RIBOSOMES & ENDOPLASMIC RETICULUM.

Ribosomes  Made of ribosomal RNA and protein  Synthesized by nucleolus of cell  Proteins from cytoplasm are brought to nucleus and made with rRNA into large and small subunits of ribosomes  Subunits leave the nucleus and assemble into ribosomes  Carry out protein synthesis

Ribosomes Cont.  Two Types  Bound ribosomes Most proteins made here function in the cytosol  Free ribosomes Most proteins made here are for excretion, insertion into membranes, or packaging in other organelles

Endoplasmic Reticulum (ER)  Endoplasmic: “within the cytoplasm”  Reticulum: “little net”  An organelle in eukaryotic cells that is an extensive network of membranes  ER consists of cisternae (network of membranous tubules)  Two types of ER: SMOOTH and ROUGH

SMOOTH ER  Tasks: synthesis of lipids, metabolism of carbohydrates, detoxification of drugs and proteins, and storage of calcium ions  Named “smooth” because of the lack of ribosomes

ROUGH ER  Cells that secrete proteins produced by ribosomes attach to the ER  “rough” because it is studded with ribosomes  Makes secretory proteins, also is a membrane factory for the cell – it grows by adding membrane proteins and phospholipids to its own membrane