrons (electron transport chain). This flow of electrons moves through protein complexes, driving the production of ATP. Oxygen (O2) acts as the final electron acceptor, combining with hydrogen ions (H+) to form water (H2O).

The complete breakdown of glucose generates a total of 38 molecules of ATP through cell respiration.

Breathing (the exchange of oxygen and carbon dioxide) is necessary for cellular respiration in animals because oxygen is the final electron acceptor in the electron transport chain. The oxygen we breathe in is transported by the respiratory system to the cells, where it combines with hydrogen ions and electrons to produce water. Without oxygen, the electron transport chain cannot proceed, leading to a lack of ATP production. This is why animals require a continuous supply of oxygen through breathing to sustain cellular respiration and energy production.