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Session #70: Mitochondria and Peroxisomes
Terms in this set (76)
An organelle found in large numbers in most cells, in which the biochemical processes of respiration and energy production occur.
What is the structure of mitochondria?
1. Outer Membrane
2. Inner Membrane (cristae)
3. Intermembrane Space
Outer Membrane (Mitochondria)
- The most outer membrane of the mitochondria
- Highly permeable to small molecules
- Involved with lipid synthesis
Inner Membrane (Mitochondria)
- Surrounds the matrix and is folded into
- Contains the oxidative phosphorylation proteins (complex 1, 3, 4, and 5)
- Also contains ATP synthase which pumps protons into the intermembrane space and pumps ATP into the matrix
Inner Membrane Space (Mitochondria)
- The space between the outer and inner membrane
- High concentration of protons
Fold in the inner mitochondrial membrane extending into the matrix
What is the function of cristae in the mitochondria?
Cristae helps to increase the surface area
The inner mitochondrial space
What can you find in the mitochondrial matrix?
1. Mitochondrial genetic system
2. Enzymes responsible for oxidative metabolism
What are some of the metabolic reactions that take place in the mitochondrial matrix?
1. Conversion of pyruvate and fatty acids to acetyl-CoA
2. The TCA Cycle
3. Oxidative Phosphorylation
What is the role of the inner membrane (pertaining to permeability)?
The inner membrane is impermeable to most ions and small molecules, which
helps to maintain the proton gradient that drives oxidative phosphorylation
What is more permeable? The inner or outer mitochondria membrane?
The outer membrane
Which membrane of the mitochondria contains porins?
The outer membrane
A type of protein in the outer membrane of the mitochondria that permits the passage of small molecules
A symbiotic relationship in which one cell resides within a larger cell
What is the structure of mitochondrial DNA?
Circular and double stranded
What does mitochondrial DNA code for?
Mitchondrial rRNA and tRNAs, but only some of the mitochondria's mRNA
What rRNAs does human mitochondrial DNA encode?
1. 16S rRNA
2. 12S rRNA
3. 22S rRNA
How is mitochondrial DNA inherited?
From the mother
All the mitochondria of fertilized eggs are contributed by the oocyte rather than by the sperm
Why is that mitochondrial DNA is only inherited from the mother?
Almost all the mitochondria of fertilized eggs are contributed by the oocyte. mtDNA from the sperm is eliminates from the embryo.
What replicates mitochondrial DNA?
DNA Polymerase γ
When daughter cells receive a mixture fo mitochondria, some with normal and some with mutant DNA
When one daughter cell receives mitochondria containing a pure population of either normal or mutant mtDNA
A phenomenon in which phenotypic expression of a mitochondrial disease within an organ system occurs when the severity of the mutation, relative number of mutant mtDNA, and reliance of the organ system on oxidative phosphorylation combine in such a way that ATP production of the tissue falls below the level required by the tissue
Leber's Hereditary Optic Neuropathy (LHON)
- Defect in
(complex I of the electron transport chain)
progressive loss of central vision and blindness
- Though inherited through
, for unknown reasons
affects males more
What codes for most of the proteins required for DNA replication, transcription, and translation in the mitochondria?
What are the stop codons in the mitochondria?
AGA and AGG
Why is it that the mitochondrial genes only have about 20 tRNAs as compared to the univeral code?
Mitochondrial translation has more wobbling
What targets proteins to the mitochondria?
Amino-terminal sequences of 20 to 25 amino acids called
An amino-terminal sequence that targets proteins to the mitochondria.
Mitochondrial Targeting Signal (MTA)
- A sequence usually on the amino terminal of proteins that consist of positively charged amino acids
- Targets proteins to the mitochondria
What is the structure of the presequence?
- Amphipathic alpha helical conformation
- Hydrophobic and hydrophilic resiudes are in the inside
What is the first step in protein import of presequences?
The binding of presequences to receptors on the surface of mitochondria
What is the receptor that presequences bind to?
