Lipids 2.1.2 Biological Molecules

Triglycerides Buoyancy- Because fat is less dense than water , it is used by aquatic animals to help them stay afloat

Triglycerides Buoyancy

Triglyceride -Consists of one glycerol molecule bonded to 3 fatty acids Glycerol -It is a alcohol -3 Carbon atoms -3 -OH groups Fatty Acids -Have a carboxyl group (-COOH) on the end , attached to a hydrocarbon tail, made of only Carbon and Hydrogen atoms -2-20 carbons long -Carboxyl group ionises into H+ and -COO_ This structure is therefore an acid because it can produce free H+ Phospholipids -same structure as triglycerides except that one of the fatty acids is replaced by a phosphate group.

(h) The structure of a triglyceride and a phospholipid as examples of macromolecules

A triglyceride consists of one glycerol molecule bonded to three fatty acids. A condensation reaction happens between the -COOH group of the fatty acid and the -OH group of the glycerol. Because there are three -OH groups , three fatty acids will bond , hence the name triglyceride. Because it is a condensation reaction , a water molecule is produced , and the covalent bond formed is known as an ester bond.

(i) the synthesis and breakdown of triglycerides by the formation (esterification) and breakage of ester bonds between fatty acids and glycerol

Triglycerides Insulation- Adipose tissue is a storage location for lipids in whales , acting as a heat insulator. Lipid in nerve cells act as an electrical insulator. Animals preparing for hibernation store extra fat

Triglycerides Insulation

Triglycerides Protection- Humans have fat around delicate organs , such as their kidneys , to act as a shock absorber. The peptidoglycan cell wall of some bacteria is covered in a lipid-rich outer coat

Triglycerides Protection

If a fatty acid is saturated this means that there are no C=C bonds in the molecule. If a fatty acid is unsaturated , there is a double bond between two of the Carbon atoms , which means that fewer hydrogen atoms can be bonded to the molecule. A single C=C bond makes a fatty acid monounsaturated , e.g oleic acid. More than one C=C bond makes it polyunsaturated , e.g linoleic acid. Having one or more C=C bonds changes the shape of the hydrocarbon chain , giving it a kink where the double bond is. Because these kinks push the molecules apart slightly , it makes them more fluid. Animal lipids contain lots of saturated fatty acids , which are often solid at 20°C. If there are more unsaturated fatty acids , the melting point is lower.

To include an outline of saturated and unsaturated fatty acids.

Triglycerides

Triglycerides

Triglycerides Energy Source- Triglycerides can be broken down in respiration to release energy and generate ATP. The first step is to hydrolyse the ester bonds , and then both glycerol and the fatty acids can be broken down completely to carbon dioxide and water . Respiration of a lipid produces produces more water than respiration of a sugar.

Triglycerides

Triglycerides Energy Store-Because triglycerides are insoluble in water , they can be stored without affecting the water potential of the cell. Mammals store fat in adipose cells under the skin. One gram of fat releases twice as much energy as 1 gram of glucose.This is because lipids have a higher proportion of hydrogen atoms than carbohydrates , and almost no oxygen atoms.

Triglycerides Energy Store