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Aerobic Cellular Respiration: Stages, Equation & …

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AB - Cyanobacterial thylakoids catalyze both photosynthetic and respiratory activities. In a photosystem I-less Synechocystis sp. PCC 6803 strain, electrons generated by photosystem II appear to be utilized by cytochrome oxidase. To identify the lumenal electron carriers (plastocyanin and/or cytochromes c553, c550, and possibly C(M)) that are involved in transfer of photosystem II-generated electrons to the terminal oxidase, deletion constructs for genes coding for these components were introduced into a photosystem I-less Synechocystis sp. PCC 6803 strain, and electron flow out of photosystem II was monitored in resulting strains through chlorophyll fluorescence yields. Loss of cytochrome c553 or plastocyanin, but not of cytochrome c550, decreased the rate of electron flow out of photosystem II. Surprisingly, cytochrome cM could not be deleted in a photosystem I-less background strain, and also a double-deletion mutant lacking both plastocyanin and cytochrome c553 could not be obtained. Cytochrome c(M) has some homology with the cytochrome c-binding regions of the cytochrome caa3-type cytochrome oxidase from Bacillus spp. and Thermus thermophilus. We suggest that cytochrome c(M) is a component of cytochrome oxidase in cyanobacteria that serves as redox intermediate between soluble electron carriers and the cytochrome aa3 complex, and that either plastocyanin or cytochrome c553 can shuttle electrons from the cytochrome b6f complex to cytochrome C(M).

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Cyanobacterial thylakoids catalyze both photosynthetic and respiratory activities. In a photosystem I-less Synechocystis sp. PCC 6803 strain, electrons generated by photosystem II appear to be utilized by cytochrome oxidase. To identify the lumenal electron carriers (plastocyanin and/or cytochromes c553, c550, and possibly C(M)) that are involved in transfer of photosystem II-generated electrons to the terminal oxidase, deletion constructs for genes coding for these components were introduced into a photosystem I-less Synechocystis sp. PCC 6803 strain, and electron flow out of photosystem II was monitored in resulting strains through chlorophyll fluorescence yields. Loss of cytochrome c553 or plastocyanin, but not of cytochrome c550, decreased the rate of electron flow out of photosystem II. Surprisingly, cytochrome cM could not be deleted in a photosystem I-less background strain, and also a double-deletion mutant lacking both plastocyanin and cytochrome c553 could not be obtained. Cytochrome c(M) has some homology with the cytochrome c-binding regions of the cytochrome caa3-type cytochrome oxidase from Bacillus spp. and Thermus thermophilus. We suggest that cytochrome c(M) is a component of cytochrome oxidase in cyanobacteria that serves as redox intermediate between soluble electron carriers and the cytochrome aa3 complex, and that either plastocyanin or cytochrome c553 can shuttle electrons from the cytochrome b6f complex to cytochrome C(M).

Which definition, what one?: Which of these do you want? Which do you want? See more.

When O acquires 4 electrons and 2 protons, it is converted into water, which is released as a waste product.

The oxidized electron carriers are fed back into glycolysis, and the citric acid cycle.
Chemiosmosis!
How ATP is produced.

The ETC establishes a proton (aka "
electrochemical
") gradient.

Protons can only diffuse back in to the matrix through a protein channel.

ATP synthase
: The only proton channel available in the inner membrane.

As protons diffuse through ATP synthase, the free energy that is released is used to catalyze ATP formation from ADP and free phosphate groups ("
oxidative phosphorylation
")
Fun Fact:
Chemiosmosis was proposed by Peter Mitchell, who won a Nobel Prize for his efforts in 1978.

It is the major mechanism by which ATP is produced in aerobic cellular respiration AND photosynthesis.
Inputs
Outputs
10 NADH
2 FADH
O
per glucose
per glucose
2
2
~32-34 ATP
H O
10 NAD+
2 FAD+
2
Why it's impossible to get a straight answer
A natural question:
How much ATP is produced per glucose?

Can't be answered any more exactly than something like "32-36".

Why?
Decoupling of glucose oxidation and oxidative phosphorylation.
Roughly:
3 ATP per NADH
2 ATP per FADH
2
Efficiencies
Anaerobic
If we consider a hypothetical maximum of 38 ATP per glucose molecule, aerobic cellular respiration is 19X more efficient than anaerobic cellular respiration in terms of usable energy generated.
Aerobic In Depth
Aerobic cellular respiration is ~40% efficient in terms of converting chemical energy in glucose into chemical energy in ATP.

By comparison, your car is ~15% efficient at converting the chemical energy in gasoline into mechanical energy.
How do living systems process energy?
This chimpanzee would die if it didn't eat.

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