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Water is ~11% hydrogen by mass but ~67% hydrogen by atomic percent, and these numbers along with the complementary % numbers for oxygen in water, are the largest contributors to overall mass and atomic composition figures. Because of water content, the human body contains more oxygen by mass than any other element, but more hydrogen by atom ...
Liquid hydrogen also has a much higher specific energy than gasoline, natural gas, or diesel. [12] The density of liquid hydrogen is only 70.85 kg/m 3 (at 20 K), a relative density of just 0.07. Although the specific energy is more than twice that of other fuels, this gives it a remarkably low volumetric energy density, many fold lower.
Typical eukaryotic cell. Cellular respiration is the process by which biological fuels are oxidized in the presence of an inorganic electron acceptor, such as oxygen, to drive the bulk production of adenosine triphosphate (ATP), which contains energy.
Lactic acid fermentation is relatively inefficient. The waste products lactic acid and ethanol have not been fully oxidized and still contain energy, but it requires the addition of oxygen to extract this energy. [8] Generally, lactic acid fermentation occurs only when aerobic cells are lacking oxygen.
Using electricity produced by photovoltaic systems potentially offers the cleanest way to produce hydrogen, other than nuclear, wind, geothermal, and hydroelectric. Again, water is broken down into hydrogen and oxygen by electrolysis, but the electrical energy is obtained by a photoelectrochemical cell (PEC) process.
Hormones are similarly rapidly and evenly spread to every cell in the body, regardless of where they are secreted into the blood. Oxygen taken up by the lungs from the alveolar air is also evenly distributed at the correct partial pressure to all the cells of the body. Waste products are also uniformly spread to the whole of the ECF, and are ...
Photosynthetic cells use the sun's energy to split off water's hydrogen from oxygen. [107] In the presence of sunlight, hydrogen is combined with CO 2 (absorbed from air or water) to form glucose and release oxygen. [108] All living cells use such fuels and oxidize the hydrogen and carbon to capture the sun's energy and reform water and CO
One of the two oxygen groups on the carboxylic acid are derived from a water molecule and the amine (or ammonia) gains the hydrogen ion. The hydrolysis of peptides gives amino acids. Many polyamide polymers such as nylon 6,6 hydrolyze in the presence of strong acids. The process leads to depolymerization. For this reason nylon products fail by ...