L24: ETC & Oxphos Flashcards
What is substrate-level phosphorylation?
- Involves enzymes and substrates that phosphorylate ATP
What is oxidative phosphorylation?
- Involves membrane-bound enzymes and proton gradient drives ATP phosphorylation.
What is the first step of oxphos?
- Electrons are delivered by high energy intermediates NADH and FADH2
- NADH is being oxidized to NAD+ (giving up 2 electrons to complex 1)
- Same process for FADH2 for complex 2
What is the ETC?
- The flow of electrons
What is step 2 of oxphos?
- energy is captured by electrons passed along the ETC in a step-down process
What does O2 have to do with oxphos?
- In aerobic cellular respiration: Oxygen is the terminal electron acceptor (TEA) & is reduced to water.
Which direction are protons (H+) pumped?
- Matrix to the intermembrane space
Step 3 of oxphos?
- Energy is needed to pump protons (H+) across the mitochondrial membrane.
Where does the energy to do the H+ (proton) transport come from?
- From ETC. Energy is captured by electrons donated to the protein complexes.
- The energy is from the electron transfer is released in a series of redox reactions.
Which direction do protons (H+) diffuse through the ATP synthase?
- Eukaryotic cells: Intermembrane space to the matrix
- Bacterial cells: Periplasm to the cytoplasm
Step 4 of oxphos?
- Protons flow through the ATP synthase which results in INDIRECT synthesis of ATP
ATP synthase transports H+ from the inter-membrane space to the matrix for ATP synthesis. what kind of transport is this?
- Facilitated diffusion
the energy from the movement of electrons through the electron-transport chain is used to move protons H+ from the matrix to the intermembrane space by…
- Active transport
In oxphos, ADP is phosphorylated with the aid of a proton (H+) gradient. this proton gradient provides…
- A source of energy to drive the ATP synthase
How does the indirect synthesis of ATP occur?
- protons flow through (passively) the ATP synthase
- this is called the proton motive force or proton gradient
- ATP is synthesized i.e. ADP is phosphorylated to ATP
What are the different depictions of ATP synthase?
- Lollipop shape (“Stem and head”)
- “Stem” proteins rotate as H+ diffuse through
- The flow protons provides the “head” proteins with energy to phosphorylate ADP to ATP
Which side of the membrane accumulates H+?
- Intermembrane space
Which side of the membrane synthesizes the ATP?
- Mitochondrial matrix
What is DNP?
- An effective weight-loss agent (drug)
What does DNP do?
- when the drug is added to mitochondria, the inner mitochondrial membrane becomes permeable (leaky) to protons
What is the effect of DNP on the proton (H+) gradient across the membrane?
- Proton gradient is lost
What is the effect of DNP on the ETC - will electron flow continue?
- yes, due to increased NADH
What is the effect of DNP on ATP synthesis?
- slows initially then stops (no H+ gradient)
What is the effect of DNP on energy - what happens to the energy generated from the proton motive force?
- It dissipates
What is the effect of DNP on oxygen consumption - will oxygen continue to be reduced to H2O?
- It increased
What is the effect of DNP on NADH/NAD+ ratio in the matrix
- remains the same (increase in total # of NADH due to increased catalysis of glucose)
DNP diet pills result in weight loss because…
- rate of glucose (sugar) catabolism increases
Oxidative phosphorylation general steps and principles.
- STEP 1: electrons are delivered by high energy intermediates NADH and FADH2
- STEP 2: energy is captured by electrons passed along the ETC in a step-down process
- STEP 3: this drives the energy needed to pump protons (H+) across the mitochondrial membrane
- STEP 4: protons flow through the ATP synthase results in INDIRECT synthesis of ATP
