Advanced Cell Exam 2

Plasma Membrane Functions

enclose the cell; define its boundaries; maintain essential differences between cytosol and extracellular environment; contains proteins

Membrane Protein Functions

transport nutrients, metabolites, and ions; anchor the membrane to macromolecules on either side; function as receptors and relay chemical signals; contain enzymes performing catalytic reactions

Transmembrane Membrane Proteins

most are thought to extend across the bilayer as a single alpha-helix, as multiple alpha-helices, or as a rolled-up beta-sheet; some are primarily exposed on one side of the membrane or the other

Lipid-Linked Membrane Proteins

external protein attached to the lipid bilayer by a covalent linkage to a lipid in the inner monolayer or outer monolayer

Monolayer-Associated Membrane Proteins

associated with a phospholipid monolayer by an amphiphilic alpha-helix or via a covalently attached lipid chain

Protein-Attached Membrane Proteins

do not extend into the hydrophobic interior of the bilayer, but are indirectly bound to either face of the membrane by noncovalent interactions with other integral membrane proteins

Integral Membrane Proteins

can be removed by disrupting the bilayer

Peripheral Membrane Proteins

can be released by more gentle extraction that disrupts protein-protein interactions but leave lipid bilayers intact

P-Type Pumps

multipass, phosphorylate themselves during pumping, includes many ion pumps responsible for maintaining gradients.

F-Type Pumps

turbine-like, ATP synthases, use H+ gradient to drive synthesis of ATP from ADP and phosphate

V-Type Proton Pump

turbine-like protein machines constructed from multiple subunits that use energy from the hydrolysis of ATP to pump/transfer H+ into organelles

ABC Transporters

primarily pump small molecules (not ions), two ATP binding domains that drive conformational changes

Aquaporins

channel that facilitates the rapid and selective transport of water across a cell membrane

Action Potential

direct result of properties of voltage gates cation channels

Gated Transport

proteins move between the cytosol and the nucleus through NPCs which function as selective gates

Transmembrane Transport/ Protein Translocation

translocators directly transport specific proteins across a membrane

Vesicular Transport

membrane-enclosed transport intermediates ferry proteins from one compartment to another

Engulfment

movement of proteins from the cytosol into the lysosome in autophagy or used to enclose chromosomes inside the nucleus during envelope reformation after mitosis

Protein Translocation

process of protein movement across membranes

Protein Translocators

multi-subunit protein complexes that mediate protein translocation across membranes

Peroxisomes

small vesicular compartments containing enzymes for oxidation reactions; surrounded by a single membrane, do not contain DNA or ribosomes

Transmembrane Proteins

only partly translocated across the ER membrane and become embedded in it

Water-Soluble Proteins

fully translocated across the ER membrane and are released into the ER lumen

Signal Peptide Role

directs the protein to the ER membrane