5.3 METABOLISM: THE CHEMISTRY OF LIFE
What are the basic metabolic needs of life?
These processes, which are all chemical in nature, make up what we call metabolism.
Without the help provided by the cell itself, the reactions would occur too slowly to be useful for life.
A cell’s primary purpose is to serve as a tiny chemical factory in which desired chemical reactions occur much more rapidly than they could otherwise。
This way, simple molecules can finally turn into the great variety of complex organic molecules needed by living organisms.
This biochemical manufacturing process requires two basic things:
1. A source of raw materials with which to build new products. In the case of living cells, the key raw materials are molecules that provide the cell with carbon
and other basic elements of life.
2. A source of energy to fuel the metabolic processes that break down old molecules and manufacture new ones.
Not that much raw material is needed, because cells can build a incredible variety of materials from a limited set of raw materials because they have enzymes.
The reason cells can produce so much variety is because they put energy to work in the same way, using the ATP.
ATP stands for adenosine triphosphate, and it stores and release energy for all the chemical manufacturing.
A cell needs outside energy to produce ATP, and then the ATP can provide energy for the cell.
ATP is recyclable, so if a cell draws energy from ATP, it leaves byproduct called ADP that can be turned back into ATP.
ADP stands for adenosine diphosphate.
Every life on earth uses ATP for energy storage is another evidence that there is a common origin to life.
We fuel the ATP in our cells with food, others go through chemical reactions and sunlight. Photo means light and chemo means chemicals.
Heterotroph means eating and autotroph means environmental carbon dioxide.