Everything about Proton Pump totally explained
A
proton pump is an
integral membrane protein that's capable of moving
protons across the
membrane of a
cell,
mitochondrion, or other subcellular compartment.
Function
In
cell respiration, the pumps grab protons from the
matrix, the space between the two enclosing membranes of the
organelle, and release the protons within the inner membrane. The confined protons create a difference or
gradient in both
pH and
electric charge (ignoring differences in
buffer capacity) and establish an
electrochemical potential that acts as a kind of battery or reservoir of stored energy for the cell. The inner cell membrane functions in a similar way to a dam in a river. It blocks protons from drifting back into the matrix. Since the pumping action is against the gradient, it requires
work (energy). The process is directly analogous to bicycling uphill or charging a battery (storing up
potential energy). It is important to remember that the proton pump doesn't create energy. Instead, the gradient stores energy for the appropriate time.
Mobility
Some of the enzymes involved in the
electron transport chain, such as
ubiquinone, travel along the matrix, like freight boats, navigating up and down the river.
Others such as
NADH-Q
reductase, act like ferryboats and cross the matrix. Enzymes that can cross the matrix may have a secondary role as proton pumps because they can deliver protons to the inner membrane.
Diversity
In humans
In
mitochondria,
reducing equivalents provided by
electron transfer or
photosynthesis power this translocation of protons. For example, the translocation of protons by
cytochrome c oxidase is powered by reducing equivalents provided by reduced
cytochrome c. In the
plasma membrane proton ATPase and in the
ATPase proton pumps of other cellular membranes, ATP itself powers this transport.
The F
oF
1 ATP synthase of mitochondria, in contrast, usually conduct protons from high to low concentration across the membrane while drawing energy from this flow to synthesize ATP. To allow the passage of protons a
proton channel temporarily opens in the inner membrane.
Non-humans
In
bacteria and other ATP-producing organelles than mitochondria, ATP-producing organelles,
reducing equivalents provided by
electron transfer or
photosynthesis power the translocation of protons.
CF
1 ATP
ligase of
chloroplasts correspond to the human F
oF
1 ATP synthase in plants.
Bacteriorhodopsin is a
photosynthetic pigment used by
archaea, most notably
halobacteria.
Further Information
Get more info on 'Proton Pump'.
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