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ATP synthase is an enzyme that spans the cytoplasmic membrane. H+ flow in through this protein from the outside of the cytoplasmic membrane into the cytoplasm. On the inner side of the protein, this flow of H+ is used to build ATP from ADP and Pi.
The bacterial electron transport chain is a series of protein complexes, electron carriers, and ion pumps that is used to pump H + out of the bacterial cytoplasm into the extracellular space. H + flows back down the electrochemical gradient into the bacterial cytoplasm through ATP synthase, providing the energy for ATP production by oxidative phosphorylation.(credit: modification of work by Klaus Hoffmeier)

The number of ATP molecules generated from the catabolism of glucose varies. For example, the number of hydrogen ions that the electron transport system complexes can pump through the membrane varies between different species of organisms. In aerobic respiration in mitochondria, the passage of electrons from one molecule of NADH generates enough proton motive force to make three ATP molecules by oxidative phosphorylation, whereas the passage of electrons from one molecule of FADH 2 generates enough proton motive force to make only two ATP molecules. Thus, the 10 NADH molecules made per glucose during glycolysis, the transition reaction, and the Krebs cycle carry enough energy to make 30 ATP molecules, whereas the two FADH 2 molecules made per glucose during these processes provide enough energy to make four ATP molecules. Overall, the theoretical maximum yield of ATP made during the complete aerobic respiration of glucose is 38 molecules, with four being made by substrate-level phosphorylation and 34 being made by oxidative phosphorylation ( [link] ). In reality, the total ATP yield is usually less, ranging from one to 34 ATP molecules, depending on whether the cell is using aerobic respiration or anaerobic respiration; in eukaryotic cells, some energy is expended to transport intermediates from the cytoplasm into the mitochondria, affecting ATP yield.

[link] summarizes the theoretical maximum yields of ATP from various processes during the complete aerobic respiration of one glucose molecule.

In glycolysis (EMP) carbon moves from glucose (6C) to 2 pyruvate (3C). The molecules of reduced coenzyme produced are 2 NADH. The net ATP molecules made by substrate level phosphorylation is 2 ATP. The net ATP molecules made by oxidative phosphorylation is 6 ATP from 2 NADH. The theoretical maximum yield of ATP molecules is 8. In the transition reaction carbon moves from 2 pyruvate (3C) to 2 acetyl (2C) + 2 CO2. The molecules of reduced coenzyme produced are 2 NADH. The net ATP molecules made by substrate level phosphorylation is 0 ATP. The net ATP molecules made by oxidative phosphorylation is 6 ATP from 2 NADH. The theoretical maximum yield of ATP molecules is 6. In the Krebs cycle carbon moves from 2 acetyl (2C) to 4 CO2. The molecules of reduced coenzyme produced are 6 NADH and 2 FADH2. The net ATP molecules made by substrate level phosphorylation is 2 ATP. The net ATP molecules made by oxidative phosphorylation is 18 ATP from 6 NADH and 4 ATP from 2 FADH2. The theoretical maximum yield of ATP molecules is 24. In total carbon moves from glucose (6C) to 6 CO2. The molecules of reduced coenzyme produced are 10 NADH and 2 FADH2. The net ATP molecules made by substrate level phosphorylation is 4 ATP. The net ATP molecules made by oxidative phosphorylation is 34 ATP. The theoretical maximum yield of ATP molecules is 38.
  • What are the functions of the proton motive force?

