Key difference - chemosynthesis vs. photosynthesis
Chemosynthesis and photosynthesis are the two main production mechanisms by which organisms produce their own food. Both processes are involved in the production of simple sugars like glucose from carbon dioxide and water. The main difference between chemosynthesis and photosynthesis is that chemosynthesis is the process by which the organic compounds in the cell are synthesized by the energy generated by chemical reactions , while photosynthesis is the process by which organic compounds are synthesized by those from sunlight recovered energy can be synthesized.
This article is about,
1. What is chemosynthesis - definition, properties, process 2. What is photosynthesis - definition, properties, process 3. What is the difference between chemosynthesis and photosynthesis?
What is Chemosynthesis?
Chemosynthesis is the synthesis of organic compounds using energy obtained through the oxidation of inorganic compounds. Chemosynthesis takes place in the absence of sunlight, for example at hydrothermal springs in the deep sea. Organisms that live in hydrothermal springs use inorganic compounds that come from the sea floor as an energy source for the production of food. Hydrothermal springs therefore consist of high biomass including a sparse distribution of animals that rely on food to fall down through chemosynthesis. Chemosynthesis is mainly carried out by microbes that are found on the ocean floor and form microbial mats. Scale worms, limpets, and slugs like grass-eaters can be found on the mat they eat. Predators also come and eat these grazers. Animals like tube worms live as symbionts with chemosynthetic bacteria. Giant tube worms next to a hydrothermal spring are shown in Figure 1 .
Figure 1: Giant tubeworms next to a hydrothermal spring
In chemosynthesis, bacteria use the energy stored in chemical bonds from hydrogen sulfide or hydrogen gas to produce glucose from dissolved carbon dioxide and water. The chemical reaction to utilize hydrogen sulfide in chemosynthesis is shown below.
12 H 2 S + 6C O 2 → C 6 H 12 O 6 (glucose) + 6 H 2 O + 12 S
The organisms that perform chemosynthesis are called chemotrophs . Chemoorganotrophs and chemolithotrophs are the two categories of chemotrophs. Chemolithotrophe use electrons from inorganic chemical sources such as hydrogen sulfide, ammonium ions, iron ions, and elemental sulfur. Acidithiobacillus ferrooxidans which is an iron bacterium, Nitrosomonas which is a nitrosifying bacterium, Nitrobactor which is a nitrifying bacterium, sulfur oxidizing proteobacteria, aquificaeles and methanogenic archaea are the examples of chemolithotrophe.
What is photosynthesis?
Photosynthesis is the process by which the green plants and algae synthesize glucose to form carbon dioxide and water using sunlight as a source of energy. The pigment chlorophyll is involved in this process. In plants, photosynthesis takes place in specialized plastids, the chloroplasts . Higher plants are made up of leaves that contain more chlorophyll in order to carry out photosynthesis efficiently.
Figure 2: Photosynthetic leaves
Two categories of photosynthesis are found: oxygenic photosynthesis and anoxygenic photosynthesis. Oxygen photosynthesis occurs in cyanobacteria, algae, and plants, while anoxygenic photosynthesis occurs in purple sulfur bacteria and green sulfur bacteria. During photosynthesis containing oxygen, electrons are transferred from water to carbon dioxide. In the process, water is oxidized and carbon dioxide is reduced, creating glucose. Therefore, the electron donor in oxygen-containing photosynthesis is water. Oxygen gas is a by-product of photosynthesis containing oxygen. In contrast, anoxygenic photosynthesis does not produce oxygen as a by-product. The electron donor is variable and can be hydrogen sulfide. The chemical reactions of both oxygenated and anoxygenic photosynthesis are shown below.
