Lecture 11 - Endomembranes & ER Flashcards
def: sites for protein and lipid synthesis, processing and sorting
- rough and smooth ER
- golgi complex
def: carry and sort material bought into the cell
endosomes
def: digest ingested material and unneeded cellular components
lysosomes
def: move molecules between the compartments and plasma membrane
transition, transport and secretory vesicles
def: house hydrogen peroxide generating reactions
peroxisomes
def: store ions, sugars, amino acids, and toxic compounds
vacuoles
from the protein synthesis perspective, what is the start of the endomembrane system?
the rough endoplasmic reticulum
the rough ER consists of tubular membranes and flattened sacs called _______
cisternae
about ___ of the proteins are synthesized in the RER
1/3
where are these proteins produced in the cell:
- secreted proteins
- transmembrane proteins
- soluble proteins that reside in the ER, Golgi complex, lysosomes, endosomes vesicles, and vacuoles
rough ER
where are these proteins synthesized:
- ones destined to remain in the cytosol
- peripheral proteins of the cystolic surface membranes
- proteins that are transported to the nucleus
- proteins that are incorporated into peroxisome, chloroplasts and mitochondria
on “free” cytosolic ribsomes
where do all proteins BEGIN synthesis?
on ribosomes in the cytosol
how do proteins know where they need to go?
information is coded in the primary sequence: ER signal sequence or sorting signal
how can the compartments of the eukaryotic cell be divided?
- the endomembrane system
- the cytosol
- the mitochondria, chloroplasts, peroxisomes, and the interior of the nucleus
what are the 2 pathways for routing the protein products?
- free ribosomes
- ER docked ribosomes
most membrane proteins take which pathway of protein synthesis?
ER-docked ribosomes
what are the 2 pathways of protein sorting?
- co-translational import
- post-translational import
def: protein sorting - proteins carrying an ER signal sequences direct the ribosomes-polypeptide complex to the rough ER, translation is completed on the rough ER and then process and sorted in the ER and Golgi
co-translation import
def: protein sorting - proteins lacking an ER signal sequence complete their synthesis on ribosomes that are free in the cytoplasm, proteins are released into the cytoplasm and the ones with an organelle-specify sorting signal are imposed into the organelle
post-translational import
do cytoplasmic proteins have sorting signals
no they remain in the cytoplasm
co-translational import is considered a _________ pathway while post-translational import is a _____________ pathway
secretory, non-secretory
def: multiple ribosomes synthesizing the same mRNA
polysome
sorting signals direct proteins to _______ __________-
their compartments
an ER signal sequence directed the polypeptide/ribosme to the __ __________
ER membrane