Lipids
- Created by: Emily Cartwright
- Created on: 09-02-14 10:01
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- Lipids
- Contain:
- Hydrogen
- Carbon
- Oxygen
- Consist of two different molecules: Glycerol and Fatty Acids
- Formed by one molecule of glycerol and 3 molecules of fatty acids
- They are therefore known as triglycerides
- Formed by one molecule of glycerol and 3 molecules of fatty acids
- Fatty Acid structure
- A carboxyl group (COOH)
- A variable length hydrocarbon chain (CH2)n
- There are always an even number of hydrogen atoms (between 2 and 14)
- A methyl group (CH3)
- Fatty acids can be:
- Saturated (Fats mainly found in animals)
- Only single bonds between carbon atoms in the hydrocarbon chain. Every bond has a hydrogen attached, so the lipid is 'saturated' with hydrogen
- They have a high melting point and are solid at room temperature
- A high intake of saturated fats is a contributory factor in heart disease
- They have a high melting point and are solid at room temperature
- Only single bonds between carbon atoms in the hydrocarbon chain. Every bond has a hydrogen attached, so the lipid is 'saturated' with hydrogen
- Unsaturated (Fats mainly found in plants)
- Have more than one double bond in their hydrocarbon chain
- This gives the molecules a kink and they tend not to pack together giving unsaturated fats a more open and oily nature
- They have a low melting point so are liquid at room temperature e.g. plant oils
- This gives the molecules a kink and they tend not to pack together giving unsaturated fats a more open and oily nature
- Have more than one double bond in their hydrocarbon chain
- Saturated (Fats mainly found in animals)
- Formation of a triglyceride
- Three fatty acids bond with a glycerol molecule to form a triglyceride
- There are three condensation reactions releasing three water molecules
- Three ester bonds are formed
- There are three condensation reactions releasing three water molecules
- Triglycerides are non polar so they do not attract water, therefore they are hydrophobic molecules
- Three fatty acids bond with a glycerol molecule to form a triglyceride
- Function of Lipids
- To act as an energy store in cells. A lipid stores twice as much energy as the same mass of carbohydrates, making it a very efficient store
- Lipids are used in seeds to store energy
- Although lipids have a higher energy yield/gram than carbohydrates, they cannot be broken down as quickly for use in respiration, so are used as long term energy stores in animals
- Provide insulation (thermal) against heat loss
- To protect vital organs in animals, e.g. heart and kidneys
- Bouyancy in aquatic animals
- As a source of metabolic water for organisms that live in low water environments e.g. Camels
- Provide a waterproofing layer
- To act as an energy store in cells. A lipid stores twice as much energy as the same mass of carbohydrates, making it a very efficient store
- Emulsion test for lipids/ triglycerides
- 1. Mix the lipid with ethanol
- 2. Pour/decant the mixture into water
- 3. A white emulsion shows that lipid is present
- 2. Pour/decant the mixture into water
- 1. Mix the lipid with ethanol
- Lipids do not dissolve in water but do dissolve in some organic solvents e.g. ethanol and acetone
- Phospholipids
- One fatty acid is replaced by a phosphate group (PO4 3-)
- The phosphate group is ionised which makes is polar, so it attracts water molecules.
- One fatty acid is replaced by a phosphate group (PO4 3-)
- Contain:
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