Oxygen photosynthesis:
6 C O 2 + 12H 2 O + light energy → C 6 H 12 O 6 + 6 O 2 + 6H 2 O
Anoxygenic photosynthesis:
C O 2 + 2H 2 S + light energy → [ C H 2 O] + 2 S + H 2 O
The organisms that photosynthesize are called phototrophs . Photoautotrophs and photoheterotrophs are the two categories of phototrophs. The carbon source of photoautotrophs is carbon dioxide, while the carbon source of photoheterotrophs is organic carbon. Green plants, cyanobacteria and algae are examples of photoautotrophs and some bacteria such Rhodobactor are examples of Photoheterotrophe.
Difference Between Chemosynthesis and Photosynthesis
Energy source
Chemosynthesis: The energy source for chemosynthesis is the chemical energy that is stored in inorganic chemicals such as hydrogen sulfide.
Photosynthesis: The energy source for photosynthesis is sunlight.
Energy conversion
Chemosynthesis: Chemical energy stored in inorganic compounds is stored in organic compounds during chemosynthesis.
Photosynthesis: During photosynthesis, the light energy is converted into chemical energy.
Organisms
Chemosynthesis: Chemosynthetic organisms are collectively referred to as chemotrophs.
Photosynthesis: Photosynthetic organisms are collectively referred to as phototrophs.
Pigments involved
Chemosynthesis: No pigments are involved in chemosynthesis.
Photosynthesis: Chlorophyll, carotenoids and phycobilins are the pigments that are involved in photosynthesis.
Involved plastids
Chemosynthesis: Plastids are not involved in chemosynthesis.
Photosynthesis: Chloroplasts are the plastids found in plants; photosynthesis reactions are concentrated in the cell.
Oxygen as a by-product
Chemosynthesis: Oxygen gas is not released as a by-product.
Photosynthesis: During photosynthesis , oxygen is released as a by-product.
Contribution to the total biosphere energy
Chemosynthesis: Chemosynthesis has a smaller contribution to the total biosphere energy.
Photosynthesis: Photosynthesis has a higher contribution to the total biosphere energy.
Categories
Chemosynthesis: Chemoorganotrophs and Chemolithotrophs are the two categories of chemotrophs.
Photosynthesis: Photoautotrophs and photoheterotrophs are the two categories of phototrophs.
presence
Chemosynthesis: Chemosynthesis is found in bacteria such as Acidithiobacillus ferrooxidans, Nitrosomonas, Nitrobacter, sulfur-oxidizing proteobacteria, aquificaeles, and archaea such as methanogenic archaea.
Photosynthesis: Photosynthesis occurs in green plants, cyanobacteria, algae and rhodobactor- like bacteria.
diploma
Chemosynthesis and photosynthesis are two types of primary productions that occur in organisms. Chemosynthesis and photosynthesis fuel all life forms on earth. Most chemosynthetic as well as photosynthetic organisms use carbon dioxide and water to produce organic compounds for food. Chemosynthesis uses the chemical energy stored in inorganic compounds to produce simple sugars such as glucose. It is the primary source of energy for most animals found in hydrothermal springs in the deep sea that sunlight cannot reach. In contrast, photosynthesis uses the sun's light energy to produce glucose. Chemosynthesis is mainly found in bacteria, which can either live independently on the ocean floor, or symbionts, which live in animals like tube worms by replacing their viscera. Land plants are the main producers of most of the world's food chains. However, the main difference between chemosynthesis and photosynthesis is their source of energy.
Reference: 1. National Research Council (US) Committee on Research Opportunities in Biology. “Ecology and Ecosystems.” Opportunities in Biology. US National Library of Medicine, Jan. 1, 1989. Web. 03 Apr 2017. 2nd National Research Council (US) Ocean Studies Board. "Achievements in Biological Oceanography." 50 Years of Ocean Discovery: National Science Foundation 1950-2000. US National Library of Medicine, January 1, 1970. Web. April 3, 2017. 3. Cooper, Geoffrey M. "Photosynthesis". The cell: a molecular approach. 2nd Edition. US National Library of Medicine, January 1, 1970. Web. 04/03/2017.
Image courtesy of: 1. " Giant tubeworms next to the vent" From NASA - (Public Domain) via Commons Wikimedia 2. "318743" (Public Domain) via Pixabay
