Lecture 12: Mitochondria Flashcards
When was the theory of symbiogenesis thought of allegedly?
1905
Who allegedly thought of the idea of symbiogenesis?
Konstantin Mereschkowski
Which cell in the body has the most mitochondria?
Liver cells
Which cell in the body has the least mitochondria?
Red Blood Cell
Describe the membrane structure of Mitochondria
Double membrane structure with an outer and inner layer.
The outer membrane is smooth whilst the inner layer is highly folded into cristae. This is to increase surface area
Where is the mitochondrial matrix located?
In the inner membrane
What does the mitochondrial matrix have?
Enzymes that are involved in the citric acid cycle and the conversion of pyruvate to acetyl-CoA which are important steps in ATP production
What do mitochondria contain their own of?
Contains its own DNA and ribosomes, allowing them to synthesise some of their own proteins and replicate independently of the cell
I’m gonna use this acronym OMM, what does it mean?
Outer mitochondrial membrane
ToD: The OMM is semi-permeable?
True
What is the OMM made out of?
Lipids
Proteins
Porins
Describe the role of Porins in the OMM
Forms large channels that allow the passage of molecules (up to a certain size) in and out of the mitochondria
What is the role of the OMM? (3)
Separates the contents of the mitochondria from the cytosol of the cell
Regulates the exchange of metabolites, ions and proteins between the mitochondria and the cytoplasm
Plays a role in mitochondrial fission and fusion
Initiates apoptosis
Name two receptors involved in the import of proteins/metabolites into the mitochondria
Voltage-dependent anion channel (VDAC)
Translocase of the outer membrane (TOM)
How does the outer membrane initiate apoptosis?
Releases pro-apoptotic proteins such as cytochrome c
Where are the pro-apoptotic proteins stored in the mitochondria?
The intermembrane space
How many genes does the mitochondrial genome code?
37
How are mitochondria inherited?
Exclusively maternal
How many protein-coding regions are there in the mitochondrial genome?
13
How many tRNA genes are there in the mitochondrial genome?
22
What is the total length of the mitochondrial genome in terms of base pairs?
16,569
What is a protein translocator (in the mitochondrial context)?
A complex of proteins
What is the role of a protein translocator? (2)
Maintains the function and integrity of mitochondria
Responsible for the import of proteins into the mitochondria as well as the proper insertion of these proteins into the mitochondrial membranes.
What is the role of the TOM complex?
Imports nucleus-encoded mitochondrial precursor proteins into the intermembrane space
What proteins are the SAM complex made of?
B-barrel proteins
Where is the SAM complex found?
Common in the outer membrane
What is the role of the TIM23 complex? (2)
Transports some of the proteins into the matrix, while helping to insert transmembrane proteins into the inner membrane
What is the role of the TIM22 complex? (1)
Mediates the insertion of a sub-class of inner membrane proteins
e.g carrier proteins for ADP, ATP and Pi
What is the role of the OXA complex?
Mediates the insertion of inner membrane proteins that are synthesised in the mitochondrion
Proteins destined for the mitochondrial matrix are first synthesised where?
Cytosolic ribosomes
What is the name of the protein that cytosolic ribosomes make for the mitochondrial matrix?
Precursor proteins
What do precursor proteins have to direct them to the mitochondria?
N-terminal mitochondrial targeting sequence (MTS)
What recognises the precursor proteins on the outer membrane?
Translocase of the outer membrane (TOM) complex
How do the precursor proteins make it through the outer mitochondrial membrane
The TOM complex forms a protein-conducting channel
After the precursor protein has passed through the TOM complex, where is it transferred next?
The inner membrane (TIM) complex on the inner mitochondrial membrane.
This forms a second protein-conducting channel that allows the precursor protein to cross the inner membrane
What binds to the precursor protein in the mitochondrial matrix and assists in its folding and assembly?
The mitochondrial matrix-localised chaperones (Heat shock protein 70)
Co-chaperones
What section of the protein needs to be cleaved off to mature the protein?
Mitochondrial Targeting Sequence
Name the two peptidases needed to cleave the protein
Mitochondrial Processing Peptidase (MPP)
Mitochondrial Intermediate Peptidase (MIP)
Where is the mature protein released into during the final stage?
Mitochondrial matrix
