The Endomembrane System Flashcards
vesicles
small-membrane enclosed sacs that transport substances within a cell or from ther interior to the exterior of the cell; form by budding off an organelle, taking piece of membrane and internal contents of the organelle to refuse with another organelle or plasma membrane
endomembrane system
a cellular system that includes the nuclear envelope, the ER, the golgi apparatus, lysomes, the plasma membrane, and the vesicles that move between them
exocytosis
vesicles fusing with the plasma membrane, releasing contents into the outside of the cell
endocytosis
capturing substance from outside the cell by endgulfing it with cell membrane to bring it into the cell
nuclear envelope
boundary of the nucleus
nuclear pore
large protein complexes that allow the movement of molecules into and out of the nucleus
ribosomes
the site of protein synthesis; amino acids assembled into polypeptide chains through information in teh mRNA
endoplasmic reticulum ER
organelle bounded by a single membrane; continuout with the outer membrane of the nuclear envelope; prodeces and transports proteins and lipids used both inside and outside of the cell
lumen
interior of the endoplasmic reticulum ER
rough endoplasmic reticulum RER
the part of the ER studded with ribosomes; synthesizes transmembrane proteins, proteins that end up in the interior of organelles, and proteins destined for secretion
smooth endoplasmic reticulum SER
the part of the ER without ribosomes; site of fatty acid and phospholipid biosynthesis
golgi apparatus
ER → golgi apparatus → rest of the cell; modifies proteins and lipids produed by the ER; sorting station as proteins and lipids move to their final destination; site of synthesis of cell carbohydrates
cisternae
series of flattened membrane sacs that make up the golgi appartus
glycocylation
chemical modification in the golgi appartus in which sugars are covalently linked to lipids or specific amino acids of proteins to form glycoproteins
glycoproteins
important components of eukaryotic cell surface; sugars attached to proteins protect it from enzyme digestion by blocking acess to peptide chain → forms flexible and protective coat over the plasma membrane
lysome
specialized vesicles derrived from the golgi apparatus; degrades damaged and unneeded macromoleucles; pH ~ 5; selectively permeable
protein sorting
process by which proteins end up where they need to be to perform their function
signal sequence
proteins produec on free ribosomes have amino acid sequences → allowing them to be recognized and sorted; no signal sequence → remain in the cytosol; proteins produced on the RER → end up on the lumen of the endomembrane system, secreted out of the cell, or as transmembrane proteins
nuclear localization signals
nuclear signal sequences enebale proteins to move through pores in the nuclear envelope
signal-recognition particle SRP
RNA-protein complex recognizes a sequence as a free ribosome translates a protein in the cytosol; binds to signal sequence and the free ribosome → pauses translation → SRP binds with the receptor on the RER → ribosome becomes associated with RER → SRP receptor brings ribosome to channel in membrane of RER → SRP dissociates and translation continues allowing for growth of the polypeptride chain to be threaded through the channell
signal-anchor sequence
proteins destined for cell membranes contain SAS