Figure 1 - Components of a typical animal cell. 1) Nucleolus 2) Nucleus 3) Ribosome (little dots) 4) Vesicle 5) Rough endoplasmic reticulum 6) Golgi apparatus 7) Cytoskeleton 8) Smooth endoplasmic reticulum 9) Mitochondrion 10) Vacuole 11) Cytosol (fluid that contains organelles, comprising the cytoplasm) 12) Lysosome 13) Centrosome 14) Cell membrane
Within the cell structure, the mitochondria (9) are of particular interest to this discussion. A typical cell can contain anywhere from a few to a couple of thousand of these organelles. Multiple mitochondrion are referred to as mitochondria.
Figure 2 - Components of a typical mitochondrion
The mitochondrion is typically between 0.75 and 3 µm in size. Its primary function is to generate adenosine triphospate (ATP), a cell's chemical energy source. Mitochondria are also responsible for signalling, cell growth (division) and cell death (apoptosis). The (3.11) Inner boundary membrane is where ATP is produced by an electron transport chain process.
Figure 3 - Electron transport chain
Figure 3 provides an expanded view of the inter-membrane layer where a complex sequence of redox reactions occurs. Above the layer you will find the inter-membrane space and below the matrix space.
Important concepts to note …
Overall, there is a continuous cycle between ATP and adenosine diphosphate (ADP) that can be expressed as.
ATP + H2O ↔ ADP + Pi
The energy released by the ATP → ADP reaction is used for various cellular activities.
The electron transport chain transforms ADP back to form a new ATP molecule.
Adult human turnover of ATP is anywhere from 75 to 150 kg per day!