Electron flows, or electron transport, is a critical step in numerous biochemical pathways. For example, the flow of electrons along the electron transport chain between membrane-bound proteins of mitochondria during cellular respiration or the chloroplast during photosynthesis triggers a flow of protons across the same membrane. This flow provides the energy for cellular processes similar to the flow of water across a hydroelectric dam.
Electron transport is essential for helping organisms to produce energy and survive. Several species can modify the movement of electrons in different ways, allowing them to survive in a variety of conditions.
Oxidation state refers to the degree to which an element has gained or lost electrons–it can have a significant impact on the characteristics of that element. For example, hexavalent chromium with an oxidation number of +6, is a known carcinogen whereas the less oxidized (i.e., “reduced”) trivalent form, with an oxidation number of +3, is less toxic. The bacterium, Acidiphilium cryptum, can enzymatically convert chromium from the hexavalent to the trivalent form.
The vast majority of biochemical assembly and breakdown processes–even by the most complex organisms–occur within cells. In fact, cells are able to perform hundreds, even thousands of chemical transformations at the same time under life-friendly conditions (ambient temperature and pressure in an aqueous environment). For example, inorganic pyrophosphate is hydrolyzed to form two phosphate groups in the cellular degradation pathway of fatty acids.
Living systems often require chemical elements and chemical compounds, including complex sugars, proteins, and odor-making compounds, to perform critical activities. These compounds exist in various states–solid, liquid, and gas–and are ubiquitous in soil, water, and air. This requires that living systems not only have ways to capture, absorb, or filter them, but also ways to differentiate among them, selecting those that are valuable or harmful. For example, mangrove trees live with their roots in salty water and sediments. Various mangrove species have different strategies for removing salt from the water they take in so that their tissues can use the fresh water.
Domain Bacteria (“small staff”): L. acidophilus, Staphylococcus
From inside of our own bodies to the deepest parts of the ocean, bacteria have adapted to almost every possible environment. All bacteria are unicellular, microscopic, and lack a membrane-bound nucleus and organelles, and come in three basic shapes: spherical (cocci), rod (bacilli), and spiral (spirilla). Some strains can be deadly, like Staphylococcus aureus (MRSA) while others, like Lactobacillus acidophilus, found in our intestinal microbiome, keep us healthy. Cyanobacteria, also known as blue green algae, caused the Great Oxidation Event 2.4 billion years ago, producing Earth’s first oxygenated atmosphere.
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