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Terms in this set (38)
Refers to the targeting and transport of proteins to specific cellular organelles.
-requires signal mechanism
-requires transport method
Refers to the making of proteins and their modifications through the ER and Golgi.
-post-translation modifications occur
a membrane system that forms a channel (lumen) within the cytosol of the cell.
-synthesis of steroid hormones
-detoxification of chemical compounds
-glucose conversion in the liver
Contains ribosomes on cytosolic face.
-synthesis of trans-membrane proteins
-post translational modification of proteins
-quality control functions
Enzyme which cleaves the signal peptide from the growing nascent peptide chain.
Protein Disulfide Isomerase
Enzyme which catalyzes the formation and shuffling of disulfide bonds.
Specialized structures which degrade misfolded proteins.
Enzymes which add an oligosaccharide chain to a protein.
Ribosomes which attach to the Rough ER make:
-Integral Membrane (membrane spanning) Proteins
-Endomembrane system proteins
-Proteins destined for lysosomes
Free Ribosomes make:
-Proteins that stay in the cytosol
-Proteins which are imported into the nucleus
-Proteins destined for the peroxisome
-Proteins destined for the mitochondria
-Proteins destined for the chloroplast
The N-teminal of the nascent polypeptide-
Encodes a signal peptide which directs the Ribosomes to the RER.
-Signal sequence on the N-teminal (makes sense peptides are formed N-first)
-Signal recognition particle (SRP- protein) binds to the recognition sequence
-The ribosome is directed to the ER membrane
-Translocon-term for the protein channel where the ribosome attaches and inserts nascent strand
-Cotranslational transport-peptide translation during transport through the ER. Transport and translate at the same time.
Proteins needed by RER pathway
-Enzymes used for biogenesis, i.e. glycosylases
-Vesicle coat proteins
Released by Exocytosis i.e. insulin ( go through RER/Golgi)
Membrane Spanning (Integral) Proteins
Receptors, ion channels, aquaporins
Targeting a Ribosome to the RER
All proteins targeted to the RER will have an N-terminal Signal Peptide sequence which is recognized by the Signal Recognition particle.
-BIP= Binding Protein "Heat Shock"
Integral Protein Synthesis
Overview of integral protein synthesis. SRP and SRP Receptor, are involved as depicted earlier. In addition there is a Stop-Transfer Anchor sequence which signals the channel to stop importing into the ER and to translocate the peptide through the channel proteins into the membrane.
A fibrous lattice protein which forms on the cytosolic face of the membrane pulls the membrane into pits to form vesicles.
-transport from Golgi to cytoplasmic membrane and back.
Protein coating on vesicles which travel form ER to cis-Golgi - antero-dircted
Protein coating on vesicles which travel form Cis-Golgi to trans-Gogi (antero directed) and from the Golgi back to the ER and between Golgi cisternae (retro directions).
-Contents stored in vesicles
-Vesicles triggered to release based on signal
-Cell has polar structure
How are vesicles directed to the correct membrane for fusion?
-Phospholipid content of membrane
-Specific proteins on the vesicles and the membranes of the organelle (similar to receptor-ligand matching)
-Movement of vesicle to target membrane on microtubule and motor protein
-Tethering of vesicle to target compartment membrane through proteins
-Docking of vesicle to target compartment membrane with SNARES
-Fusion of vesicle to target compartment membrane through SNARES
Receptor Mediated Exocytosis
Drugs that bind to the sulphonylurea receptor can stimulate insulin secretion. Examples include:
Are specialized vesicles which fuse with endosomes and degrade their contents.
-Proteins/Enzymes directed to the lysosomes have a phosphorylated mannose which acts as a signal
Are vesicles formed from endocytosis which contain recycled proteins, and foreign materials like bacteria which will be degraded.
-A endocytosed vesicle with a foreign substance (bacteria) will fuse with a lysosome and be degraded.
Lysosomal Storage Disease
Malfunction of the lysosome mechanism.
-Enzyme wont break down material
Problem with export after breakdown
Polypeptides produced in the Cytosol
Needed by Cytosol (no targeting sequence)
Polypeptides produced in the Cytosol but are directed to an organelle:
-Needed by Mitochondria
-Needed by Nucleus
-Needed by Peroxisome
-Needed by the Chloroplast
The Mitochondria is important in cellular homeostasis
-Provided oxidative phosphorylation to produce ATP to meet cellular energy needs
-Contains a double lipid bilayer membrane where Oxidative Phophorylation occurs
-Many protein enzyme complexes reside in the membrane and within the mitochondria
Nuclear Pore Complex
Proteins which form a basket-like complex which extends into cytoplasm and nucleoplasm
Nuclear Localization Signals (NLS)
Amino acid sequences which direct a protein to import into the nucleus
Nuclear Export Sequences
Amino acid sequences which direct a protein out of the nucleus
Proteins involved in this process are called:
-GTP exchange and GTP hydrolysis
Proteins which direct proteins into the nucleus
Proteins that direct RNA out as complexes with protein
GTP exchange and GTP hydrolysis
Proteins regulate guanine binding state of a protein
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