unit 5 cc5

Methanogenesis is the process of producing methane from carbon dioxide and hydrogen. The reaction can be represented as CO2 + 4H2 -> CH4 + 2H2O. It is carried out by a group of archaea called methanogens.

Phototrophic organisms can be divided into two groups based on the presence or absence of oxygen as a byproduct of photosynthesis: anoxygenic phototrophs and oxygenic phototrophs.

Examples of anoxygenic phototrophs include purple bacteria, which produce hydrogen from water and carbon dioxide, and green sulfur bacteria, which produce sulfur from hydrogen sulfide and carbon dioxide.

Examples of oxygenic phototrophs include cyanobacteria, which are the most common oxygenic phototrophs and are found in various habitats, green algae, found in fresh and salt water and important components of aquatic ecosystems, and plants, which are essential for life on Earth as they produce the oxygen that we breathe.

The basic steps of photosynthesis in green bacteria, purple bacteria, and cyanobacteria are: 1. Light absorption, where light energy is absorbed by pigments in the photosynthetic apparatus. 2. Electron transport, where the absorbed light energy is used to transfer electrons from water to carbon dioxide. 3. Carbon fixation, where carbon dioxide is fixed to form organic molecules. 4. Regeneration of RuBP, where the organic molecules are used to regenerate the carbon dioxide acceptor, RuBP.

The main difference lies in the type of pigment they use to absorb light energy. Green bacteria use chlorophyll a, which absorbs light in the green and blue regions of the spectrum. Purple bacteria use bacteriochlorophyll a, which absorbs light in the purple and red regions of the spectrum. Cyanobacteria use phycobiliproteins, which absorb light in the green, yellow, and orange regions of the spectrum.

Methanogens are a group of archaea responsible for carrying out the process of methanogenesis. They play a crucial role in converting carbon dioxide and hydrogen into methane, contributing to the global methane cycle.

Phototrophic organisms use light energy to synthesize organic molecules and obtain their carbon from carbon dioxide. They play a key role in the conversion of light energy into chemical energy through the process of photosynthesis.

Anoxygenic phototrophs do not produce oxygen as a byproduct of photosynthesis. Instead, they produce other compounds such as hydrogen or sulfur. Oxygenic phototrophs, on the other hand, produce oxygen as a byproduct of photosynthesis.

Cyanobacteria are found in a wide variety of habitats, including fresh water, salt water, and soil. Green algae are found in fresh water and salt water, and plants are also found in diverse habitats. While cyanobacteria and green algae are aquatic, plants can be found in terrestrial as well as aquatic environments.

The absorption of light energy differs based on the type of pigment used by each group. Green bacteria use chlorophyll a, which absorbs light in the green and blue regions, purple bacteria use bacteriochlorophyll a, which absorbs light in the purple and red regions, and cyanobacteria use phycobiliproteins, which absorb light in the green, yellow, and orange regions.

Producing oxygen as a byproduct of photosynthesis is significant as it contributes to the oxygen cycle and is essential for sustaining aerobic life forms on Earth.

H2 + 1/2 O2 -> H2O

1. Nitrosomonas: oxidize ammonia to nitrite; 2. Nitrospira: oxidize nitrite to nitrate

1. Methanogens: use carbon dioxide and hydrogen; 2. Thiobacillus denitrificans: use sulfur with nitrate as the electron acceptor

The energy from the oxidation of inorganic compounds

Aerobic chemolithotrophs use oxygen as the electron acceptor, while anaerobic chemolithotrophs use other inorganic compounds such as sulfur or nitrate

Hydrogen oxidation

Organisms that use the energy from the oxidation of inorganic compounds to synthesize organic molecules, obtaining carbon from carbon dioxide

Iron bacteria: oxidize ferrous iron to ferric iron

The oxidation reactions provide energy for the synthesis of organic molecules from inorganic compounds

Oxygen serves as the electron acceptor in the energy-producing reactions of aerobic chemolithotrophs

Methanogens produce methane from carbon dioxide and hydrogen

The energy released can be used to produce ATP

Chemolithotrophs are organisms that use the energy from the oxidation of inorganic compounds to synthesize organic molecules. They obtain their carbon from carbon dioxide.

Examples of aerobic chemolithotrophs include Nitrosomonas, Nitrospira, sulfur bacteria, and iron bacteria. They use oxygen as the electron acceptor in their energy-producing reactions.

Anaerobic chemolithotrophs do not use oxygen as the electron acceptor in their energy-producing reactions. Instead, they use other inorganic compounds, such as sulfur or nitrate. This is the main difference from aerobic chemolithotrophs.

Nitrosomonas and Nitrospira are aerobic chemolithotrophs that oxidize ammonia to nitrite and nitrite to nitrate, respectively.

Sulfur bacteria are aerobic chemolithotrophs that oxidize sulfur to sulfate, contributing to the process of aerobic chemolithotrophy.

Iron bacteria are aerobic chemolithotrophs that oxidize ferrous iron to ferric iron as part of their energy-producing reactions.

Anaerobic chemolithotrophs do not use oxygen as the electron acceptor in their energy-producing reactions. Instead, they use other inorganic compounds, such as sulfur or nitrate.

Examples of anaerobic chemolithotrophs include methanogens, which produce methane from carbon dioxide and hydrogen, and Thiobacillus denitrificans, which oxidizes sulfur to sulfate using nitrate as the electron acceptor.

Hydrogen oxidation is the process of oxidizing hydrogen to water. The energy released by this reaction can be used to produce ATP, making it relevant to chemolithotrophy.

The reaction for hydrogen oxidation is $H_2 + \frac{1}{2} O_2 \rightarrow H_2O$.

The oxidation of inorganic compounds provides the energy necessary for chemolithotrophs to synthesize organic molecules and sustain their metabolism.

The ability to use inorganic compounds as electron acceptors allows chemolithotrophs to carry out energy-producing reactions in environments where oxygen may be limited or absent.