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Flashcards in Kapitel 13 Deck (64)
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Compartment formed from a bulbous - vacuolar portion of early endosomes by a process called endosome maturation; late endosomes fuse with one another and with lysosomes to form endolysosomes that degrade their contents.

late endosome


Large complex composed of a single protein molecule and many esterified cholesterol molecules - together with other lipids. The form in which cholesterol is transported in the blood and taken up into cells. (Figure 13–51)

low-density lipoprotein (LDL)


Genetic diseases resulting from defects in or a lack of one or more functional hydrolases in lysosomes of some cells - leading to accumulation of undigested substrates in lysosomes and consequent cell pathology.

lysosomal storage diseases


Membrane-enclosed organelle in eukaryotic cells containing digestive enzymes - which are typically most active at the acid pH found in the lumen of lysosomes. (Figure 13–37)



Transmembrane receptor proteins present in the trans Golgi network that recognize the mannose 6-phosphate (M6P) groups added exclusively to lysosomal enzymes - marking the enzymes for packaging and delivery to early endosomes.

M6P receptor proteins


Phagocytic cell derived from blood monocytes - resident in most tissues but able to roam. It has both scavenger and antigen-presenting functions in immune responses.



Clathrin-independent - dedicated degradative endocytic pathway induced in most cell types by cell-surface receptor activation by specific cargoes.



Intermediates in the endosome maturation process; early endosomes that are on their way to becoming late endosomes.

multivesicular bodies


White blood cell that is specialized for the uptake of particulate material by phagocytosis. Enters tissues that become infected or inflamed. (Figure 24–5)



Hexameric ATPase that disassembles a complex of a v-SNARE and a t-SNARE. (Figure 13–20)



Addition of one or more sugars to a hydroxyl group on a protein.

O-linked glycosylation


Process by which unwanted cells - debris - and other bulky particulate material is endocytosed (“eaten”) by a cell. Prominent in carnivorous cells - such as Amoeba proteus - and in vertebrate macrophages and neutrophils. From Greek phagein - to eat.



Large intracellular membrane-enclosed vesicle that is formed as a result of phagocytosis. Contains ingested extracellular material. (Figure 13–61)



A lipid containing a phosphorylated inositol derivative. Minor component of the plasma membrane - but important in demarking different membranes and for intracellular signal transduction in eukaryotic cells. (Figure 13–10)

phosphoinositides (PIPs; phosphatidylinositol phosphates)


Literally - “cell drinking.” Type of endocytosis in which soluble materials are continually taken up from the environment in small vesicles and moved into endosomes along with the membrane-bound molecules. Compare phagocytosis. (Figure 13–48)



An ordered recruitment of sequentially acting Rab proteins into Rab domains on membranes - which changes the identity of an organelle and reassigns membrane dynamics.

Rab cascade


Molecules that bind activated - membrane-bound Rab proteins and act as downstream mediators of vesicle transport - membrane tethering - and fusion.

Rab effectors


Monomeric GTPase in the Ras superfamily present in plasma and organelle membranes in its GTP-bound state - and as a soluble cytosolic protein in its GDP-bound state. Involved in conferring specificity on vesicle docking. (Table 15–5 - p. 854)

Rab proteins


Internalization of receptor–ligand complexes from the plasma membrane by endocytosis. (Figure 13–52)

receptor-mediated endocytosis


Organelle that provides an intermediate stage on the passage of recycled receptors back to the cell membrane. Regulates plasma membrane insertion of some proteins. (Figure 13–58)

recycling endosome


A second secretory pathway found mainly in cells specialized for secreting products rapidly on demand—such as hormones - neurotransmitters - or digestive enzymes—in which soluble proteins and other substances are initially stored in secretory vesicles for later release. (Figure 13–62)

regulated secretory pathway


Monomeric GTPase responsible for regulating COPII coat assembly at the endoplasmic reticulum membrane.

Sar1 protein


Membrane-enclosed organelle in which molecules destined for secretion are stored prior to release. Sometimes called secretory granule because darkly staining contents make the organelle visible as a small solid object. (Figures 13–65)

secretory vesicle


Members of a large family of transmembrane proteins present in organelle membranes and the vesicles derived from them. SNAREs catalyze the many membrane fusion events in cells. They exist in pairs—a v-SNARE in the vesicle membrane that binds specifically to a complementary t-SNARE in the target membrane.

SNARE proteins (SNAREs)


Small neurotransmitter-filled secretory vesicle found at the axon terminals of nerve cells. Its contents are released into the synaptic cleft by exocytosis when an action potential reaches the axon terminal.

synaptic vesicle


Transmembrane SNARE protein - usually composed of three proteins and found on target membranes where it interacts with v-SNAREs on vesicle membranes.



Face on the other (far) side.

trans face


Network of interconnected tubular and cisternal structures closely associated with the trans face of the Golgi apparatus and the compartment from which proteins and lipids exit the Golgi - bound for the cell surface or another compartment.

trans Golgi network (TGN)


Uptake of material at one face of a cell by endocytosis - its transfer across a cell in vesicles - and discharge from another face by exocytosis. (Figure 13–58)



Cell-surface receptor for transferrin (a soluble protein that carries iron) that delivers iron to the cell interior via receptor-mediated endocytosis and recycling of the receptor–transferrin complex.

transferrin receptor