cells and orgenelles reference 1

cells and orgenelles reference 1 - Cells and Organelles...

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Cells and Organelles There are two main types or categories of cells: prokaryotic cells and eukaryotic cells . Both of these types of cells have several things in common. All cells are surrounded by a plasma membrane , which is made of a double layer (a bilayer ) of phospholipids. Within this membrane, is the cytoplasm which is composed of the fluid and organelles of the cell. Bacteria (Kingdom Monera) are prokaryotes . They do have DNA , but it is not organized into a true nucleus with a nuclear envelope around it. Also, they lack many other internal organelles such as mitochondria and chloroplasts. You are pointing to the Organisms in the other four kingdoms are eukaryotes . Their DNA is organized into a true nucleus surrounded by a nuclear envelope which consists of two bilayer membranes. The nucleus of eukaryotic cells contains the genetic material which chemically directs all of the cell’s activities. Usually this is in the form of long strands of chromatin made of DNA and affiliated proteins. When a cell is getting ready to divide, the chromatin coils and condenses into individual, distinguishable chromosomes . Because the nuclear envelope consists of two bilayer membranes, there is a space between these two membranes called a lumen . Branching off from and continuous with the outer membrane of the nuclear envelope is a double walled space which zigzags through the cytoplasm. This is the endoplasmic reticulum ( ER for short) and its central space or lumen is a continuation of the lumen between the membranes of the nuclear envelope. There are two kinds of ER: smooth ER and rough ER . Typically ER closer to the nucleus is rough and that farther away is smooth. Smooth ER is a transition area where chemicals like proteins the cell has manufactured are stored in the lumen for transportation elsewhere in the cell. Pieces of the smooth ER called vesicles pinch off from the smooth ER and travel other places in
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This note was uploaded on 11/05/2010 for the course BIOL 211 taught by Professor Paxton during the Fall '10 term at Salem College.

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cells and orgenelles reference 1 - Cells and Organelles...

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