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Using examples, describe the structure of lipids and their role in organisms

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Using examples, describe the structure of lipids and their role in organisms Lipids are a varied group of organic compounds that can be classified into fats, phospholipids, waxes and sterols.1 As they are non-polar molecules, with the exception of phospholipids, they are insoluble in water but soluble in organic solvents such as alcohol and ether. Lipids contain carbon, hydrogen, oxygen and sometimes phosphorus and nitrogen. They are intermediate-sized molecules that do not achieve the giants sizes of polysaccharides, proteins and nucleic acids.2 The triglycerides, which act mainly as energy stores in animals and plants, are a large important group of lipids. They consist of one molecule of glycerol and three fatty acids, as shown below. Fig.1 Triglyceride3 The glycerol molecule is common to all triglycerides and so the properties of different triglycerides depend on the nature of the fatty acids. Fatty aids vary in the length of their chain and in the degree of saturation they show. ...read more.


When choline is acetylated it forms acetyl-choline, a substance which is very important in transmission of nerve impulses. Phospholipids combine hydrophilic properties of the phosphate group with their hydrophobic properties in the fatty part of the molecule. They are therefore said to be bipolar substances and at an interface where water is present the phospholipid molecule align themselves with the phosphate radicles buried in the water and the fatty tails sticking out of the water. Phospholipids are constituents of all animals and plant cells but are present in abundance in nervous tissue, heart, kidney and egg yolk. Phospholipids are soluble in water to some extent and are found in high concentration in the blood when fat stores are being mobilised and when fatty acids are being absorbed in the gut. Fatty acids are absorbed by forming compounds with bile salts, then the bile salts are freed as the fatty acids are converted to phospholipids in the cells of the gut wall.1 The cell surface membrane is the boundary between the cell and its environment and is a double layer of phospholipid molecules. ...read more.


in particular as waxes are good waterproofing agents, often in leaves and in birds.7 Lipids provide electrical insulation as they protect the nerves and help conduct electro-chemical impulses in the form of a myelin sheath.8 Humans in particular rely on fatty adipose tissue for insulation as this has a lower thermal conductivity than other body tissues and so conducts heat more slowly to the surroundings.2 Desert animals such as the kangaroo rat and the camel yield water when triglycerides are oxidised and store fat for its metabolic water content.9 1Biology of the Mammal Second Edition - Clegg & Clegg, 1968 2Biology Second Edition - Boyle & Senior, 2002 3Louisiana State University Department of Biology - http://www.biology.lsu.edu 4University of Tennessee, Knoxville - http://www.utk.edu 5 Plant and Animal Biology Volume 2 - Vines & Rees, 1967 6Earth Systems Science & Policy Institute, California State University, Monterey Bay - http://essp.csumb.edu/ 7University of Tennessee at Martin - http://www.utm.edu 8Wright State University School of Medicine - http://www.med.wright.edu 9Curriculum Press - http://www.curriculumpress.co.uk Biology Viyaasan Mahalingasivam ...read more.

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