Endoplasmic Reticulum and Membrane Proteins

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Flashcards covering key vocabulary related to the Endoplasmic Reticulum and Membrane Proteins.

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40 Terms

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Endoplasmic Reticulum (ER)

A network of membranes found within eukaryotic cells, involved in protein and lipid synthesis.

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Lipid Bilayer

The site of action of some toxins like the cholera toxin.

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Ganglioside GM1

A cell-surface receptor for the cholera toxin on intestinal epithelial cells.

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Cholera Toxin

Enters cells, causing an increase in intracellular cyclic AMP, leading to massive secretion of water and electrolytes into the intestine.

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Adenylate Cyclase (AC)

Activated by the cholera toxin A subunit after it's translocated across the ER membrane, increasing cAMP levels.

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Pore-Forming Toxins (β-PFTs)

Produced by pathogens, damage the cell membrane, leading to leakage and lysis of target cells.

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Endoplasmic Reticulum Lumen

The single internal space enclosed by the ER, topologically equivalent to the exterior of the cell.

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Sorting Signals

Specific amino acid sequences recognized by sorting receptors to direct proteins to their destination.

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Sorting Receptors

Function catalytically, returning to their origin after each round of targeting.

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Golgi Apparatus

Receives lipids and proteins from the ER, modifies them (commonly glycosylation), and dispatches them to various destinations in transport vesicles.

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KDEL

A translocation signal within the cell.

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Rough Endoplasmic Reticulum (RER)

Part of the ER with ribosomes attached, giving it a rough appearance; synthesizes proteins destined for the cell surface, ER, lysosomes, Golgi, or secretion.

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Smooth Endoplasmic Reticulum (SER)

Part of the ER with a more tubular appearance and no ribosomes; synthesizes lipids, including cholesterol and phospholipids, and is involved in detoxification.

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Microsomes

Small vesicles formed when the ER fragments during cell disruption.

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Rough Microsomes

Microsomes derived from the rough ER, lined with ribosomes on their outer surface.

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Smooth Microsomes

Microsomes drived from the smooth ER, lacking ribosomes.

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Unfolded Protein Response (UPR)

Feedback mechanism from the rough ER to the nucleus in response to problems in protein synthesis and folding.

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Cytochrome P450

A large family of enzymes in the smooth ER that catalyze reactions to transform water-insoluble drugs or metabolites into water-soluble molecules.

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Sarcoplasmic Reticulum

Specialized smooth ER in muscle cells that sequesters and stores Ca2+.

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Transmembrane Proteins

Proteins that extend through the lipid bilayer, having hydrophobic regions that pass through the membrane and hydrophilic regions exposed to water.

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GPI Anchor

A way membrane proteins are anchored to the lipid bilayer via a covalently bound lipid.

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Apical Surface

The surface of epithelial cells confined with certain plasma membrane enzymes and transport proteins.

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Basal and Lateral Surfaces

Other surfaces of epithelial cells confined with certain plasma membrane enzymes and transport proteins.

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Signal Peptide

Directs the protein into the ER where they fold.

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Post-translational Modifications (PTM)

Modifications to proteins after translation, such as glycosylation, disulfide bond formation, and GPI anchor addition.

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Na+, K+, HCO3

Key ions involved in the massive secretion caused by cholera toxin, leading to diarrhea.

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β-barrel structure

Formed by β-PFTs after oligomerization, creating a channel in the lipid bilayer.

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Transitional ER

The part of the ER that transports lipids and proteins to the Golgi apparatus.

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ER Lumen

Continuous with the nuclear membrane, forming the secretory pathway.

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Glycosylation

A common modification of lipids and proteins in the Golgi apparatus.

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Calsequestrin

Ca2+-binding protein in the smooth ER for Ca2+ storage

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Calmodulin

Ca2+-binding protein in the smooth ER for Ca2+ storage

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Myofibril contraction

Triggered by the release and reuptake of Ca2+ by the sarcoplasmic reticulum.

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ATP production

Membranes of mitochondria or chloroplasts are involved in this process. ~75% or mass is protein (enzymes are proteins).

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Cell-surface receptors

Usually transmembrane proteins that bind ligands in the extracellular space and transduce intracellular signals on the opposite side of the plasma membrane.

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Palmitic acid

A saturated 16-carbon fatty acid, to a cysteine (Cys) side chain of the protein.

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Enterocytes

Epithelial cells lining the gut.

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7 TMDs

Second most common protein transmembrane domain. GPCRs.

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Bilirubin

Bilirubin is transported within the hepatocyte to the smooth endoplasmic reticulum, where its carboxyl groups are conjugated with glucuronic acid.

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Lipid Biomass

The ER therefore has a major influence on cellular lipid biomass and balances the production of different lipid categories, classes, and species.