Cell Death Pathways Flashcards
How many copied of covalently-closed double-stranded DNA does each mitochondria contain?
2-10
Why is the nuclear genome also required for mitochondria?
As the mitochondria has limited coding capacity for mtDNA and still required proteins encoded by the nuclear genome.
Is mitochondria paternally or maternally inherited?
Maternally
How many mitochondria are there per cell?
100-1000
Describe the structure of a mitochondria?
Has a matrix which is highly concentrated with hundred of enzymes, inner membrane is folded into cristae and contains the protein required to carry out ATP synthesis, outer membrane contains a large channel forming protein called porin, the inter-membrane space contains several enzymes that use the ATP passing out of the matrix to phosphorylate other nucleotides.
What size molecules are porins permeable to?
5000 dalton or less
What is protein translocation?
The process of moving proteins into the mitochondria or other organelles.
What does protein translocation into the mitochondria require?
A N-terminal uptake targeting or transit-sequence. They are often rich in basic amino acids, serine and threonine.
How are proteins translocated into the mitochondria?
First synthesised in the cytosol as mitochondrial precursor proteins and within seconds/minutes are post-translational translocated and a signal sequence directs the protein to a specific sub-compartment.
What signal sequences are used for directing mitochondrial proteins to the matrix and why is this different?
An amphiphillic alpha helix at the N-terminal. They are rapidly removed by peptidase unlike the remaining signals sequences on other mitochondrial proteins.
Describe protein translocators?
Multi-subunit protein complexes.
TOM complex transfers proteins across the outer membrane and TIM22/23 transfer proteins across the inner membrane. Can work together to pass the proteins across both membrane simultaneously.
Different subunits for recognition and translocation.
What do interacting protein allow for?
The mitochondrial precursor proteins to remain unfolded in the cytosol and prevent aggregation/folding before interaction with TOM.
What are interacting proteins?
Some are chaperone proteins, others are specific for the precursor protein and bind directly to the signal sequence. They bind until the precursor protein associates with TOM then they are stripped.
Why are diseases on mitochondria common?
High mutation rate in mtDNA
What are mitochondrial diseases often?
Neuromuscular, rare in children and currently un-curable.
