MCB Lecture 14, Oxidative Phosphorylation Flashcards
Describe the overall process of the electron transport chain
- NADH docks at Complex I and is converted to NAD+, releasing 2e-
The electrons move through Complex 1 on the FMN and Fe-S clusters
Electrons reduce Ubiquinone to Ubiquinol
Q -> QH2 - Ubiquinol diffuses through the membrane (lipophilic) to Complex III.
4 H+ protons are pumped from the matrix to the intermembrane space per NADH at complex I - Coenzyme Q : Ubiquinone. Is reduced by electrons from NADH at CI and electrons from FADH2 from CII
- Complex II is also known as succinate dehydrogenase.
Here, succinate docks and is turned into fumarate, generating FADH2.
Electrons from FADH2 -> Fe-S -> Q -> QH2. - Complex III has a cavern with a ubiquinol docking site. The electrons end up on cytochrome C.
4 protons are pumped (per 1 NADH) - Cytochrome C shuttles electrons from CIII to CIV.
the Fe3+ centre of the heme C prosthetic group accepts the electrons - Complex IV has a docking station for cytochrome C.
The electrons from cyt. c move through various groups are accepted by O2.
2 H+ are pumped into IMS and four H+ are used in the reduction of O2 -> H2O - This sets up a Chemiosmotic gradient: there are many protons in the intermembrane space that want to diffuse back.
At ATP synthase, protons diffuse through the F0 subunit, causing the gamma- subunit of F1 to rotate.
This allows the normally unfavourable reaction ADP + Pi -> ATP to happen
What are all the compounds we have got from Glycolysis, PDH complex, TCA cycle?
Glycolysis: net 2 ATP, 2 NADH
PDH: 2 NADH
TCA cycle: 6 NADH, 2 FADH2, 2 GTP
Describe the structure of Complex I
Large L shaped protein with 42 subunits
A FMN-containing flavoprotein
6 Fe-S clusters
A N-2 iron sulfur protein
Describe the structure of Complex II
4 protein subunits: A, B, C, D
A and B are in the matrix
C and D are transmembrane
Contains two types of prosthetic groups:
A-B: Fe-S clusters, FAD, Succinate binding site
C-D: heme group: heme b and Q binding site
Describe the structure of Complex III
Three subunits:
1. Cytochrome B
Two cyt B subunits form a cavern
Caven: Qn and Qp binding sites
Coenzyme Q moves from matrix (Qn) to IMS (Qp)
- Rieske Iron-Sulfur proteins
- Cytochrome C
Describe the structure of Complex IV
4 core subunits
Subunit I
Two heme groups (a and ac)
Copper ion (Cub)
Subunit II
2 copper ions Cua
Cyt c binding site
Subunit III
Essential for H+ movement
Subunit IV
Unknown role, but pumps 2H+
Describe the characteristics of Coenzyme Q
Lipophilic molecule
What are the two forms of coenzyme Q, and what are their names?
Ubiquinone: Q, oxidised
Ubiquinol: QH2, reduced
Describe the structure of Cytochrome C
Protein Prosthetic group (heme c) with iron centre
What is the function of coenzyme Q?
Shuttles electrons from Complex I and Complex II to Complex III, where the electrons are transferred to cytochrome c
What is the function of cytochrome C?
Transfers electrons between complex III and IV
Which complexes pump protons into the intermembrane space?
Complex I, complex III and complex IV
Which complex also has a role in the TCA cycle?
Complex II is also known as succinate dehydrogenase
Describe the structure of ATP Synthase
F0 stalk and F1 head
F0:
A, B2, C10
F1:
alpha3, beta 3, gamma, delta, epsilon
The head has 3 alpha-beta dimers is a ring. These have different adenine binding sites.
i. Beta-empty
ii. Beta-ADP
iii. Beta-ATP
Describe how rotational catalysis works
When protons move through the stalk, the gamma subunit of F1 rotates.
This rotation makes the normally unfavourable reaction ADP + Pi -> ATP occur.
The formed ATP molecules is then released
