lec 15 Flashcards
(18 cards)
golgi apparatus
- when vesicles leave the ER
- transported to the golgi
> undergo specific covalent mod - made of a series of cisternae
- cis face = closest to the ER
- vesicles from the ER fuse at the cis golgi network of cisternae - cargo leaves the Golgi in vesicles from the trans face
oligosaccharide processing in the golgi
- occur in an organized seq as proteins go from cis to trans
- each cisterna has characteristic processing enzymes
- stack forms multistage processing unit - when vesicles leave the golgi
- have a new transport
> targeting and fusion info
covalent alteratins in the golgi
sugar assembly/glycosylation
- cell-specific
transport from trans golgi to the plasma membrane
membrane targeting, transport, and fusion
1. constitutive delivery and secretion
- automatic transport from trans golgi to plasma membrane
- occurs continuously
2. regulated secretion
- specialized vesicles dock at the cytoplasmic side of the plasma membrane
- req 2ndary signal to cause the fusion
- needs external signals to trigger the vesicle func/secretion
> used for the release of neurotransmitters and hormones
lysosome targeting, transport and fusion
lysosomal enzymes = deadly
- optimal pH = 5
- acid hydrolases
- made in ER
- placed in lumen
- inactive at ER pH
- co-translationally transported into the rough ER
> goes to the golgi
= tagged w/ M6P
> transmembrane protein receptor M6P in TGN bind to M6P tagged proteins on luminal side
=bind coat proteins on cytosolic side
signal patch on lysosomal hydrolases instructs the addition of M6P
- in golgi
signal patches
- separated stretches of amino acids brought together by tertiary folding
- occurs after folding is complete
endocytosis
endocytosed molecules = released in endosomes or lysosomes
mitochondrial targeting and transport
many nuclear mitochondrial proteins
- translated on free ribosomes in the cytosol
mitochondrial signal seq = recognized by proteins that aid in transport to mitochondria
- no vesicles involved
mitochondrial targeting
specific seq within the mitochondrial proteins target to mitochondrial translocator
1. TOM (Translocator of Outer Membrane)
2. TIM (Translocator of Inner Membrane)
what are the cell’s req to be in the cytoskeleton?
- correctly shaped
- robust
- properly structured internally
- rearrange internal components as they grow, divide and adaot to changing circumstances
- change shape and move
cytoskeleton func
- maintaining general shapes and internal structures of cells
- providing mechanical strength
- enabling cell movement
- guiding intracellular traffic of organelles and molecules
- facilitating cell division
3 fibrous components of cytoskeletal sys
- actin filament (microfilament)
- cell shape, movement, junction, division, and intracellular transport - microtubules
- intracellular transport, cell division, cilia and flagella - intermediate filaments
- mechanical strength
structural polarity
structural differences at opposite ends of the filament
- in microtubules and actin filaments cause 1 pole to polymerize (addition of subunits) and depolymerize faster than the other pole
rates of de/polymerization depend on
- affinity of different poles for free subunits
- concentration of free subunits present
- action of regulatory microfilament/microtubule-associated proteins
changes in concentration in the free subunits
(+) end =»_space; affinity for free subunits
- grows quickly on (+) end
conc of free subunits = «
- net shrinkage at both ends
- shrinkage = faster at (+) end
more intermediate conc of free subunits
- net growth at (+) end with net shrinkage at (-)
- OR net growth at both ends
> growth rate = faster at (+) end
actin filaments
2-stranded helical polymers of the protein actin
- individual actin monomer = g-actin
- actin filaments = f-actin
actin filaments grow by reversible addition of monomers to both ends of the filament
monomers bind to ATP
- hydrolyzed to ADP following filament assembly
ATP is not required for polymerization
- actin monomers to which ATP is bound polymerize much more readily than those to which ADP is bound
actin polymerization
- reversible process
- monomers both associate with and disassociate from the ends of the actin filaments - involves ATP-hydrolysis
- g-actin = added to growing filament in ATP-bound state
> hydrolyzed to ADP once added to the filament
