mitochondria Flashcards
membrane DNA
always code mitochondrial proteins
The rest coded by nuclear DNA and imported
mtDNA
mtDNA is inherited cytoplasmically.
mtDNA is inherited maternally. Sperm has little to no cytoplasm.
Mitochondrial Membranes
- Outer membrane –smooth
- Inner membrane – has invaginations called cristae
- Intermembranous space between membranes
- Lumen within the inner membrane – matrix
- Matrix contains the mitochondrial DNA and mitochondrial ribosomes.
Fission
Mitochondrial Fission Factors (MFF).
– Recruit G-proteins (DRP-1) that hydrolyze GTP to constrict or pinch membranes
Fusion
Mitofusins (MFN).
– G-proteins that hydrolyze GTP to help membrane fusion.
– Different MFNs on outer and inner mito membrane.
– Mito fusion is a two step process: outer membrane fusion followed by inner membrane fusion
Mitochondrial Transport: Cargo
Folded proteins cannot undergo mitochondrial import
so they are left unfolded (uses ATP)
Translocons
two translocons
TOM - outer membrane
TIM - inner membrane
must pass through them both simultaneously
Import into mitochondrial matrix
- targeting signal recognises and directs
- passes through TOM and TIM unfolded
- during this, cargo is bound by matrix chaparone which pulls/directs it into matrix
- targeting sequence cleaved and folded
Oxidative Phosphorylation
Coupling a series of oxidation/reduction reactions (electron transport chain) with phosphorylation of ADP (ADP+ Pi) to generate ATP.
Goal is to efficiently convert energy stored in hydrocarbon (C-H) bonds of sugars (glucose) and lipids (fatty acids) in to ATP.
Linked with glycolysis and fatty acid metabolism in cytosol.
NAD and FAD
In biological systems, Nicotinamide adenine dinucleotide (NAD) and
flavin adenine dinucleotide (FAD) are high energy electron carriers.
Generating ATP (Stage 1: Sugar+Fat Metabolism)
Sugars and lipids are converted into intermediate molecules that are then transported into the mitochondrial matrix.
Glucose oxidised to pyruvate (Glycolysis). Generates some ATP and NADH in the process.
In order for fatty acids to be oxidised, first converted or “activated” with coenzyme A (Fatty acyl CoA)
Generating ATP (Stage 2: Giving up the electrons)
Pyruvate/Fatty acyl CoA oxidised to a common intermediate Acetyl CoA.
Electrons donated to electron carriers NAD+ and FAD to generate NADH and FADH2
Acetyl CoA is oxidised further in the Citric Acid Cycle (Krebs cycle) to generate more NADH and FADH2
Sugars and lipids eventually oxidised to CO2
Generating ATP (Stage 3: Pumping Protons)
NADH and FADH2 donate their electrons to a series of transmembrane inner membrane complexes.
Electrons are shuttled between complexes by mobile electron carriers.
Eventually electrons end up in O2 which is reduced to H2O.
Complex I, II and IV are also proton (H+) pumps.
Energy released from the passage of electrons through this chain is used to pump H+ from the matrix generating a proton and voltage gradient across inner membrane (-ve charge on matrix side).
Generating ATP (Stage 3: Pumping Protons)
NADH and FADH2 donate their electrons to a series of transmembrane inner membrane complexes.
Electrons are shuttled between complexes by mobile electron carriers.
Eventually electrons end up in O2 which is reduced to H2O.
Complex I, II and IV are also proton (H+) pumps.
Energy released from the passage of electrons through this chain is used to pump H+ from the matrix generating a proton and voltage gradient across inner membrane (-ve charge on matrix side).
Generating ATP (Stage 3: Pumping Protons)
NADH and FADH2 donate their electrons to a series of transmembrane inner membrane complexes.
Electrons are shuttled between complexes by mobile electron carriers.
Eventually electrons end up in O2 which is reduced to H2O.
Complex I, II and IV are also proton (H+) pumps.
Energy released from the passage of electrons through this chain is used to pump H+ from the matrix generating a proton and voltage gradient across inner membrane (-ve charge on matrix side).