(Translocase of the Outer Membrane)
The protein translocation complex of the mitochondrial outer membrane
General import pore
The protein translocation complex of the mitochondrial inner membrane
A complex in the inner membrane of mitochondria responsible for mediating the integration of carrier preproteins into the
A complex in the inner membrane of mitochondria that facilitates translocation of matrix-targeted proteins into the
What is required for the transport of proteins through the TIM complex?
Continuing protein translocation requires the
established across the inner mitochondrial membrane during electron transport.
What is the distribution of charge across the inner membrane (mitochondria)?
The side of the intermembrane space is positively charged.
The side of the matrix is negatively charged.
What is the molecular chaperone that helps import proteins into the mitochondria?
Import Motor Complex
A complex that uses ATP hydrolysis to drive mechanical import of the polypeptide through the Tim Complex
A chaperone protein involved in protein folding
How does cystolic Hsp70 help in the import of mitochondrial matrix proteins?
Hsp70 helps fold proteins to go through the Tom complex via ATP hydrolysis.
Part of the TIM translocator, this chaperone protein
binds to imported proteins as they emerge from the TIM channel
, and helps 'pull' the protein into the matrix space using the energy of ATP hydrolysis.
Matrix Processing Peptidase (MPP)
The protease that cleaves presequences from proteins imported to the matrix of mitochondria.
What is the role of Matrix Processing Peptidase (MPP) during protein import in the mitochondria?
Matrix Processing Peptidase (MPP) cleaves the presequence to keep the protein in the mitochondrial matrix.
What is the source of energy for protein import into the mitochondria?
ATP hydrolysis and the electrochemical H+ gradient across the inner mitochondrial membrane
What part of the protein does Hsp70 bind to?
Tim9 and Tim10
- Directs proteins to the inner mitochondrial membrane in order to interact with the TIM22 complex
- Guides β-barrel precursor proteins to the sorting and assembly machinery (SAM) of the outer membrane
Protein transport channel, which facilitates transport from the matrix to the inner membrane
A mitochondrial outer membrane complex which helps single transmembrane domains insert into the outer membrane
A mitochondrial outer membrane complex which helps outer membrane β-barrel proteins fold correctly.
What complex on the inner membrane of mitochondria is similar to Mim1?
Tim complex 22
Where are the phospholipids from the mitochondrial membrane taken from?
The endoplasmic reticulum
Phospholipid Transfer Protein
- A protein that transports phospholipid molecules between cell membranes.
- Transfers between ER and mitochondria
A phospholipid containing four hydrocarbon chains synthesized in the mitochondria
What is the purpose of cardiolipin?
Cardiolipin improves the efficiency of oxidative phosphorylation by
restricting proton flow across the inner membrane
A single-memraned organelle that carries out oxidation reactions leading to the production of hydrogen peroxide
An enzyme that breaks down hydrogen peroxide to water and oxygen
2 H₂O₂ → 2 H₂O + O₂
What biomolecules do peroxisomes help synthesize?
2. Amino acid, lysine
5. Bile acids
- A family of phospholipids in which one the hydrocarbon chains is joined to glycerol by an ether bond rather than an ester bond
- Important membrane components in some tissues, particularly heart and brain
Where does peroxisome assembly begin?
The rough endoplasmic reticulum
What are the two peroxins localized on the rough ER?
An integral transmembrane protein that recruits Pex19 to the ER membrane
What happens after Pex3 interacts with Pex19?
The interaction causes Pex3/Pex19 -containing vesicles to bud off the ER. These nascent peroxisomes fuse with each other or with existing peroxisomes.
What is the peroxin target sequence?
Peroxisome Targeting Signal (PTS1)
- A signal that targets proteins from free ribosome to join peroxisome
- C-terminal tripeptide
Peroxisome Targeting Signal (PTS2)
- A signal that targets proteins from free ribosome to join peroxisome
- Nine amino acids at the amino terminus
What protein recognizes and binds to Peroxisome Targeting Signal (PTS1)?
What protein recognizes and binds to Peroxisome Targeting Signal (PTS2)?
What is the main channel that helps protein import into the peroxisome?
What helps hold together catalase proteins for peroxisome transport?
Peroxisomal disorder resulting in the accumulation of very-long-chain fatty acids because the peroxisome is not properly formed
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