OXIDATIVE PHOSPHORYLATION STUDY QUESTIONS AND SOLUTIONS
Electron transport chain and oxidative phosphorylation
As it turns out, the reason you need oxygen is so your cells can use this
molecule during oxidative phosphorylation, the final stage of cellular
respiration. Oxidative phosphorylation is made up of two closely connected
components: the electron transport chain and chemiosmosis. In the electron
transport chain, electrons are passed from one molecule to another, and energy
released in these electron transfers is used to form an electrochemical gradient.
In chemiosmosis, the energy stored in the gradient is used to make ATP.
The electron transport chain is a series of proteins and organic molecules found
in the inner membrane of the mitochondria. Electrons are passed from one
member of the transport chain to another in a series of redox reactions. Energy
released in these reactions is captured as a proton gradient, which is then used to
make ATP in a process called chemiosmosis. Together, the electron transport
chain and chemiosmosis make up oxidative phosphorylation. The key steps of
this process, shown in simplified form in the diagram above, include:
Electron transfer in the mitochondria
The electron transport chain is a collection of membrane-embedded proteins and
organic molecules, most of them organized into four large complexes labeled I
to IV. In eukaryotes, many copies of these molecules are found in the inner
mitochondrial membrane. In prokaryotes, the electron transport chain
components are found in the plasma membrane.
As the electrons travel through the chain, they go from a higher to a lower
energy level, moving from less electron-hungry to more electron-hungry
molecules. Energy is released in these "downhill" electron transfers, and several
of the protein complexes use the released energy to pump protons from the
mitochondrial matrix to the intermembrane space, forming a proton gradient.
All of the electrons that enter the transport chain come from NADH and
FADH2 molecules produced during earlier stages of cellular respiration:
glycolysis, pyruvate oxidation, and the citric acid cycle.
Electron transport chain and oxidative phosphorylation
As it turns out, the reason you need oxygen is so your cells can use this
molecule during oxidative phosphorylation, the final stage of cellular
respiration. Oxidative phosphorylation is made up of two closely connected
components: the electron transport chain and chemiosmosis. In the electron
transport chain, electrons are passed from one molecule to another, and energy
released in these electron transfers is used to form an electrochemical gradient.
In chemiosmosis, the energy stored in the gradient is used to make ATP.
The electron transport chain is a series of proteins and organic molecules found
in the inner membrane of the mitochondria. Electrons are passed from one
member of the transport chain to another in a series of redox reactions. Energy
released in these reactions is captured as a proton gradient, which is then used to
make ATP in a process called chemiosmosis. Together, the electron transport
chain and chemiosmosis make up oxidative phosphorylation. The key steps of
this process, shown in simplified form in the diagram above, include:
Electron transfer in the mitochondria
The electron transport chain is a collection of membrane-embedded proteins and
organic molecules, most of them organized into four large complexes labeled I
to IV. In eukaryotes, many copies of these molecules are found in the inner
mitochondrial membrane. In prokaryotes, the electron transport chain
components are found in the plasma membrane.
As the electrons travel through the chain, they go from a higher to a lower
energy level, moving from less electron-hungry to more electron-hungry
molecules. Energy is released in these "downhill" electron transfers, and several
of the protein complexes use the released energy to pump protons from the
mitochondrial matrix to the intermembrane space, forming a proton gradient.
All of the electrons that enter the transport chain come from NADH and
FADH2 molecules produced during earlier stages of cellular respiration:
glycolysis, pyruvate oxidation, and the citric acid cycle.
