Mitochondrial structure and function Flashcards
What is the structure of the Mitochondrial DNA (mtDNA)?
Covalently-closed DNA molecule (16.6 kb).
Where is the Mitochondrial DNA (mtDNA)?
Located in mitochondrial matrix.
How much Mitochondrial DNA (mtDNA) is in the cell?
Multiple copies per cell
What is the make-up of Mitochondrial DNA (mtDNA)?
- 13 protein-encoding genes
- 2 rRNAs
- 22 tRNAs
What is glycolysis?
Glucose is broken down into pyruvate.
What does the krebs cycle produces?
FADH2 and NADH.
What is the function of FADH and NADH?
Carry the electrons needed for respiration.
Draw the process of beta-oxidation of fatty acids.
What is the OXPHOS process split into?
Electron transport chain. ( complex1-4)
What happens during the OXPHOS process?
Protons are donated by the NADH and the FADH which drives a proton gradient to travel across the matrix to the intermembrane space creating an electrochemical gradient. ATP synthase allows the protein to flow back and create ATP.
Which OXPHOS enzyme is the largest?
Complex 1
What is the structure of complex 1?
Has a hydrophobic arm (protrudes into the mitochondrial matrix) and a hydrophilic arm (sits within the mitochondrial membrane).
How many subunits does complex 1 contain?
45
How many subunits in complex 1 is encoded by mitochondria DNA?
7
How many subunits are encoded by nuclear DNA?
38
What is the function of complex 1?
The first entry point for electrons into the TCA cycle, NADH is oxidised, and electrons are passed through sulphur clusters until it reaches ubiquinone.
What happen during the reactions occur at complex 1?
Protons pumped into the intermembrane space.
What is Q?
Coenzyme.
What is QH2?
Reduced CoQ or Ubiquinol.
What is the net transfer of protons during the reactions in complex 1?
4 protons from the inside to the outside. contributes to electrochemical gradient.
What is the name for complex 2?
Succinate dehydrogenase.
Which of the complexes in the OXPHOS cycle are the smallest/
Complex 2
How many subunits is complex 2 made up of?
4.
What subunits is complex 2 or succinate dehydrogenase made up of?
SDH (A,D,C AND D).
What kind of DNA encodes for complex 2?
Nuclear, no mitochondrial.
What is unique about complex 2?
Takes part in both the krebs cycle and the electron transport chain.
Where is SDHA?
Hydrophilic so it is inside the matrix.
Where is SDHB?
Hydrophilic so it is inside the matrix.
Where is SDHC?
Hydrophobic so integral membrane proteins.
Where is SDHC?
Hydrophobic so integral membrane proteins.
Where is SDHD?
Hydrophobic so integral membrane proteins.
What is the function of complex 2?
Catalyses the oxidation of succinate to fumarate.
How does the complex 2 oxidate succinate?
FAD is reduced.
Electrons from FADH2 transferred to ubiquinone via the iron sulphur clusters in SDHB reducing it.
QH2 passes electrons to carriers.
What is the net proton transfer of complex 2?
0, doesn’t contribute to the electrochemical gradient at all.
What is the name of complex 3?
Ubiquinol : cytochrome C oxidoreductase
How many monomers is complex 3 made up of?
2 it is a functional dimer.
How many subunits does each of the monomers in complex 3 have?
11.
How many subunits are encoded by mitochondial DNA?
1 per monomer, the rest is nuclear DNA.
What is the function of complex 3?
It goes through the q cycle.
What is the Q cycle?
In the first half cycle, the ubiquinol molecule attaches on to complex 3 one electron transfers to the iron sulphur cluster and the other attaches to cytochrome 3 this forms a quinol radical.
In the other half cycle, another molecule of ubiquinol follows the pathway
What is the result of the Q cycle?
The oxidation of ubiquinol (QH2) to ubiquinone (Q)
The reduction of cytochrome c.
How many subunits does complex 4 contain?
14
Which subunits in complex 4 are encoded by the mitochondrial DNA?
1 to 3
Which subunits in complex 4 are encoded by the nuclear DNA?
4- 14
What does Compex 4 contain?
2 non-covalently bound haem and copper centres for electron transfer.
What is the function of complex 4?
Electron transfer.
How does complex 4 transfer electrons?
Oxidation of 4 molecules of cytochrome c
The passes the electrons to copper centres
Then passes to iron sulphur clusters and reduces oxygen to water.
What is the net transfer in complex 4?
4 protons being pumped and 2 molecules of water being made.
What is complex 5 also known as?
ATP synthase.
How many subunits does complex 5 have?
16
How many of the complex 5 subunits are encoded by mitochondrial DNA?
2, the other 14 are nuclear.
What are the 2 main domains present in complex 5?
Fo domain
F1 domain.
What is the f0 domain?
Contains proton channel, additional subunits and C ring subunits
What is the f1 domain?
- active site for ATP synthesis
- protrudes into the matrix
What is classed as the central stalk within the f1 domain in complex 5?
One γ, ᵯ , and ᵰ subunits
What is classed as the peripheral stalk within the f1 domain in complex 5?
Subunits b, d, F6 and OSCP
What is the function of complex 5 (ATP synthase)?
Harness energy stored in proton gradient.
How does ATP synthase (complex 5)?
Together, the c-ring and additional subunits create a proton channel.
Protons move across the inner mitochondrial membrane down the electrochemical gradient.
Protons enter the F0 sub-complex.
As the protons cause rotation of the c-ring
Central stalk rotates
This results in conformational changes that enable the access of ADP + Pi and the release of the ATP.
