Lipids: Roles of Triglycerides | A-level Biology | OCR, AQA, Edexcel

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The key points covered in this video include:

1. Saturated and Unsaturated Triglycerides
2. Triglycerides in Respiration
3. Triglycerides as an Energy Store
4. Other Roles of Triglycerides

Saturated and Unsaturated Triglycerides

Triglycerides are more commonly known as fats and oils. The difference between fats and oils is that fats are solid at room temperature and oils are liquid at room temperature. This difference in state is due to the presence of double bonds between carbon atoms in the fatty acid tail. Fatty acids with hydrocarbon chains that have no double bonds between carbon atoms are saturated. Fatty acids with hydrocarbon chains that have one double bond between carbon atoms are monounsaturated. Fatty acids with hydrocarbon chains that have many double bonds between carbon atoms are polyunsaturated. The carbon double bonds in unsaturated hydrocarbon chains cause the fatty acid tails to bend. This bending pushes the unsaturated triglyceride molecules further apart than the saturated molecules. This weakens the intermolecular forces between the unsaturated triglyceride molecules so they form a liquid at room temperature.

Triglycerides in Respiration

In respiration, biological molecules like glucose are broken down to provide energy. Triglycerides can be broken down into glycerol and fatty acids which are also used in respiration. Triglycerides release lots of energy in respiration due to the large number of carbon hydrogen bonds which are broken down. Triglycerides also provide a good source of water for metabolic reactions. This is because water is released when the components of triglycerides are broken down in respiration.

Triglycerides as an Energy Store

Triglycerides are also excellent molecules for energy storage for a number of reasons: 1. They provide the most energy per unit of mass of any storage molecule. This is useful for animals as it reduces the mass that must be carried around. 2. They are also large and non-polar so are insoluble in water. Therefore they do not affect the osmotic balance of cells in the body.

Other Roles of Triglycerides

Triglycerides also have many other useful properties: Oils repel water so aquatic animals produce oil to waterproof their fur, Fats are used by animals as thermal insulation, Fats are also used by animals to protect internal organs, Fats are less dense than water so they aid in buoyancy for aquatic animals.

Summary

Saturated fatty acids do not contain double bonds between carbon atoms
Monounsaturated fatty acids contain one double bond between carbon atoms and polyunsaturated fatty acids contain many double bonds between carbon atoms
Triglycerides that have saturated fatty acid tails are liquid at room temperature (oils)
Triglycerides that have unsaturated fatty acid tails are solid at room temperature (fats)
Triglycerides have important roles such as:
○ energy sources
○ energy stores
○ waterproofing
○ thermal insulation
○ protection
○ buoyancy

Видео Lipids: Roles of Triglycerides | A-level Biology | OCR, AQA, Edexcel канала SnapRevise