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Intracellular compartments and protein sorting


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Gated Transport
Type of protein transport from the cytosol to the nucleus
Type of transport from the cytosol to the ER, Mitochondria, or peroxisomes
Vesicular Transport
Type of transport from the ER to the Lysosomes, golgi and cell curface
enzymatically break down proteins into constituent amino acids
large complexes of proteolytic enzymes
small protein that covalently attaches to proteins to mark them for destruction and to be recognized by proteasomes
folds of the inner mitochondrial membrane
transport proteins which form large aqueous channels through the lipid bilayer of the mitochondria's outer membrane. Form a Beta barrel
Inner Mitochondrial membrane components:
ETC enzymes (FMN, coenzyme Q, cytochrome a,b,c), succinate dehydrogenase, ATP synthase
Matrix Comparment contents:
TCA enzymes, fatty acid β-oxidation enzymes, DNA, mRNA, tRNA, rRNA, Ca and Mg granules
spherical to ovoid membrane bound organelles w/ 50 oxidative enzymes
uses H2O2 to oxidize other substrates like alcohols, formaldehydes and formic acid (H2O2 + R'H2 --> R' + 2 H2O)
Superoxide dismutase
naturally occuring enzyme in peroxisome that disposes of free radicals
proteinaceous ring that occupies center of Nuclear pore complex and is supported by the scaffold
on the nuclear side of the NPC fibrils converge to form this structure
transport macromolecules (RNA) from the nucleus to cytoplasm
transport cargo (like protein subunits of ribosomes) from the cytosol to the nucleus
Contact sites
Sites of adhesion between the inner and outer mitochondrial membranes through which unfolded proteins are translocated into the matrix from the cytosol
Signal for protein to enter the mitochondria
a positive charge on the N- terminus; 20-80 amino acids in length with an α helix; removed by signal peptidase once in destination
Signal for protein to enter the nucleus
NLS; short signal located anywhere within the polypeptide which is not removed and binds to the nuclear import receptors which direct it to the NPC; unidirectional transport only
Signal for protein to enter peroxisomes:
3 amino acid sequence on the C-terminal that remains on protein
lumen of the endoplasmic reticulum
Signal recognition particles (SRP)
particles in the cytosol that recognize protein ER signal sequence that attach to the P site and halts translation of the protein and migrates to the rough ER with the protein
SRP receptor, docking protein
Contacts the SRP and with rebosomal receptors attaches the polysome to the cytoplasmic surface of the ER; the SRP is released and translation resumed
protein translocation channel
channel in ER membrane through which the growing polypeptide chain inserts into a pore in the ER membrane
Stop transfer sequence
sequence of hydrophobic amino acids that releases the polypeptide chain from the protein translocation channel so it will drift into the bilayer of the ER forming an αhelix of the transmembrane protein (N-terminal in the lumen)
start transfer sequence
er signal sequence in the middle of the polypeptide and ends up forming a transmembrane protein that passes multiple times through the PM
core region
5 sugars (3 are mannose) of the 14 oligosaccaride to glycosylate proteins
process of discharging large cellular products through plasma membrane
acid phosphatase
enzyme in all lysosomes
primary lysosomes
lysosomes that haven't entered a digestive event
tag for lysosomal proteins; tagged in the CGN then sorted itno clathrin coated transport vesicles
signal on protein to be taken up by lysosomes
process whereby lysosomes digest materials taken into cells from its environment by endocytosis
Residual body
any undigested materials in the phagosome or secondary lysosome which are released back into the extracellular fluid by exocytosis
profesional phagocytes
macrophages and neutrophils
process by which worn out organelles are digested
process by which lysosomal enzymes destroy their own cell
mediated transport vesicle from CGN to ER in tetrograde transport
involved in anterograde transport from the ER to CGN
family of transmembrane proteins involved in vesicle docking with unique recognition to ensure that transport vesicles fuse with only the correct membrane
fusion proteins which catalyze membrane fusions and form fusion complex that provide the means to cross this energy barrier
What is the default pathway for proteins made on ER associated ribosomes?
ER to Golgi to secretory vesicles to cell surface
What is the default pathway for proteins made on free ribosomes?
ribosomes to the cytosol
What is the only non-membrane bound organelle
ribosomes to the cytosol
Polysomes bound to ER make what kind of proteins?
make glycosylated proteins
Free polysomes make what kind of proteins?
make non-glycosylated proteins
What are the functions of proteasomes?
rapidly degrade proteins whose lifetime must be short; and recognize and eliminate damaged or misfolded proteins
what is the membrane with the highest protein content in the cell?
inner mitochondrial membrane
What are the two places for β-oxidation?
mitochondria and peroxisomes
Which organelles are the 2 oxygen users in the cell?
mitochondria and peroxisomes
What are the two types of mitochondria
W/ lamellar cristae or tubular cristae
What is the number of cristae directly related to?
the energy requirements of the cell
What are the three characteristics of cells that produce steroid hormones?
1)tubular cristae; 2) lipid droplets (cholesterol) 3) extensive ER networks
How do mitochondria replicate?
Self replication (enlarge, replicate DNA, fission)
What type of cells have no mitochondria?
What are the functions of peroxisomes?
amino acid and fatty acides are oxidized as part of normal metabolism, degrade and form H202, and protect other parts of the cell from the toxic effects of H202
What is the larges membranous surface of the cell?
endoplasmic reticulum
What is the function of the Smooth ER?
site of phospolipid and cholesterol synthesis for cell membranes
What cell types have abundant smooth ER?
gland cells (steroid synthesis), hepatocytes (drug detoxification), striated muscle (Calcium flux)
What is the function of the rough ER?
produce glycosylated proteins destined for lysosomes, export and the plasma membrane
Signal for protein to continue production in or on the ER?
8+ hydrophobic amino acids at the N- terminal that later binds to protein translocation channel to open it and is cleaved while the peptide is threaded through the channel
where are glycosylating enzymes located and in what form do they add sugars
located in the ER lumen only and add preformed 14 sugar oligosaccarides en bloc to an emerging Asn
Where does oligosaccharide processing of proteins occur?
begins in the ER and continues in the Golgi
what are the three functions of the Golgi?
1) alter polysaccharide or oligosaccharide chains 2) plasma membrane recycling 3) sorting of proteins in the TGN
What two types of cells is exocytosis most important?
neurons and secretory cells
3 types of endocytosis
1)receptor mediated endocytosis 2) phagocytosis; 3) pinocytosis
3 types of clathrin coated vesicles
1) vesicles from TGN to late endosomes 2) receptor-mediated endocytosis endosomes 3) regulated secretory vesicles
When are Coatomer coated vesicles used?
non-selective vesicular transport; default pathway from ER--> CGN --> TGN --> PM

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