Membranous Networks: Trafficking

Membranous Networks: Trafficking

1. Rough ER: labyrinth of flattened sacs/sheets, ribosomes attached to membrane, site of protein synthesis; in lumen-modifications of proteins, proteins then go to golgi. synthesis and processing of secretory proteins. made in cell for export.

2. Smooth ER: Biosynthesis and processing of lipids. bimembrane system. has a lumen, mainly membrane bound, more tubular than rough ER. no ribosomes. functions: synthesis of steroid hormones in endocrine cells

   • function in Liver cells: detoxification of drugs & toxins, release of glucose from glycogen when required
   • function in Muscle cells: sequesting of Ca and regulated release. important in muscle contraction

3. Golgi Apparatus: stacks of flattened disklike membranous cristernae, usually less than 8 in stack, vesicles bud from sides, key site of protein and lipid glycosylation, site of synethesis of complex carbs. modifications of secretory proteins. entry face= cis(forming) face, exit face= trans(mature) face