Intracellular compartments and protein sorting
Terms
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- Gated Transport
- Type of protein transport from the cytosol to the nucleus
- TransmembraneTransport
- 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
- Proteolysis
- enzymatically break down proteins into constituent amino acids
- Proteasomes
- large complexes of proteolytic enzymes
- Ubiquitin
- small protein that covalently attaches to proteins to mark them for destruction and to be recognized by proteasomes
- Cristae
- folds of the inner mitochondrial membrane
- Porins
- 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
- Peroxisomes
- spherical to ovoid membrane bound organelles w/ 50 oxidative enzymes
- catalase
- 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
- transporter
- proteinaceous ring that occupies center of Nuclear pore complex and is supported by the scaffold
- Cage
- on the nuclear side of the NPC fibrils converge to form this structure
- Exportins
- transport macromolecules (RNA) from the nucleus to cytoplasm
- Importins
- 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
- cistern
- 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
- Exocytosis
- 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
- mannose-6-phosphate
- tag for lysosomal proteins; tagged in the CGN then sorted itno clathrin coated transport vesicles
- KFERQ
- signal on protein to be taken up by lysosomes
- heterophagy
- 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
- Autophagy
- process by which worn out organelles are digested
- autolysis
- process by which lysosomal enzymes destroy their own cell
- COP-I
- mediated transport vesicle from CGN to ER in tetrograde transport
- COP-II
- involved in anterograde transport from the ER to CGN
- SNAREs
- family of transmembrane proteins involved in vesicle docking with unique recognition to ensure that transport vesicles fuse with only the correct membrane
- NSF and SNAPs
- 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?
- erythrocytes
- 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