a quick question on Biology.

[Kahlua]

During the formation of red blood cells from stem cells, the cells start out with most organelles, including a nucleus and mitochondria. They loose them both during the final stages of formation though, when the cell gets rid of all organelles and becomes a full blown erythrocyte, a fancy word for a red blood cell. Not sure which phase they loose them at, but if you don't need to know it...who cares?

I don't know the answer to the third question...but wikipedia does. Everything you need to know is in there.

The surface of the rough endoplasmic reticulum (RER) is studded with protein-manufacturing ribosomes giving it a "rough" appearance (hence its name). The binding site of the Ribosome on RER is a Glycoprotein receptor called Ribophorin.[2] However, the ribosomes bound to the RER at any one time are not a stable part of this organelle's structure as ribosomes are constantly being bound and released from the membrane. A ribosome binds to the ER only when it begins to synthesize a protein destined for the secretory pathway.[3] Here, a ribosome in the cytosol begins synthesizing a protein until a signal recognition particle recognizes the pre-piece of 5-15 hydrophobic amino acids preceded by a positively charged amino acid. This signal sequence allows the recognition particle to bind to the ribosome, causing the ribosome to bind to the RER and pass the new protein through the ER membrane. The pre-piece is then cleaved off within the lumen of the ER and the ribosome released back into the cytosol.
The membrane of the RER is continuous with the outer layer of the nuclear envelope. Although there is no continuous membrane between the RER and the Golgi apparatus, membrane-bound vesicles shuttle proteins between these two compartments.[4] Vesicles are surrounded by coating proteins called COPI and COPII. COPII targets vesicles to the golgi and COPI marks them to be brought back to the RER. The RER works in concert with the Golgi complex to target new proteins to their proper destinations. A second method of transport out of the ER is areas called membrane contact sites, where the membranes of the ER and other organelles are held closely together, allowing the transfer of lipids and other small molecules.[5][6]
The RER is key in multiple functions:
Lysosomal enzymes with a mannose-6-phosphate marker added in the cis-Golgi network
Secreted proteins, either secreted constitutively with no tag or secreted in a regulatory manner involving clathrin and paired basic amino acids in the signal peptide.
Integral membrane proteins that stay embedded in the membrane as vesicles exit and bind to new membranes. Rab proteins are key in targeting the membrane; SNAP and SNARE proteins are key in the fusion event.
Initial glycosylation as assembly continues. This is N-linked (O-linking occurs in the golgi).
N-linked glycosylation: If the protein is properly folded, glycosyltransferase recognizes the AA sequence NXS or NXT (with the S/T residue phosphorylated) and adds a 14-sugar backbone (2-N-acetylglucosamine, 9-branching mannose, and 3-glucose at the end) to the side-chain nitrogen of Asn.