Bio – week 7 – lecture 2 – 2/5/25 – Oxidative Phosphorylation:
Oxidative phosphorylation: Combination of electron transport chain & chemiosmosis
The electron transport chain:
- Electrons are donated by the carriers
(NADH and FADH2)
- Electrons “fall” towards ever-more
electronegative e partners within the
inner membrane of the
mitochondria, becoming less and less
energetic.
- The energy the electrons release can
be harvested to pump H+ from one
compartment into another
compartment across a membrane ->
creates potential energy and
eventually makes ATP.
- The final electron acceptor (the most
electronegative of all) is oxygen.
Summary: controlled combination of H+ with electron and oxygen to give us water.
The electron transport chain – More in-depth:
Left photo: y-axis = gibs free energy (energy available to do work)
it starts from high energy of free energy and ends with low level of
free energy.
1) NADH and FADH2 donate electrons -> once donated NADH
is being re-oxidised into NAD+ and FADH2 is re-oxidised to
FAD. We re-oxidise the electron carriers as they donate
their electrons at the start.
2) All the middle electronegative partners are the Cyt (goes
from least electronegative to most electronegative
meaning the ones at the end want the electrons the most)
leads to the most electronegative which is O2 which can be
reduced to H2O -> chain of electronegative partners which
pass the electron down the chain from one to the next. (at
each step each electron looses a little bit of its energy and
that can be harvested to do work).
, Right photo: The more crucial photo to understand
The re-oxidation of NAHD -> NAD+ and FADH2 -> FAD is crucial because it replenishes
our stores of electron acceptors so they can go back and do their job again.
- All occurs in matrix and inner membrane of the mitochondria.
- Yellow line is the electrons (lose energy at each step or each transfer) – series of
giving and accepting electrons called a series of oxide-reduction (it is a long chain of
redox reactions) – whole principle is a series of redox reactions – electrons loose
little bit sof energy at each transfer this energy is used to do work such as pumping
H+ from one compartment (the matrix) into another compartment (intermembrane
space) – pumping can happen at complex 1 (I), 3 (III), and 4 (IV) – pumping creates a
gradient of concentration of H+ (more H+ in intermembrane - top section than in the
matrix - bottom section) – important as a gradient concentration is a form of
potential energy its something that is stored there
- once H+ gradient is established thanks to electron transport chain the ATP synthase
can use the existing potential energy from the gradient of concentration and
facilitate the passing down the concentration gradient of H+ high -> low through the
ATP synthase – when the H+ flow through it can make the ATP synthase spin on itself
and allow you to do more work and transform a lot of ADP into a lot of ATP –
estimated that every 3-4 H+ makes one ATP.
- It is called chemiosmosis -> osmosis is the movement of water and this is the same
idea but its not water that is moving it is H+ (chemical) therefore called
chemiosmosis. (same as osmosis flows from high -> low concentration)
The combination of the electron transport chain, which is a series of redox reactions and
chemiosmosis, which is a way of making ATP is called together = Oxidative
phosphorylation
The electron transport chain: Overall Key ideas (good for revision)
- Electrons are donated by NADH and FADH2
Oxidative phosphorylation: Combination of electron transport chain & chemiosmosis
The electron transport chain:
- Electrons are donated by the carriers
(NADH and FADH2)
- Electrons “fall” towards ever-more
electronegative e partners within the
inner membrane of the
mitochondria, becoming less and less
energetic.
- The energy the electrons release can
be harvested to pump H+ from one
compartment into another
compartment across a membrane ->
creates potential energy and
eventually makes ATP.
- The final electron acceptor (the most
electronegative of all) is oxygen.
Summary: controlled combination of H+ with electron and oxygen to give us water.
The electron transport chain – More in-depth:
Left photo: y-axis = gibs free energy (energy available to do work)
it starts from high energy of free energy and ends with low level of
free energy.
1) NADH and FADH2 donate electrons -> once donated NADH
is being re-oxidised into NAD+ and FADH2 is re-oxidised to
FAD. We re-oxidise the electron carriers as they donate
their electrons at the start.
2) All the middle electronegative partners are the Cyt (goes
from least electronegative to most electronegative
meaning the ones at the end want the electrons the most)
leads to the most electronegative which is O2 which can be
reduced to H2O -> chain of electronegative partners which
pass the electron down the chain from one to the next. (at
each step each electron looses a little bit of its energy and
that can be harvested to do work).
, Right photo: The more crucial photo to understand
The re-oxidation of NAHD -> NAD+ and FADH2 -> FAD is crucial because it replenishes
our stores of electron acceptors so they can go back and do their job again.
- All occurs in matrix and inner membrane of the mitochondria.
- Yellow line is the electrons (lose energy at each step or each transfer) – series of
giving and accepting electrons called a series of oxide-reduction (it is a long chain of
redox reactions) – whole principle is a series of redox reactions – electrons loose
little bit sof energy at each transfer this energy is used to do work such as pumping
H+ from one compartment (the matrix) into another compartment (intermembrane
space) – pumping can happen at complex 1 (I), 3 (III), and 4 (IV) – pumping creates a
gradient of concentration of H+ (more H+ in intermembrane - top section than in the
matrix - bottom section) – important as a gradient concentration is a form of
potential energy its something that is stored there
- once H+ gradient is established thanks to electron transport chain the ATP synthase
can use the existing potential energy from the gradient of concentration and
facilitate the passing down the concentration gradient of H+ high -> low through the
ATP synthase – when the H+ flow through it can make the ATP synthase spin on itself
and allow you to do more work and transform a lot of ADP into a lot of ATP –
estimated that every 3-4 H+ makes one ATP.
- It is called chemiosmosis -> osmosis is the movement of water and this is the same
idea but its not water that is moving it is H+ (chemical) therefore called
chemiosmosis. (same as osmosis flows from high -> low concentration)
The combination of the electron transport chain, which is a series of redox reactions and
chemiosmosis, which is a way of making ATP is called together = Oxidative
phosphorylation
The electron transport chain: Overall Key ideas (good for revision)
- Electrons are donated by NADH and FADH2
