Chapter 11 Flashcards

endoplasmic reticulum (ER)

An extensive network of membrane-enclosed tubules and sacs involved in protein sorting and processing as well as in lipid synthesis.

rough ER

The region of the endoplasmic reticulum (ER) covered with ribosomes and involved in protein metabolism.

smooth ER

The region of the endoplasmic reticulum (ER) that is the major site of lipid synthesis in eukaryotic cells.

secretory vesicle

A membrane-enclosed sac that transports proteins from the Golgi apparatus to the cell surface.

secretory pathway

The movement of secreted proteins from the endoplasmic reticulum to the Golgi apparatus and then, within secretory vesicles to the cell surface.

signal sequence

A hydrophobic sequence at the amino terminus of a polypeptide chain that targets it for secretion in bacteria or incorporation into the endoplasmic reticulum in eukaryotic cells.

SRP RNA

The small cytoplasmic RNA component of SRP.

SRP receptor

A protein on the membrane of the endoplasmic reticulum that binds the signal recognition particle (SRP).

translocon

The membrane channel through which polypeptide chains are transported into the ER.

signal pepitdase

An enzyme that removes the signal sequence of a polypeptide chain by proteolysis.

protein disulfide isomerase (PDI)

An enzyme that catalyzes the formation and breakage of disulfide (S-S) linkages.

glycosylphosphatidylinositol (GPI) anchors

A glycolipid containing phosphatidylinositol that anchors proteins to the external face of the plasma membrane.

ER-associated degradation (ERAD)

A process in which misfolded proteins in the ER are identified and returned to the cytosol for degradation by the ubiquitin-proteasome system.

unfolded protein response

A cellular stress response in which an excess of unfolded proteins in the ER leads to general inhibition of protein synthesis, increased expression of chaperones, and increased proteasome activity.

flippase

A protein that catalyzes the translocation of lipids across the membrane of the ER.

Golgi apparatus

A cytoplasmic organelle involved in the processing and sorting of proteins and lipids. In plant cells, it is also the site of the synthesis of cell wall polysaccharides.

Golgi complex

A cytoplasmic organelle involved in the processing and sorting of proteins and lipids. In plant cells, it is also the site of the synthesis of cell wall polysaccharides.

cis

The Golgi cisterna oriented closest to the nucleus, which receives transport vesicles from the ER-Golgi intermediate compartment.

trans compartment

The Golgi cisterna oriented furthest from the nucleus.

trans-Golgi network

The Golgi compartment within which proteins are sorted and packaged to exit the Golgi apparatus.

mannose-6-phosphate

A modified mannose residue that targets proteins to lysosomes.

apical domain

The exposed free surface of a polarized epithelial cell.

basolateral domain

The surface region of a polarized epithelial cell that is in contact with adjacent cells or the extracellular matrix.

vesicle coat protein

Multimeric proteins (COPI, COPII, clathrin) with a triskelion structure that assemble on the cytoplasmic surface of membranes, which drives vesicle budding.

clathrin

A protein that coats the cytoplasmic surface of cell membranes and assembles into basket-like lattices that drive vesicle budding.

COPI

With COPI, the two proteins other than clathrin that coat transport vesicles (COP indicates coat protein)

COPII

With COPII, the two proteins other than clathrin that coat transport vesicles (COP indicates coat protein)

COPII-coated vesicle

A transport vesicle coated with COPII that mediates transport from the ER to the Golgi apparatus.

COPI-coated vesicle

A transport vesicle coated with COPI that mediates retrieval from the Golgi apparatus to the ER.

clathrin-coated vesicle

A transport vesicle coated with clathrin.

tethering factor

A protein that mediates the initial interactions between transport vesicles and their target membranes.

Rab

A family of small GTP-binding proteins that play key roles in vesicular transport.

proteins

Polypeptides with a unique amino acid sequence.

SNARE

A transmembrane protein that mediates fusion of vesicle and target membranes.

lysosome

A cytoplasmic organelle containing enzymes that break down biological polymers.

lysosomal storage disease

A family of diseases characterized by the accumulation of un-degraded material in the lysosomes of affected individuals.

endocytosis

The uptake of extracellular material in vesicular formed from the plasma membrane.

endosome

A vesicular compartment involved in the sorting and transport to lysosomes of material taken up by endocytosis.

autophagy

The degradation of cytoplasmic proteins and organelles by their enclosure in cytoplasmic vesicles that fuse with lysosomes.

autophagosome

A vesicle containing internal organelles enclosed by fragments of cytoplasmic membranes that fuses with lysosomes.

autolysosome

A structure formed by the fusion of a lysosome and an autophagosome containing damaged and/or old intracellular substances during the process of autophagy.

autophagy-related (Atg) protein

A family composed approximately 20 proteins that function together to carry out autophagy.

phagophore

An expanding double membrane structure docked at the ER in the early stage of autophagy.