Cell Bio Ch 12 & 13 Flashcards
Cytoplasm
Cytosol and cytoplasmic organelles
Nucleus
Contains genome; DNA and RNA synthesis
Cytosol
Site of protein synthesis and degradation; constitutes more than 50% of the total volume of the cell
Endoplasmic reticulum
Synthesis of most lipids; synthesis of proteins for distribution to many organelles and the plasma membrane
Also works as a store for Ca++ used in many signaling cascades
Golgi apparatus
Receives lipids and proteins from the ER, then dispatches to different locations
Mitochondria/chloroplast
Generates most of ATP to drive reactions
Endosomes
Endocytosed materials first come to endosomes
Lysosomes
Contain enzymes that degrade defunct Intracellular organelles
Peroxisomes
Oxidation of toxic materials
Three major forms of intracellular transport of proteins
Gated- between cytosol and nucleus
Transmembrane- translocators and transporters
Vesicular transport- membrane enclosed vesicles transport proteins from one compartment to another
___________ direct proteins to the correct locations
Signal sequences; “routing tags” consisting of certain amino acid sequences
____________ occurs continuously between the nucleus and the cytosol.
Bidirectional traffic
Protein structure that provides structural support to the nuclear envelope
Nuclear lamina
Nuclear pore complex (NPC)
Made up of 30 proteins called nuclear porins
Made of 4 subunits with tendrils on both sides
Tendrils inside nucleus form a basket shape
Pass 500 macromolecules per sec
______________ direct proteins from the cytosol to the nucleus.
Nuclear localization signals (NLS)
Bind to proteins and bring them into the nucleus
The import and export across NPC requires energy which is obtained by hydrolyzing ________ to ___________.
GTP to GDP
________ is found in both the nucleus and the cytosol and is required for both import and export of proteins in the nucleus.
Ran
Endoplasmic reticulum is organized in:
A net-like labyrinth of branching tubules and flattened sacs continuous from the nuclear membrane
Internal space form by the continuous sheet of the nuclear membrane and the ER membrane
ER lumen
________ ER produces proteins, and _______ ER produces lipids
Rough, smooth
All proteins delivered to the exterior of the cell must pass through the ______
ER
_________ makes up most of the cells lipids.
ER
Types of protein translocation to ER
Co-translation translocation- proteins imported into the ER before complete synthesis.
Post-translation translocation- ribosomes complete protein synthesis and release protein before it is taken in be ER
Many ribosomes attached to a single mRNA molecule
polyribosome
Membrane bound and free ribosomes differ only in:
the proteins they are making
Two components that guide the ER signal sequence
- SRP (signal recognition particle) travels between ER membrane and cytosol, binds to signal sequences
- SRP receptor
The ______ on the protein directs the ribosome towards a translocator on the ER
signal sequence
The ______ forms a pore in the membrane that allows the polypeptide to be _______.
translocator, translocated
________ clips off the signal sequence and releases the mature protei into the ER.
Signal peptidase
