Question

From these pathways, the TCA cycle, electron transport chain, oxidative phosphorylation, β-oxidation for fatty acid degradation, ketone body metabolism, and lipid biosynthesis which ones are affected by low oxygen? Where in the cell do these pathways occur? Next, explain how reduced oxygen slows each pathway(s) identified. Once oxygen is no longer limiting, energy production resumes. Explain how the concentration of ATP increases with the availability of oxygen (detailed pathways and structures are NOT required). Next explain in detail how ATP is synthesized from ADP and Pi by the ATP synthase, focusing on the role of the β-subunits.

Answer 1

A) Out of the patway TCA cycle, electron transport chain, oxidative phosphorylation, β-oxidation for fatty acid degradation, ketone body metabolism, and lipid biosynthesis

TCA cycle

ETC

Oxidative phosphorylation

Beta oxidation

These pathways may be affected by low oxygen.

B) TCA-- mitochondria

ETC- mitochondria

Oxidative phosphorylation- mitochondria

Beta oxidation- mitochondria

C) ----during TCA cycle, oxidized equivalents ( NAD and FAD) are converted in to reduced form ( NADH and FADH2). For continuous operation of TCA cycle , these NAD and FAD must be continuously supplied. These are again reoxidized by ETC which is strictly aerobic in nature. ETC work only in presence of oxygen. If ETC will not work than NADH and FADH2 will not be re oxidized and TCA will stop due to unavailability to NAD and FAD. So that's why TCA is also aerobic.

-- ETC us strictly aerobic as its components cytochrome oxidase convert o2 in to water thus allow oxidation of reducing equivalents. In absence of oxygen, this process will not occur thus ETC is strictly aerobic.

- oxidative phosphorylation- both Oxidation and phosphorylation are coupled so in anaerobic conditions as ETC stops this will lead to stopping of phosphorylation as well

-- beta oxidation - this also requires NAD and FAD during the oxidation procedure. These are supplied via mitochondria ETC . In absence of oxygen, as ETC will not work , so no supply of NAD and FAD so no beta oxidation will occur.

4) as oxygen concentration increases or in presence of oxygen ETC will work and by process of oxidative phosphorylation, ATP will produce will simultaneous generation of NAD and FAD. These are utilized by TCA and beta oxidation cycles. Which again released energy in form of NADH and FADH2 and enter in to ETC and release energy in form of ATP.

5) ATP synthase Is complex V in ETC .

During oxidation of reducing equivalents, as electron ste passed through ETC complex some amount of energy is released. This energy is used to tranport protons from mitochondrial matrix in to intermembrane space . Thus cause intermembrane space to become acidic as compared to matrix and lead to generation of PMF ( proton motive force). As these H again reenter through complex V. There is generation of ATP.

ATP synthase complex is made up of two parts

F0 - act as channel, inserted in to membrane through which protons re enter in to mitochondria matrix

F1 - this is located in side to of mitochondria attached with F0 subunit. It is having 9 subunit.

3 alpha

3 beta

1 gamma

1 sigma

1 epsilon

Here beta subunit act as a catalytic subunit which exist in three forms open, loose and tight and by inter rotation lead to formation of ATP

Synthesis of ATP has been explained in attached image below