Electron Transport chain and oxidative phosphorylation Flashcards
DNP
- DNP inserts into the inner mitochondrial membrane
- shuttles protons between the intermembrane space and the matrix.
what happens when DNP is added to mitochondria
the inner mitochondrial membrane becomes permeable (leaky) to protons (H+).
why does DNP result in weight loss?
rate of glucose catabolism increases… and NOT turned into usable energy for the body!
effects of DNP addition to mitochondria on cellular respiration
- loss of H+ gradient across the membrane
- ETC continues due to the increase of NADH
- ATP synthesis slows initially then stops due to no H+ gradient
- increase in energy in the form of heat
- energy – proton motive force = dissipates
- increased oxygen consumption
- NADH/NAD+ ratio in the matrix remains the same (increase in total number of NADH due to increased catalysis of glucose)
where does OXPHOS occur in EUKARYOTES
in the mitocondria
Cellular Respiration Step 2, 3 in the matrix
Step 4 in the Inner Membrane
where does OXPHOS occur in BACTERIA
Cell’s plasma membrane
Steps 1, 2, and 3 of Cellular Respiration occur in the cytoplasm
Step 4 in the plasma membrane
general steps of OXPHOS
- Electrons are delivered by high energy intermediates NADH and FADH2.
- Energy is captured by electrons passed along the electron transport chain in step-down process.
- This drives the energy needed to pump protons (H+) across the mitochondrial membrane.
- Protons flow through the ATP synthase results in INDIRECT synthesis of
ATP
what leads to the generation of a proton electrochemical gradient and what does this do
oxidation of the electron carriers NADH and FADH2
proton electrochemical gradient becomes source of potential energy used to synthesize ATP
CHEMIOSMOTIC HYPOTHESIS
- protons in the intermembrane space diffuse down their electrical and concentration gradients through a transmembrane protein channel into the mitochrondrial matrix
- movement of protons through the channel is coupled with the synthesis of ATP
ATP synthase
enzyme composed ot 2 subunits:
* F0 and F1
* F0 forms the channel in the inner mitochondrial membrane through which protons flow
* F1 is the catalytic unit that synthesizes ATP
how does ATP synthase create ATP
- Proton flow through the F0 channel causes it to rotate
- converts the energy of the proton gradient into mechanical rotational energy… kinetic energy!!
- F0 rotations cause the F1 to rotation which then cause conformational changes that allow it to catalyze the synthesis of ATP from ADP and Pi
how are electrons delivered
by high energy intermediates NADH and FADH2
NADH is being oxidized to NAD+
i.e. gives up 2 electrons to complex I. Ditto for FADH2 to complex II!
terminal electron acceptor
Oxygen accepts the electrons at the end of the chain – called Terminal Electron Acceptor (TEA) & is reduced to water.
active transport in OXPHOS?
- Energy is needed to pump protons (H+) across the mitochondrial membrane.
H+ movement from matrix to intermembrane space requires energy
i.e. active transport
Where does the energy to do the H+ transport come from?
- From ETC !
- Energy is captured by electrons donated to the Protein complexes!
- the energy from the transfer of electrons is released in a series of redox reactions.
- The energy is used to pump H+ (protons) from the mitochondrial matrix into the intermembrane space.
