Lectures 21 & 22 Part Three

Front

What is the endomembrane system?

Back

An interconnected, functionally specialized, and dynamic system of internal membranes in cells.

Front

Where are proteins and lipids synthesized and where do they move through?

Back

Synthesized in the endoplasmic reticulum and move through the Golgi apparatus.

Front

What happens during membrane trafficking?

Back

Proteins are covalently altered, and lipids are segregated into different organelles or concentrated in one of the bilayer leaflets.

Front

What are rafts in cell membranes?

Back

Functionally specialized regions with unique lipid and protein compositions.

Front

What is required for the transbilayer movement of lipids?

Back

Catalysis, as it has a large, positive free-energy change.

Front

What do flippases do?

Back

Catalyze the translocation of phosphatidylethanolamine (PE) and phosphatidylserine (PS) from the extracellular to the cytoplasmic leaflet of the plasma membrane, consuming ~1 ATP per molecule.

Front

What do floppases do?

Back

Move plasma membrane phospholipids and sterols from the cytoplasmic leaflet to the extracellular leaflet, are ATP-dependent, and are members of the ABC transporter family.

Front

What do scramblases do?

Back

Move any membrane phospholipid across the bilayer down its concentration gradient, not dependent on ATP, some require Ca2+.

Front

What is the role of phosphatidylinositol transfer proteins?

Back

Move phosphatidylinositol lipids across lipid bilayers, believed to have roles in lipid signaling and membrane trafficking.

Front

What is FRAP?

Back

Fluorescence recovery after photobleaching, a measure of the rate of lateral diffusion of lipids.