Transport into mitochondria & peroxisomes Flashcards
What is the primary function of the mitochondria?
Produce H+ gradient across inner membrane, which drives the ATPase, which produces ATP.
What is the first step in the mitochondria producing ATP?
Glycolysis - the breakdown of glucose in pyruvate occurs in the cytoplasm.
What happens when the pyruvate enters the mitochondria?
Decarboxylation
Describe the 2 membranes in the mitochondria
Outer membrane - encloses the organelle.
Inner membrane - highly folded (high SA). These folds are known as cristae.
What does the inner matrix contain?
The enzymes responsible for energy production
Why is the outer membrane being perforated (large channels - porins) beneficial?
Allows entry of molecules <5000 kDa
What type of enzymes are present in the outer membrane?
Enzymes involved in mitochondrial lipid synthesis
What enzymes are present in the inter membrane space?
Enzymes that use ATP to phosphorylate other nucleotides
What enzymes are present in the mitochondrial matrix?
Enzymes involved in the Krebs cycle
What is contained in the mitochondrial matrix?
- mitochondrial DNA
- ribosomes
- tRNAs & rRNAs
- enzymes
- metabolites
Describe the mitochondrial genome
- circular chromosome (double-stranded)
- 15-17 Kbps (kilo base pairs)
- encodes 37 genes
- the mitochondrial DNA is inherited from the mother.
Describe the process of how undesirable chemicals produced as a by-product of metabolism in the mitochondria
the debris is separated to one side of mitochondria. Fission then occurs, with one half staying healthy. The smaller & damaged mitochondria can then be targeted and an autophagosome is created.
How does mitochondria create more ATP in emergency situation?
healthy mitochondria fuses with damaged mitochondria to create more ATP (fussion).
Where are mitochondria synthesized from?
new mitochondria must arise from existing mitochondria
How does the cell regulate the level of mitochondria present?
Balances the dynamic flux between fission & fusion
What translocation proteins embedded into the mitochondrial membranes are used to transport proteins into mitochondria (which 3 complexes)?
TOM - Translocator of the Outer Membrane
TIM - Translocator of the Inner Membrane
SAM - Sorting & Assembly Machinery
What complex allows the movement of a protein once it docks on a receptor?
TIM23 complex
How do the proteins manage to fit into the mitochondria?
the proteins UNFOLD before docking with the TOM complex
Why are chaperones useful in transporting proteins into the mitochondria?
chaperones bind to peptides, as they are made & control how they fold
What do chaperones need to dissociate from the polypeptide chain?
ATP
What is the end result of the electrochemical H+ gradient driven by electron transport?
ATP production
How do proteins enter the OUTER membrane?
through porins (beta-barrel proteins)
What is the solution, as TOM cannot insert proteins into bilayer?
The proteins are kept unfolded by chaperones.
How do you get a soluble protein in the inter membrane space?
You cleave after membrane insertion
Are there different pathways depending on what is being transported?
YES
How many membranes are present in peroxisomes?
1
Are there DNA or ribosomes in peroxisomes?
NO
Where are peroxisomes?
in eukaryotic cells
What is the function of peroxisomes?
Contains a variety of oxidative enzymes which remove hydrogen atoms from various organic compounds.
What is the reaction that peroxisomes use to remove Hydrogen atoms?
RH2 + O2 –> R + H2O2
What role does the peroxisomes play in the liver?
- detoxification
- processing of alcohol
- oxidation of fatty acids (breaking down fat)
Where are peroxisomal membrane proteins made?
cytoskeleton - then insert into the membrane of pre-existing peroxisomes
How are peroxisomes created?
peroxisomes arise from pre-existing ones, by organelle growth & fission - like mitochondria
How do proteins get into peroxisomes?
Peroxins (using ATP) form a trans locator in the membrane. Pex5 recognises signal sequences & accompanies cargo into peroxisomes.
