Concept explainers
To review:
The source and sink of electrons in respiration, lithotrophy, and photolysis.
Introduction:
An electron transport chain is a series of reactions in which the electron carrier transfers the electron to the carrier of the next- higher reduction potential (E) in a sequential manner. The electron flow is initiated with an initial electron donor from the outside of the cell that transfers the electrons to a terminal electron acceptor leaving the cell.
Explanation of Solution
Lithotrophy is an energy-yielding form of
In the process of photosynthesis, energy is derived from the photoexcitation of the light-absorbing pigment. The process of photolysis which is a light-driven separation of an electron from a molecule coupled to an electron transport chain is a consequence of photoexcitation. Photolysis is termed as “ light-reactions� that is coupled to “light-independent reactions� of carbon dioxide fixation in the plant chloroplast and cyanobacteria. The process of photoexcitation in ETS (electron transport system)-based photosynthesis causes the separation of the electron from a donor molecule like H2O (water) or H2S (hydrogen sulfide). The electrons are then transferred to an electron transport system which produces a proton potential and the reduced cofactor NADPH (nicotinamide adenine dinucleotide phosphate hydrogen). Proton potential is responsible to drive ATP (adenosine triphsophate) synthesis through an F1 and F0 ATP synthase.
Bacteria that are obligate aerobes grow only by using oxygen as the terminal electron acceptor like Sinorhizobiummeliloti. Although in anaerobic respiration, some bacteria and Archae use terminal electron acceptors like metals, oxidized ions of nitrogen and sulphur, and chlorinated organic molecules. In Escherichiacoli,different terminal oxidoreductases to reduce alternative electron acceptors are present which are termed as “reductases�. Some of the inorganic electron acceptors are nitrate (NO3) reduced to nitrite (NO2-) or NO2- reduced to NO (nitric oxide). The organic electron acceptors also play an important role in the process of food decomposition. In aerobic bacteria, the respiratory electron transport system leads to the formation of water by receiving electrons from NADH and FADH2 (flavin adenine dinucleotide dihydrogen) and transferring them to oxygen.
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Chapter 14 Solutions
Microbiology: An Evolving Science (Fourth Edition)
- List the products of linear electron transport and cyclic electron transport, and describe the role of cyclic electron transport.arrow_forwardExplain why electron transport in purple photosynthetic bacteria follows a circular path.arrow_forwardDescribe the flow of electrons through photosystems I and II in the noncyclic electron transport pathway and the products produced. Contrast this flow with cyclic electron transport.arrow_forward
- Explain the process of electron transfer phosphorylationarrow_forwardAssume a thylakoid is somehow punctured so that the interior of the thylakoid is no longer separated from the stroma but the photosystems and membrane proteins of the electron transport chain are unharmed. This damage will have the most direct effect on which of the following processes?arrow_forwarda) Label PSI Diagram 6 and PSII. Thylakold stroma b) Draw the path of the electron transport chain Thytakoid lumenarrow_forward
- Indicate whether the statement is true for aerobic respiration, photosynthesis or both: ATP Synthase converts potential energy to chemical energy to synthesize ATP, and is powered by an electrochemical proton (H+) gradient a)Aerobic Respiration b)Photosynthesis c)Botharrow_forwardIndicate whether the statement is true for aerobic respiration, photosynthesis or both: NADH is oxidized to NAD+ at complex I a)Aerobic Respiration b)Photosynthesis c)Botharrow_forwardThylakoids were isolated from chloroplasts and incubated in the dark in an acidic solution (pH 4) to equilibrate the pH. After 30 minutes, the thylakoids were transferred to a basic solution (pH 8) and kept in the dark. Will this system produce ATP? Explain. Will this system produce G3P? Explain.arrow_forward
- For the following questions, choose one to discuss: chloroplast/photosynthesis State at the outset which one you will discuss. A) What role do proton gradients play in the process of photosynthesis proton gradients allow B) Where are proton gradients formed? Within what structures are they seen in chloroplasts How do the structures help them to maintain a gradient? C) Explain where and how the chloroplast or mitochondria uses passive transport and active transport to complete photosynthesis or cellular respiration.arrow_forwardCompare and contrast the processes of cyclic and non cyclic phosphorylation as follows: 1. Source of electrons (Donor) 2. Final acceptor of electrons 3. Products 4. Pathway of electron flow 5. Photosystems involvedarrow_forwardDescribe in detail the structure and function of the electron transport chain. Discuss how the light-dependent reactions and the Calvin cycle act synergistically to produce food for plants.arrow_forward
- Concepts of BiologyBiologyISBN:9781938168116Author:Samantha Fowler, Rebecca Roush, James WisePublisher:OpenStax College