How2Day: What Other Organisms Have Photosynthesis?

The chemical crucial to photosynthesis is what gives plants their green color. herbe image by Claudio Calcagno from Fotolia.com
To photosynthesize is to create chemically using light. Most commonly, it denotes the production of sugars by organisms that receive the light of the sun. Such organisms are known as phototrophs. Photosynthesis is not exclusive to plants. Algae, certain bacteria and animals---in a way---conduct photosynthesis as well.

Photosynthesis in plants typically takes place in the leaves. Little to no photosynthesis occurs in the stems, flowers and other plant parts. Cells in the leaves contain organelles called chloroplasts. A pigment called chlorophyll, located in the chloroplast, absorbs all wavelengths of light from the sun except for green light, giving plants their green color. Photons from the rest of the light, as they hit the chlorophyll, initiate a chain of electron transfers. If water and carbon dioxide are both available, the chloroplast will be able to generate adenosine triphosphate, or ATP, which the plant converts afterward into sugar. A biproduct of the reaction is oxygen.

Water serves as an electron donor in the reaction; certain other molecules can substitute, but this is rare in plants. Because sunlight and usually water are necessary for plants to produce sugars, and therefore energy, these are the two most essential elements that a gardener considers when planting and maintaining her crops.

Some algae conduct photosynthesis in chloroplasts like plants do, while others do so in infolded cytoplasmic membranes known as thylakoid membranes. Many algae are described as mixotrophic, which means that they derive some of their energy from sunlight, and the rest through direct carbon uptake. Algae are classified as eukaryotic creatures, meaning that the organelles, or sub-organs, in their cells are bound by membranes.

Scientists classify bacteria that obtain their energy through photosynthesis as cyanobacteria. They are ubiquitous creatures, found in oceans, fresh water, bare rock, soil and elsewhere. Some of them live in the fur of sloths. Colonies of these microscopic organisms can take the forms of films, sheets, filaments and even hollow balls.

Animals do not use sunlight in a reaction that produces energy the way that plants and other organisms do. However, sunlight is a key to the process by which animals produce vitamin D, and this could be considered a form of photosynthesis. When someone is exposed to sunlight, the rays react with a cholesterol in the body known as provitamin D. The ensuing reaction takes two to three days to complete, but it yields vitamin D by the end. Vitamin D plays a role in neuromuscular function, reduces inflammation, and helps defend the body against microbial invaders.

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