Lipids +questions

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LIPIDS
STRUCTURE OF A TRIGLYCERIDE
They are made of carbon, hydrogen and oxygen (lower amounts than carbohydrates).
They are made of one molecule of glycerol and three fatty acids attached.
Fatty acids have long tails made of hydrocarbons. All fatty acids consist of the same basic structure but the
hydrocarbon varies, shown by an R group. The long tails contain a lot of chemical energy-a lot of energy is released
when they are broken down: they contain twice as much energy per gram as carbohydrates.
They are insoluble in water due to their hydrophobic tails. This means they don't cause water to enter by osmosis.
This includes fats which are solid at room temperatures.
Oils are liquids.
FUNCTION
Storage of metabolic fuels in adipose tissue of animals and oils in plants.
Heat insulation in hibernating and marine animals.
Buoyancy and waterproofing in aquatic animals.
Triglycerides are made of three fatty acids attached to a glycerol. Fatty acids are acids as they
contain a carboxyl group (-OOH).
GLYCEROL is three carbon compounds.
Fatty acids are a chain of hydrocarbon molecules.
Their function is energy stores, thermal insulators and protecting internal organs.
They are not attracted to water; they are hydrophobic.
Saturated fats (no double bonds): the fatty acids contain as much hydrogen as they can. Each carbon
atom in the fatty acid is linked via neighbouring carbons. The other two bonds are linked to
hydrogen.
Unsaturated fats (one or more double bonds): this is one or more fatty acids in which at least one of the carbon atoms uses
two of its bond link to a neighbouring carbon atom; it only has one bond left for hydrogen atoms.
PHOSPHOLIPIDS
This is like a triglyceride in which one of the fatty acids are replaced by a phosphate
group. The fatty acid tails of a phospholipid are hydrophobic; however, the
phosphate heads are hydrophilic. This is because the phosphate group has a
negative charge which is attracted to the positive electrical charge on the hydrogen atoms. In water, this forms a bilayer.
STEROIDS
These are made of cholesterol.
Many of them are hormones.
Cholesterol is a main component of cell membranes as they maintain the fluidity of the membrane.
They have a hydrocarbon ring structure attached to a hydrocarbon tail. It has a polar hydroxyl group attached which
makes it soluble,
QUESTIONS
1. Briefly describe the structure of a triglyceride.
2. What type of bonds joins fatty acids to glycerol in triglycerides?
3. Explain how the structure of a triglyceride is related to its function in living things. (4 marks)

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Describe the structure of a phospholipid. (3 marks)
5. Explain the difference between a saturated fatty acid and an unsaturated fatty acid.…read more

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