Structure of the Nucleus, Endoplasmic Reticulum, Ribosomes, Assignment

Structure of the Nucleus, Endoplasmic Reticulum, Ribosomes, Mitochondria, Golgi Dody, and Lysosomes - Assignment Example The main function of the cell is to control the expression of proteins (as directed by DNA and RNA). The nucleus itself is a membrane-bound organelle, which means that it is slightly separated by a thin membrane from the rest of the cell components (Tortora & Derrickson, 2008). However, this poses a challenge as messages need to be carried from the enclosed DNA found in chromosomes to the rest of the cell, which is why there are nuclear pores to allow the passage of water-soluble molecules (Campbell & Reece, 2005). The chromosomes themselves are mostly found tightly-packed as chromatin (except during replication), and this function allows the huge amount of human DNA to be contained within each cell (Campbell & Reece, 2005). The structure of these chromosomes changes throughout the cell cycle, particularly relating to cell division. During mitosis or meiosis (cell division), chromatin structures become more condensed and as a result of this change in structure, transcription stops. D uring mitosis, structures known as microtubules form, anchoring the chromatid to the cell wall. This attachment is what allows the cell to divide, splitting sister chromatids in two to form two haploid daughter cells (Campbell & Reece, 2005).... The ER itself is generally split into two sections, known as the rough endoplasmic reticulum and the smooth. The rough ER plays a part in the synthesis of proteins, which is why its surface is covered in ribosomes involved in the process (Tortora & Derrickson, 2008). The ribosomes themselves are bound to the rough ER on a transitory basis, depending on the signal from the nucleus (Tortora & Derrickson, 2008). In fact, the reason that the rough ER is so-called is because the fact that it is studded with these ribosomes makes it look rough under an electron microscope (Tortora & Derrickson, 2008). The ribosomes themselves only bind to the rough ER as required by the cell, and are associated with the initialization of protein-synthesis for part of a secretory pathway (Tortora & Derrickson, 2008). The smooth ER is involved in the synthesis of lipids required by the cell. It is the increased surface area created by the smooth ER that allows the action of enzymes involved in lipid and ster oid synthesis. Each part of the ER thus has a distinct function in regulating cell behavior. Ribosomes Ribosomes are found within all living cells and are primarily involved in protein synthesis, also known as translation (Tortora & Derrickson, 2008). To do this, the ribosomes link together amino acids (found within the cell) to a template specified from messenger RNA (mRNA). This message, in turn, has come from the DNA code found within the nucleus. There are two subunits which comprise a ribosome; the small unit which reads the mRNA template, and the larger unit which anchors small amino acid units together to create a larger, fully formed protein (Campbell & Reece, 2005).