Early Life, Page 1: [Previous Page] [Next Page] [Syllabus] Textbook pages 71 - 79

Energy to Power Life

Life needs energy! Energy is needed to synthesize molecules (e.g. proteins, DNA), transport nutrients, and for processes such as locomotion. Life appears to be a direct violation of the basic laws of Thermodynamics, but it's not. Thermodynamics tells us that heat flows from hot temperatures to cold. So how can a refrigerator exist? It does so by using electricity, a form of energy. Life is like this; it needs a continual source of energy to carry out its tasks.

Where do life forms get their energy?
Animals oxidize their food and plants harvest sunlight using chlorophyll. Before the energy can be used, however, it must be transformed into a form that the organism can handle, store, and transport easily.

ATP = Life's Battery
A(adenosine)T(tri)P(phosphate) is composed of three components: In RED, the base consisting of linked rings of C and N atoms (adenine); In PINK, at the center is a sugar molecule (ribose, the lower right ring); in BLUE, a string of phosphate groups linked to the left (the most important).

When energy is needed, the organism breaks off the 1st HIGH ENERGY bond (Creating AD(di)P). If it needs still more energy, it can break off the 2nd bond (creating AM(mono)P). All life on Earth uses ATP for storing and controlling their energy. Later, when the organism is resting, the reverse reaction takes place, and the phosphate groups are re-attached. BUT THIS REQUIRES ENERGY!!

Energy Sources for Life
REDOX reactions: This is a combination of a reducing reaction and an oxidizing reaction essentially passing electrons from one molecule to another. There is a vast number of such chemical reactions available and organisms have adapted to use many of them.

PHOTOSYNTHESIS: Light energy is used to create high-energy chemical bonds and to "fix" CO₂ (an inorganic source of carbon) into organic carbon molecules.