Term
| What is the endosymbiont theory? |
|
Definition
| Believes organelles of eukaryotic cell evolved from prokaryotic cells which entered a host cell |
|
|
Term
| What is the function of mitochondria in eukaryotic cells? |
|
Definition
| -energy production from carbohydrate & lipid catabolism |
|
|
Term
| What is the function of chloroplasts in eukaryotic cells? |
|
Definition
| -energy production & carbohydrate synthesis via photosynthesis |
|
|
Term
True or False
Mitochondria & chloroplasts contain their own DNA unique from other organelles |
|
Definition
|
|
Term
| Explain the statement "mitochondria and chloroplasts are semi-autonomous" |
|
Definition
| Organelle replication is controlled by both the cell & the organelle itself |
|
|
Term
True or False
Mitochondria and chloroplasts can be produced "from scratch" |
|
Definition
False
They can only arise from pre-existing organelles |
|
|
Term
| What are the characteristics of the outer mitochondrial membrane? |
|
Definition
-permeable to ions & small molecules
-contains porins (integral proteins with an internal channel) |
|
|
Term
| What are the characteristics of the inner mitochondrial membrane? |
|
Definition
-impermeable
-forms cristae which extend into interior of the organelle |
|
|
Term
| Where is the proton concentration greater, in the intermembrane space or in the matrix? |
|
Definition
| in the intermembrane space |
|
|
Term
| What is found within the mitochondrial matrix? |
|
Definition
| mitochondrial genome & ribosomes |
|
|
Term
| Which proteins are encoded in the mitochondrial matrix? |
|
Definition
| proteins relating to the mitochondrial genome |
|
|
Term
True or False
Mitochondria operate independently from each other |
|
Definition
False
They form a highly branched mitochondrial network |
|
|
Term
| What makes the mitochondrial network a highly dynamic network? |
|
Definition
| the tubules can undergo fission & fusion depending on the developmental status & energy needs of the cell |
|
|
Term
| What must occur first, fusion of the outer or inner membranes? Why is this important? |
|
Definition
| outer membranes must fuse first, in order to maintain subcompartmentalization |
|
|
Term
| What are the general steps of mitochondrial fusion? |
|
Definition
1. outer membrane tethering
2. outer membrane fusion
3. inner membrane fusion |
|
|
Term
| Describe the process of tethering the outer mitochondrial membrane? |
|
Definition
| -GTPase mitofusins form an organelle tethering complex |
|
|
Term
|
Definition
| GTPase mitofusins which link together in the tethering of the outer mitochondrial mmb |
|
|
Term
| Describe the process of fusing the outer mitochondrial membrane? |
|
Definition
-lipid microdomains form on the outer membrane, where Mnf1/2 tethering has occured
-cardiolipin is converted to phosphatidic acid
-inward curvature is intitiated |
|
|
Term
|
Definition
Phospholipase D
-an enzyme which converts cardiolipin to phosphatidic acid |
|
|
Term
| What is the function of phosphatidic acid? |
|
Definition
| -causes the outer mito mmb to curve inwards & promotes Mfn1/2 mediated membrane fusion |
|
|
Term
| What mediates the fusion of the inner mitochondrial membrane? |
|
Definition
| Optic Atrophy 1 (OPA1) GTP-ase proteins on adjacent inner membranes interact to promote fusion |
|
|
Term
| What prevents cristae of an inner membrane from self-fusing? |
|
Definition
|
|
Term
| Where are the majority of mitochondrial proteins encoded? Synthesized? |
|
Definition
| encoded in the nucleus, synthesized on free ribosomes |
|
|
Term
| What is a mitochondrial RNA cloud? What is its purpose? |
|
Definition
region of mitochondrial mRNA concentrated in the cytosol, near the mitochondrion itself
facilitates fast & efficient post-translational protein targeting to mitochondria |
|
|
Term
| What mediates formation of a mitochondrial RNA cloud? |
|
Definition
| cytoskeleton & RNA binding proteins on the outer surface of mitochondria |
|
|
Term
| What are mitochondrial zipcodes? |
|
Definition
| specific AA sequences which mediate protein targeting from cytosol to surface of mitochondrian & specific mitochondrial subcompartments |
|
|
Term
| What is a mitochondrial pre-sequence, where is it found and what is its purpose? |
|
Definition
15-50 alpha helical AA targeting signal found on the N terminus of a protein
-targeting protein to cytosolic surface of mitochondrion
-translocation of protein across inner & outer mito mmbs |
|
|
Term
| What are the general steps of targeting & import of proteins into the mitochondrial matrix? |
|
Definition
1. Recognition of nascent protein by cytosolic chaperones
2. Recognition of N-terminal sequence by TOM complex on mitochondrial surface
3. Protein is passed from TOM complex to TIM23, and translocated into mito matrix
4. N-terminal presequence binds to mtHsp70, is pulled further into matrix & presequence is cleaved |
|
|
Term
| What is the function of cytosolic chaperones in matrix protein import? |
|
Definition
-recognizes nascent proteins in cytosol
-keeps protein in a partially-unfolded state to enable import |
|
|
Term
| What is the TOM complex? What are its components? |
|
Definition
Translocase of the mitochondrial Outer Membrane
receptor: binds to +ve presequence
channel: mediates translocation across outer mmb
accessory proteins: scaffolding to mediate transfer from receptor to channel |
|
|
Term
| What is the TIM23 complex? What is its purpose? |
|
Definition
Translocase of the Mitochondrial Inner Membrane 23
-forms a channel for protein translocation across inner mito mmb |
|
|
Term
| What drives translocation of a protein through TOM and TIM23? |
|
Definition
proton concentration gradient
-positively charged protein is more attracted to the matrix, where there are fewer H+ |
|
|
Term
| What is mtHsp70? What is its function? |
|
Definition
MiTochondrial Heat-Shock Protein of 70kd
an ATP-dependent molecular motor chaperone which pulls the protein further into the matrix, preventing it from sliding back into the cytosol |
|
|
Term
| How is the N-terminal presequence cleaved from the protein upon entering the matrix? What happens next? |
|
Definition
| Mitochondrial Processing Peptidase (MPP) cleaves the N-terminal presequence, chaperone proteins then mediate folding of the mature protein |
|
|
Term
| How do mitochondria produce energy? |
|
Definition
lipid/carbohydrate catabolism
(Kreb's Cycle & ETC) |
|
|
Term
| Where is the mitochondrial genome found? |
|
Definition
| in the mitochondrial matrix |
|
|
Term
According to the endosymbiont theory, what is the origin of the following organelles?
Mitchondria
Nuclear Envelope & ER
Chloroplast |
|
Definition
Mitochondria: originated from an engulfed aerobic prokaryote
NE & ER: invagination of the plasma membrane
Chloroplast: engulfed photosynthetic bacterium |
|
|
Term
True or False
The inner mito mmb is permeable while the outer membrane is not |
|
Definition
False
The inner membrane is the impermeable one |
|
|
Term
| What is the function of phospholipase D? |
|
Definition
| converts cardiolipin into phosphatidic acid to promote membrane curvature & fusion between 2 outer membranes |
|
|
Term
| What proteins promote fusion of inner mitochondrial membranes? |
|
Definition
|
|
