ORGANELLES

=Organelles= [image:http://i.imgur.com/uWMgEan.jpg?2] An organelle is a specialised subunit within a cell that has a specific function. Most organelles are separately enclosed within their own membrane (lipid bilayers). ==Cell / Plasma Membrane== '''Structure''': [image:http://i.imgur.com/zuV5Wqy.png?4]Outermost layer surrounding animal cells and within cell wall of plant cells. Consists of a double layer of molecules known as phospholipids. '''Function''': It is selectively permeable and controls the movement of substances into and out of the cell. The cell membrane is involved in ''secretion, diffusion, osmosis'' and ''active transport''. ==Cytoplasm== [image:http://i.imgur.com/r5m6WWH.png?7] '''Structure''': A watery solution containing dissolved substances, enzymes and cell organelles. '''Function''': The cytoplasm is the site of many chemical reactions and can act as a buffering solution ensuring appropriate conditions for enzyme function. ==Nucleus== [image:http://i.imgur.com/K3QcLT6.png?1] '''Structure''': Membrane enclosed organelle which contains the cells genetic material and nucleolus. '''Function''': Controls and regulates cell activity. Often contains a dense spot of genetic material (DNA) known as the nucleolus. ===Nucleolus=== [image:http://i.imgur.com/46p3GIB.jpg?2] '''Structure''': The nucleolus is the largest structure in the nucleus. '''Function''': Primarily serves as the site of ribosome synthesis and assembly. ===Plasmids=== [image:http://i.imgur.com/tajUiuz.jpg?1] '''Structure''': A plasmid is a small DNA molecule often found within bacterial cells. '''Function''': It is physically separated from a chromosomal DNA and can replicate independently. ==Mitochondria== [image:http://i.imgur.com/hfdjxzc.jpg?2] '''Structure''': Organelle bound by a double membrane within the cytoplasm. The inner layer contains cristae- folds that increase the internal surface area. '''Function''': Site of cellular respiration; the conversion of chemical energy (glucose) into adenosine triphosphate (ATP-cellular energy). ==Ribosomes== [image:http://i.imgur.com/ASWelzQ.png?1] '''Structure''': Small structures that are either free within the cytoplasm or attached to rough endoplasmic reticulum. These Ribosomes are made up of RNA and proteins and may be . '''Function''': the site of '''translation''' (see genetics notes) phase of '''protein synthesis'''. ==Endoplasmic Reticulum== [image:http://i.imgur.com/qAYeVCm.png?1] '''Structure''': Network of tubes and flattened membrane sacs called ''cisternae'' within the cytoplasm. May be rough (with ribosomes on surface) or smooth (without ribosomes). '''Function''': The Rough E.R. is primarily involved in protein synthesis. This occurs on small structures within the cytoplasm, known as ribosomes. The '''Smooth Endoplasmic Reticulum''' is involved in the transport of proteins, the production of lipids and steroids, the metabolism of carbohydrates and steroids, drug detoxification, etc. ==Golgi Apparatus / Body== [image:http://i.imgur.com/XgBE6bR.png?1] '''Structure''': A series of flattened disc shaped sacs called ''cisternae'' within the cytoplasm, stacked on top of each other which are connected with the endoplasmic reticulum. '''Function''': Stores, modifies and packages proteins, including hormones that are to be excreted. ==Vesicles== [image:http://i.imgur.com/Jz9kMmm.gif?1] '''Structure''': Small organelle within a cell, consisting of fluid enclosed by a lipid bilayer membrane. '''Function''': Vesicles store, transport, or digest cellular products and waste. Vesicles can fuse with the cell/plasma membrane to release their contents outside of the cell. Vesicles can also fuse with other organelles within the cell. ==Lysosome== [image:http://i.imgur.com/EmeVnEI.gif?1] '''Structure''': Membrane sacs which have pinched off from the golgi apparatus, containing enzymes and other chemicals. '''Function''': Packages waste and contains enzymes and chemicals which break it down. ==Cilia== [image:http://i.imgur.com/1xBwGZa.gif?1] '''Structure''': Long hair-like structures protruding the cell membrane. Cells with cilia tend to have very large numbers of them. '''Function''': Assist the cell in movement. Also found on the cells lining the airways (which beat / move rhythmically in order to expel material from the lungs). ==Centrioles== [image:http://i.imgur.com/vfVb4Ib.jpg?2] '''Structure''': Small, barrel shaped organelles within the cytoplasm. Centrioles consist of a series of ''microtubules''. '''Function''': Associated with formation / positioning of spindle fibres during cell division. Also play a role in the special arrangement of the cell and the position of ''flagella'' and ''cilia''. '''Only Found in Animal Cells'''. ==Cell Wall== [image:http://i.imgur.com/fizwq3L.jpg?2] '''Structure''': Semi-rigid structure outside the cell membrane. The cell wall is made of cellulose. '''Function''': Keeps the structure of the cell and limits its volume by preventing excessive fluid intake. '''Only found in plants'''. ==Chloroplasts== [image:http://i.imgur.com/inT59DS.jpg?1] '''Structure''': Organelle bound by a double membrane within the cytoplasm. Chloroplasts contain a green pigment termed ''chlorophyll''. '''Function''': Site of '''photosynthesis'''. Convert energy from the sun into chemical potential energy that can be stored or used for respiration. '''Only found in plants'''. ==Flagellum== [image:http://i.imgur.com/ccqxZyb.png] '''Structure''': Long hair-like structure protruding the cell membrane. Very similar in structure to cilia, except much larger. Cells tend to have only one flagellum (if any). '''Function''': Assists the cell in movement. '''Found in Prokaryotes and some unicellular Eukaryotes'''