Overview the cell structure.

Cells are the smallest structural and functional units of an organism. Which means an organism can consist of a single cell or multiple cells. Usually cells are microscopic which means they can not be seen with the naked eye. There two types of cell. Including prokaryotic (simple structure with no membrane bound organelles) and eukaryotic (complex structure with membrane bound organelles) cells. Both cells however have a cell membrane which holds and separates the cell from its external environment, a cytoplasm which is all of the cell material enclosed by the membrane and a nucleiod containing genetic material which is the DNA. While prokaryotic cells are usually single called organisms such as bacteria, eukaryotic cells are usually multicellular organisms. The cell structure and function is usually described using the eukaryotic cell. The nucleus contains the DNA which dictates cell replication. The DNA consists of chromatin which is the tangled spread form of DNA in the nuclear membrane. The nucleoulus produce ribosomes which have the function of synthesis of proteins. Outside the nucleus the cytoplasm contains all other cell organelles floating in its fluid. Ribosomes after production from the nucleus are released into the cytoplasm and either float or attach to the endoplasmic reticulum. There are two type of Endoplasmic reticlum (ER). The rough and smooth ER. Ribosomes attach to the rough ER. The ER is a membrane enclosed passage way for transport of materials eg proteins synthesised by the ribosome. These proteins synthesised are released in visicles and taken up by the Golgi apparatus (also known as Golgi body). The Golgi modifies these proteins to structures recogniseable and useable by the cell. This is typically by folding or addition of other substances such as lipids or carbohydrates. Vacuoles store liquid (typically water) in the cell. The mitochondrion is referred to as the power house of the cell because it is responsible for production of ATP molecules through cellular respiration and this powers all the activities of the cell. Lysosomes are responsible for lysis. They engulf damaged or worn out cell organelles or excretory products and break down the cellular debris. Cells also have threadlike microfilaments made of proteins and microtubles which are thin hollow tubes together called a cytoskeleton which maintains the cell’s shape. If a cell is a plant cell, it would contain the cell wall for structure and rigidity and the chloroplast that houses chlorophyll for photosynthesis. Some cells are very unique and contain organelles not typically found in every cell. These structures include flagellum, cillium etc.