The Structure and Function of Lipids in Plants and Animals

The Structure and Function of Lipids in Plants and Animals
Lipids are a group of compounds, which possess an oily waxy or greasy consistency. These organic compounds are relatively insoluble in water and tend to be water repelling. An example of this is on leaf surfaces. The waxy cuticle prevents water loss in plants. Lipids are very important substances as they are used as biological fuels, some serve as structural components in plasma membranes and some are hormones. Proteins and carbohydrates can also be converted into fats by enzymes, which can then be stored within cells of adipose tissue. This is useful because when there is plenty of fats the storage capacity will increase to reserve food for times when there is a shortage. Neutral fats are the most abundant lipids in living things. They are found in fats and oils, which are found in plants and animals. Fats are an efficient way to store fuel reserves, since they produce more than double the amount of energy produced by the same quantity of carbohydrate. Neutral fats are made of a glycerol molecule attached to one (monoglyceride), two (diglyceride) or three (triglyceride) fatty acids.
Text Box: Glycerol Fatty Acid Fatty Acid Fatty Acid Triglyceride These fatty acid chains can either be saturated or unsaturated. Wax possesses a similar structure to fats and oils, however they are formed with a complex alcohol instead of glycerol. [image]In the formation of a trigylceride three condensation reactions take place. A condensation reaction is when water is produced in a chemical reaction. When glycerol bonds with the fatty acid, an ester bond is formed and water is released. Fatty is vital factor in neutral fats and phospholipids. In animals about 30 different kinds of lipids are found. Fats, which are saturated, contain the maximum number of hydrogen atoms. Unsaturated fats contain a few carbon atoms, which are double, bonded to each other and are not completely saturated with hydrogen?s. Palmatic acid (Saturated fatty acid) [image] Linoleic acid (unsaturated fatty acid) Lipids, which have a high proportion of saturation, tend to be solids at room temperature such as butter. On the other hand lipids, which have a high proportion of unsaturated fatty acids, are oils and tend to be liquid at room temperature. No matter how saturated, fatty acids produce a large amount of energy when oxidised. As triglycerides are poor conductors of heat, they can prevent heat loss from our skin, as there is a layer of fat underneath our skin. This is very important in aquatic mammals like seals, Whales and walruses. They build up a huge layer of fat to protect them from losing too much heat in the cold arctic environment. As the density of the fat is less then that of water it also provides buoyancy, which enables the animals to stay, near the surface. Fat also absorbs shock. A relatively thick layer of fat cushions organs, which are prone to bumps and shocks like kidneys. Lipids are also a source of metabolic water. During respiration, stored lipids are metabolised for energy, which produces water and carbon dioxide. Stored lipids also provide insulation for animals in the winter to reduce heat loss. Fatty acids can also be converted in to phospholipids, which are important constituents of cell membranes. Text Box: Glycerol Fatty Acid Phosphate group PO43- Phospholipids consist of a glycerol attached to two fatty acid chains and a phosphate group. The phosphate end is negatively charged so it is attracted to water so it is said to be hydrophilic while the fatty acid end is repelled which is said to be hydrophobic. The hydrophobic ends turn inwards in the membrane to form a phospholipd bilayer.

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