Describe the structure and function of the organelles involved in the synthesis and secretion of proteins
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In the nucleus:
The nucleus is the largest, most visible cell organelle. It's function is to store and regulate access to information encoded by DNA, which is packaged in a complex of DNA and proteins called chromatin (part of nucleoplasm-containing chromatin, water and other soluble materials). The nucleus is enclosed by the nuclear envelope, composed of two membranes only tens of nanometres (nm) apart. This envelope is perforated by nuclear pores made of eight large protein molecules arranged in an octagon shape (about nine nm in diameter), where the two membranes merge. These pores allow RNA and water-soluble materials to enter and exit the nucleus. At certain sites, the outer membrane folds out and is continuous with the rough endoplasmic reticulum (RER). The RER, and to a lesser extent the cytoplasmic surface of the nuclear envelope, carry great numbers of ribosomes for protein synthesis. The nucleolus within the nucleus synthesises ribosomal RNA (rRNA) which forms the ribosomes.
The first step of protein synthesis is transcription in the nucleus, which can be divided into three parts;
Initiation RNA polymerase binds to promoter region on DNA and starts to unwind DNA strand from 5' to 3' end.
Elongation RNA polymerase reads the DNA template from 3' to 5' and produces RNA transcript from 5' to 3'...