Key concepts and summary

  • Most ATP generated during the cellular respiration of glucose is made by oxidative phosphorylation .
  • An electron transport system (ETS) is composed of a series of membrane-associated protein complexes and associated mobile accessory electron carriers. The ETS is embedded in the cytoplasmic membrane of prokaryotes and the inner mitochondrial membrane of eukaryotes.
  • Each ETS complex has a different redox potential, and electrons move from electron carriers with more negative redox potential to those with more positive redox potential.
  • To carry out aerobic respiration , a cell requires oxygen as the final electron acceptor. A cell also needs a complete Krebs cycle, an appropriate cytochrome oxidase, and oxygen detoxification enzymes to prevent the harmful effects of oxygen radicals produced during aerobic respiration.
  • Organisms performing anaerobic respiration use alternative electron transport system carriers for the ultimate transfer of electrons to the final non-oxygen electron acceptors.
  • Microbes show great variation in the composition of their electron transport systems, which can be used for diagnostic purposes to help identify certain pathogens.
  • As electrons are passed from NADH and FADH 2 through an ETS, the electron loses energy. This energy is stored through the pumping of H + across the membrane, generating a proton motive force .
  • The energy of this proton motive force can be harnessed by allowing hydrogen ions to diffuse back through the membrane by chemiosmosis using ATP synthase . As hydrogen ions diffuse through down their electrochemical gradient, components of ATP synthase spin, making ATP from ADP and P i by oxidative phosphorylation.
  • Aerobic respiration forms more ATP (a maximum of 34 ATP molecules) during oxidative phosphorylation than does anaerobic respiration (between one and 32 ATP molecules).

Fill in the blank

The final ETS complex used in aerobic respiration that transfers energy-depleted electrons to oxygen to form H 2 O is called ________.

cytochrome oxidase

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The passage of hydrogen ions through ________ down their electrochemical gradient harnesses the energy needed for ATP synthesis by oxidative phosphorylation.

ATP synthase

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True/false

All organisms that use aerobic cellular respiration have cytochrome oxidase.

True

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Short answer

What is the relationship between chemiosmosis and the proton motive force?

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How does oxidative phosphorylation differ from substrate-level phosphorylation?

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How does the location of ATP synthase differ between prokaryotes and eukaryotes? Where do protons accumulate as a result of the ETS in each cell type?

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Questions & Answers

difference btwn hausteria and appears
Raviha Reply
numerical and molecular taxanomy
Dhanshri Reply
difference btwn hausteria and appesorium
Raviha
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Emmah Reply
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namugenyi Reply
never recap or bend a sharp objects
benita
describe the process of platelet formation
Joy Reply
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Sadiya Reply
list three categories of symbiotic relationships.
mary Reply
parasitis,mutualism and comensalism.
mary
what's the difference between microbial intoxication and infectious diseases
dranimva Reply
microbial intoxication results when a person ingests a toxin or a poisonous substance that has been produced by a microbe while infectious disease results when a pathogen colonize the body and subsequently cause disease.
mary
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amna Reply
It is mainly used for media preparation and product testing purpose.
Nakaweesi
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nuur
what is microbiology
Shamsuddeen Reply
study of living organisms that are too small to be visible with naked eye
Marah
yes
Ahmed
microbiology is the study of microscopic organisms, either unicellular(single cell), multicellular( cell colony), or acellular (lacking cell).
munachimso
Microbiology is the study of microorganisms that cannot be seen with the necked eyes but by the help of microscope.
Fuseini
is the word Atypical or a typical bacteria. .am confused pliz help
MUWANGUZI Reply
typical bacteria
Zulpha
okay thank you what does that mean
MUWANGUZI
atypical means that it has some characters from bacteria not all characters ...but tybical means that it has all the characters that bacteria have
Reham
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MUWANGUZI
some examples please
MUWANGUZI
thank you Reham
MUWANGUZI
1) typical bacteria contain a cell wall whereas atypical bacteria usually do not contain a cell . 2) typical bacteria can be either Gram-positive or Gram-negative while atypical bacteria remain colorless with Gram staining. 3) cells of typical bacteria are large ,while cells of the atypical small
Marah
Example of atypical : Mycoplasma pneumoniae , chlamydophila pneumoniae , legionella
Marah
what is micro biology
Jauharah Reply
is the study of organisms which can't be viewed by our necked eyes
Egumat
Because it preexisting causing secondary infection after collateral damage of normal microbota
Rafaa Reply
combinations of drugs that can't be taken together and why
Grace Reply
Antagonism: the combined action is less than that of the more effective agent when used alone). All these effects may be observed in vitro (particularly in terms of bactericidal rate) and in vivo والله اعلم
Lenovo
....fermentros have 1-15litre capacity
AMAR Reply
Practice MCQ 5

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Source:  OpenStax, Microbiology. OpenStax CNX. Nov 01, 2016 Download for free at http://cnx.org/content/col12087/1.4
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