Part B: Lecture 1 + 2 + 3 + 4 + 5 Flashcards
two ways compartmentalization was achieved
-encased in membrane
-independent of membranes = use molecular environment to create components
why is cellular compartmentalization important?
-increases likelihood of reactions occurring by increasing conc. of rxns in given environments
-prevents side rxns & contamination increasing efficiency
2 factors drive chemical rxns
-conc. of reactions
-the environment
molecules that have _______ characteristics form membranes
hydrophobic & hydrophilic
Stage A of evolution of cell compartmentalization (development of PM)
1) primordial cells may have been vesicles formed by lipid interactions
2) monotopic membrane proteins integrate into those vesicles via insertion sequences
3) vesicle act like capturing device for proteins involved in DNA replication, RNA transcription, protein translation, ribosome assembly
4) Alternations in membrane/ribosome interactions allowed for the integration of bitopic integral membrane proteins
Stage B + C of evolution of cell compartmentalization (Further compartmentalization into closed system)
1) while bitopic proteins are imbedded in membrane, cotranslational translocation develops -> colonization of opposite leaflet by monotopic proteins
2) development of transport system across membrane; cell can communicate with outside world
3) concentration of reaction machinery and prevents interfering rxns
Stage D of evolution of cell compartmentalization (Forming intracellular compartment)
creation of endoplasm compartment and periplasmic space similar to the inside of the precellular vesicle (like Gram - bacteria)- two membrane
Stage E of evolution of cell compartmentalization (Loss of second membrane)
loss of outer membrane could lead to gram + bacteria and precursor for euk cell
Eukaryotic cell compartmentalization is controlled largely _____
by membranes
The membrane of euk cells could be traced to two distinct sources: ______ (2)
1) Invagination of PM of primordial cells + fusion
2) Symbiotic capture of another cell
Invagination of PM of primordial cells for further eukaryotic cell compartmentalization steps
1) nonrandom removal of distinct membrane functions & forming membranes with ectoplasmic compartments
2) formation of nuclear envelope & ER which divides endoplasm into cytoplasm and nuceloplasm, creating double membrane nucleus
3) development of membrane systems like Golgi, secretory vesicles, endocytic vesicles, lysozomes
Symbiotic capture of another cell for further eukaryotic cell compartmentalization steps
1) capture and fusion leads ti double membrane organelles (ex. mitochondria and chloroplasts)
2) Outer mitochondrial and chloroplasts membranes are from the host
3) Inner mitochondrial and inner chloroplasts membranes (+ thylakoid membrane) are from the foreign cel
Protein translocation (def.)
a process by which proteins move between cellular compartments
Types of translocation + def.
cotranslational: coupled to translation.
posttranslational: translocation occurs following synthesis
general structure of mitochondria
-double membrane organelles
-inner membrane
-cristae
-matrix
-outer membrane
outer mitochondrial membrane descr. + function
- membrane contains porin, a protein that forms large channels
- allows the passage of molecules up to 5000 daltons to cross the membrane
- also has lipid synthesis and other enzymes
intermembrane mitochondrial space descr. + function
-beaneath outer membrane
-porin channels allow movement of small molecules across outer membrane so the small molecule composition of space is similar to cytoplasm
inner mitochondrial membrane descr. + function
-inner membrane forms extensive cristae (flattened adjacent membrane) which increase SA of inner membrane
-site of oxidative reactions involved in respiratory chain; location of ATP synthase
mitochondrial matrix descr. + function
-contains enzymes involved in oxidation of pyruvate and the citric acid cycle
Oxidative metabolism in cells is performed by ____, which serves as the major ______ in eukaryote cells. This is accomplished ultimately by the oxidation of _____ in the citric acid cycle leading to the production of _____. The reduction of NAD to NADH provides a source of high energy electrons used in a ______. The proton gradient essentially represents a form of stored energy that can be used by ________. ATP is then transported to the cytoplasm.
-mitochondria
-energy-converting organelle
-Acetyl – CoA
-NADH & FADH2
-chemiosmotic coupling reaction
-ATP synthase to convert ADP → ATP
The mitochondrial matrix also contains the mitochondrial _____
DNA genome, mitochondria ribosome, tRNA, etc
Mitochondrial proteins are targeted to several specific locations (4)
1) Outer membrane
2) Intermembrane space
3) Inner membrane
4) Matrix
Early studies: sorting signal for targeting mitochondrial matrix proteins was in ____. The mitochondrial signal sequence was made of _____
-a stretch of N-terminal a.a residues
-positively charged a.a residues that aligned in one face of amphipathic helix
Mitochondrial proteins are synthesized where?
on free ribosomes
Requirements for import into mitochondria
- Membrane potential across the inner mitochondrial membrane.
- ATP hydrolysis
- molecular chaperones -> proteins of the hsp70 family that interact with mitochondrial proteins; maintain the mitochondrial proteins in an unfolded state and thus an import-component state.
-receptors on the surface of the mitochondria that interact with precursors + chaperones
Mitochondrial proteins imported into mitochondria first interact with a _____ at the surface of the outer membrane (_____). At some point before or during translocation the outer membrane complex engages an inner membrane complex (_____ ) to form contact sites at points of translocation.
-receptor complex
-the TOM complex
-the “TIM complex”
Mitochondria: translocation continues through this inner pore (_______) and the _____ go through a continuous cycle of _____ to segment of the polypeptide emerging from the channel
-the TIM complex
-mt-hsp70
-binding, releasing, and rebinding
As the polypeptide enters the matrix _____ is released in an ____-dependent manner and is replaced by another mitochondrial chaperone, _____, which assists in the _____
-mt-hsp70
-ATP
-mt-hsp60
-folding of a protein into its mature form
Proteins that are destined for the intermembrane space are translocated through the ______. The TOM complex and other complexes mediate the _____
-TOM complex directly into the intermembrane space
-direct integration of membrane proteins into the outer membrane
Kunkele paper showed two things: _____
-isolated TOM complex & characterized the pore
-reincorporated complex into membranes so they could view activity of channel
TOM complex major parts (4)
-TOM 70, TOM 40, TOM 20, TOM 22
TIM complex major parts (4)
-TIM 23/17, Pam17, mtHsp70, TIM 50
Ways to isolate TOM complex
-lyse cells
-separate mitochondrial membranes
-density centrifugation
how density centrifugation works?
-organelles have different sizes/density
-largest organelles, nucleus then mitochondria pellet first
-ER breaks into smaller vesicles -> microsomes
