Lecture 25 Part One

Front

What are BAR domains?

Back

BAR domains are domains consisting of coiled coils that form long, thin, curved dimers with a positively charged concave surface. They assemble into crescent-shaped scaffolds and favor membrane curvature.

Front

What are septins and their functions?

Back

Septins are a family of GTP-binding proteins that polymerize at curved regions of the plasma membrane. They participate in cell division, exocytosis, phagocytosis, and apoptosis, and have an amphipathic helix important in vesicle trafficking and neurotransmitter release.

Front

What are fusion proteins?

Back

Fusion proteins mediate the specific fusion of two membranes by bringing about specific recognition and a transient local distortion of the bilayer structure.

Front

What are SNARE proteins?

Back

SNAREs (snap receptors) are a family of proteins. v-SNAREs are located on the cytoplasmic face of the intracellular vesicle, while t-SNAREs are on the target membrane with which the vesicle fuses.

Front

How do nonpolar and polar compounds cross membranes?

Back

Nonpolar compounds can dissolve in the lipid bilayer and cross a membrane unassisted, while polar compounds and ions require a specific membrane protein carrier.

Front

What is membrane potential (Vm)?

Back

Membrane potential, Vm, is a transmembrane electrical gradient that occurs when ions of opposite charge are separated by a permeable membrane. It produces a force that opposes ion movements that increase Vm and drives movements that reduce Vm.

Front

What is an electrochemical gradient?

Back

An electrochemical gradient (electrochemical potential) determines the direction in which a charged solute moves across a membrane. It is composed of the chemical gradient and the electrical gradient (Vm).

Front

What are passive and active transporters?

Back

Passive transporters facilitate movement down a concentration gradient, increasing the transport rate (passive transport or facilitated diffusion). Active transporters move substrates across membranes against a concentration gradient or an electrical potential (active transport).

Front

What are primary and secondary active transporters?

Back

Primary active transporters use energy provided directly by a chemical reaction. Secondary active transporters couple uphill transport of one substrate with downhill transport of another.

Front

What are ion channels?

Back

Ion channels provide an aqueous path across the membrane through which inorganic ions can diffuse at very high rates. They have a gate regulated by a biological signal, show some specificity for an ion, and are not saturable with their ion substrate.