ETC Flashcards
ETC
Electron transport chain
Where does ETC occur?
In mitochondria
Where exactly does ETC take place?
In between the double membrane of a mitochondrion. Intermembrane space is involved, as well as inner mitochondrial membrane (cristae)
What is the role of NADH and FADH2 in ETC?
NADH and FADH₂ donate electrons to the ETC, which generates a proton (H⁺) gradient across the membrane.
What is ETC? What happens during ETC? (4 steps)
Process:
1. Electron carriers (NADH, FADH₂) donate electrons to protein complexes (Complex I, II, III, IV). 2. Protons (H⁺) are pumped across the membrane, creating a proton gradient. 3. ATP Synthase. Protons flow back through ATP synthase, driving the phosphorylation of ADP to ATP. 4. Oxygen acts as the final electron acceptor, combining with electrons and protons to form water.
What is the final election acceptor in ETC?
Oxygen
What is a proton gradient in ETC?
A proton gradient refers to a difference in proton concentration across a membrane.
It is typically created during the electron transport chain in cellular respiration. The proton gradient plays a key role in the formation of ATP through a process known as chemiosmosis.
What is chemiosmosis?
Chemiosmosis is the process of diffusion of ions (usually H+ ions, also known as protons) across a selectively permeable membrane. As in osmosis, chemiosmosis leads to a concentration gradient of the diffusing ion across the membrane.
Phosphorylation is
Addition of phosphorus
Fx ADP tp ATP in ETCs last step
Net Gain in ETC
Theoretical yield of 30-32 ATP per glucose molecule (ideal conditions).
TF
ETC is an aerobic process
True; uses Oxygen
Why are foldings of mitochondrial inner membrane (cristae) important?
To increase the capacity of the mitochondrion to synthesize ATP, the inner membrane is folded to form cristae.
These folds allow a much greater amount of electron transport chain enzymes and ATP synthase to be packed into the mitochondrion.
What protein complexes take part in ETC? How many are there and what roles do each one have?
The ETC consists of four primary complexes:
Complex I
(NADH: ubiquinone oxidoreductase), Complex II
(succinate: ubiquinone oxidoreductase),
Complex III
(cytochrome bc1 complex),
Complex IV
(cytochrome c oxidase).
Additionally, ATP synthase (Complex V) is involved in the final stage of ATP production.
The associated electron transport chain is NADH → Complex I → Q → Complex III → cytochrome c → Complex IV → O2 where Complexes I, III and IV are proton pumps, while Q and cytochrome c are mobile electron carriers.
Nice definition for etc and cristae and proteins
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.
Draw etc
Now!
What does complex 1 do?
Complex I (NADH Dehydrogenase):
Input: NADH from the Krebs cycle donates electrons (e⁻).
Process:
NADH is oxidized to NAD⁺, releasing electrons.
These electrons are transferred to ubiquinone (Q) via iron-sulfur clusters.
Energy released pumps H⁺ protons from the mitochondrial matrix into the intermembrane space.
Effect: Establishes a proton gradient.
What does complex 2 do?
Complex II (Succinate Dehydrogenase):
Input: FADH₂ (produced in the Krebs cycle) donates electrons.
Process:
FADH₂ is oxidized to FAD, transferring electrons directly to ubiquinone (Q).
No protons are pumped at this step, so FADH₂ contributes less to ATP production compared to NADH.
What is Q?
Ubiquinone (Q):
A mobile electron carrier that shuttles electrons from Complex I and Complex II to Complex III.
What does complex 3 do?
Complex III (Cytochrome bc₁ Complex):
Process:
Electrons from ubiquinone (Q) are transferred to cytochrome c, another mobile electron carrier.
Energy released pumps more H⁺ protons into the intermembrane space.
What is Cytochrome c?
Cytochrome c:
A small, mobile protein that carries electrons from Complex III to Complex IV.
What does complex 4 do?
Complex IV (Cytochrome c Oxidase):
Input: Electrons from cytochrome c.
Process:
Electrons are transferred to the final electron acceptor, oxygen (O₂).
O₂ combines with H⁺ protons to form water (H₂O).
This is why oxygen is essential for aerobic respiration.
ATP Synthase
ATP Synthase (Complex V):
Process:
The proton gradient created by the complexes allows H⁺ protons to flow back into the mitochondrial matrix through ATP synthase.
This flow drives the production of ATP from ADP and inorganic phosphate (Pi).
Oxidative phosphorylation
Oxidative phosphorylation is the production of ATP using the energy released by electrons as they move through the electron transport chain and the energy stored in the proton gradient (chemiosmosis). It occurs in the mitochondria and is the final, energy-producing step of cellular respiration.
What is Pi?
Inorganic phosphate
Whai is the net ATP Production of oxidative phosphorylation?
Around 30-32 ATP molecules per glucose molecule.
