In plants such as green algae, and cyanobacteria (blue-green algae), water is the electron source, while in photosynthetic bacteria, organic or sulfur compounds provide electron sources.
Anaerobic photosynthetic bacteria is a group of bacteria that do not produce oxygen during photosynthesis and only photosynthesize in environments that are devoid of oxygen. These bacteria use carbon dioxide and a substrate such as hydrogen sulfide to make carbohydrates. They have bacteriochlorophylls and other photosynthetic pigments that are similar to the chlorophylls used by higher plants. But, in contrast to higher plants, algae and cyanobacteria, the anaerobic photosynthetic bacteria have just one photosystem that is similar to PS-I. These bacteria likely represent a very ancient photosynthetic microbe.
Photosynthesis is central to all life on the planet and has been for many thousands of years. As a result, there are numerous variations in the way it occurs in different cells. The efficient collection of carbon dioxide mentioned earlier is one example of variation in photosynthesis. Other differences occur when the process takes place in bacteria rather than plants. Nonetheless, the description provided here outlines the basic concepts that would be noted in all photosynthesis. These differences pose the research questions that continue to challenge scientists today.
The carbon dioxide needed for this step enters through pores in the photosynthetic leaf (called stromata). Plants close these pores during hot, dry times of the day (to prevent water loss) so the details of carbon fixing vary for plants from different climates. In hot climates, where stomata are closed for a higher percentage of time, the trapping of carbon dioxide has to be more efficient than in cooler climates. This biochemical difference in photosynthesis helps explain why plants from one climate do not grow as well in warmer (or cooler) places.
Figure 2.2 - Schematic representation of mechanisms involved in bacterial photosynthesis CO2-fixing reactions do not produce energy during bacterial photosynthesis (i.e equimolar amounts of organic compounds are produced through decomposition of organic compounds), except when sulfur compounds serve as electron carriers.
Plants capture light using the pigment , which gives them their . This is contained in (compartments within the ) called . Although all green parts of a plant have chloroplasts, most of the energy is produced in the . The cells in the interior tissues of a leaf, called the , contain about half a million chloroplasts for every square of leaf. The surface of the leaf is uniformly coated with a water-resistant, , that, protects the leaf from excessive absorption of light and evaporation of water. The transparent, colourless layer allows light to pass through to the mesophyll cells where most of the photosynthesis takes place.
Photosynthesis occurs in plants and some bacteria, wherever there is sufficient sunlight - on land, in shallow water, even inside and below clear ice.
Algae range from multicellular forms like to , single-celled organisms. Although they are not as complex as land plants, photosynthesis takes place in the same way. Light is absorbed by chlorophyll, although various accessory pigments give them a wide variety of colors, located inside chloroplasts. All algae produce oxygen, and many are autotrophic. However, some are , relying on materials produced by other organisms.
Photosynthetic bacteria do not have chloroplasts. Instead, photosynthesis takes place directly within the cell. The contain chlorophyll and oxygen, in the same way that chloroplasts do - in fact chloroplasts are now considered to have developed from them. The other photosynthetic bacteria have a variety of different pigments, called , and do not produce oxygen.
Nitrogen is an element vital to all life processes on Earth. Nitrogen is very important in our biosphere, where nitrogen comprises 78% of the atmosphere, and is part of every living tissue. It is a component of amino acids, proteins and nucleic acids. With the exception of carbon, nitrogen is the most universal element of life. Life could not exist without nitrogen. .
Nitrogen is essential for organic development; nitrogenous compounds are also required by some organisms for metabolic functions and respiration. Unfortunately, free nitrogen in the atmosphere is not in a form that is usable by plants or animals. Because of its stable structural formula, it is relatively inert and does not combine readily with other elements.
All living organisms, from fish to plants, have great quantities of assimilated nitrogen in their tissues. Nitrogen is a fundamental ingredient for the formation of proteins and nucleic acids. Every organism you place in your aquarium adds nitrogen based compounds; from fish to coral, to live rock, to plants.
The introduction of food also adds nitrogen. Dead or alive, they are organic masses, and possess the same nitrogenous attributes as the fish, plants, invertebrates you added to your aquarium.
Inorganic nitrogen is added two ways: the atmosphere and new water. Atmospheric nitrogen (N2) is incorporated into our aquarium water by way of nitrogen fixing bacteria and by Cyanobacteria (bacteria that obtain their energy through photosynthesis) as ammonia (NH3). Some Cyanobacteria fix nitrogen gas, which cannot be used by plants, into ammonia, nitrites (NO2-) or nitrates (NO3-). Nitrates can then be utilized by plants and converted to nucleic acids and protein.
Inorganic nitrogenous compounds from our tap or well water also enter our aquarium, often as Nitrites or Nitrates. Reverse Osmosis can remove much of this.
For more about tap water, please see this article:
When exposed to water, light, and carbon dioxide, the crystals on these bacteria make acetic acid—vinegar, basically. This reaction is around 80 percent efficient, more than six times as efficient as regular photosynthesis. More importantly, all it takes is bacteria and some cadmium for the reaction to start taking place.
Photosynthesis takes place inside plant cells in small things called chloroplasts. Chloroplasts contain a green substance called chlorophyll. This absorbs the light energy needed to make photosynthesis happen. Plants can only photosynthesise in the light.