Lipids Flashcards
What is the molecular structure of glycerol
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What is the molecular structure of a saturated fatty acid with 5 carbons
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What is a feature of saturated fatty acids
They have only have single covalent bonds between carbons
What is the structure of a mono-unsaturated fatty acid with 5 carbons in its chain
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What is a feature of a mono-unsaturated fatty acid
It only has one double covalent bond in its chain
What is the structure of a poly unsaturated fatty acid with two double covalent bonds and 5 carbons in its chain
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What is a feature of a poly unsaturated fatty acid
It has more than one double covalent bond between carbon atoms
What do the double covalent bonds in poly unsaturated fatty acids mean
The double covalent bonds are rigid and cause the molecule to bend ( a kink in the chain).
As a result of these double covalent bonds in poly unsaturated fatty acids what does this mean
They can;t pack together as closely making poly unsaturated fatty acids liquid at room temperature.
What are lipids
Molecules containing carbon, hydrogen and oxygen and they are macromolecules that aren’t build from monomers.
What is a property of lipids
They are non-polar molecules as the electrons in the outer shell are evenly distributed creating no partially positive or negative zones.
What are triglycerides
Contain a molecule of glycerol bonded to 3 fatty acid molecules
How does the bonding in a triglyceride occur
A glycerol molecule has 3 hydroxyl groups that can react with the hydroxyl group in the carboxylic part of a fatty acid forming an ester bond. This process is called esterification. A molecule of water is also made, so it’s a condensation reaction. Two more fatty acids then react with two more fatty acids producing a triglyceride.
What happens during digestion of triglycerides
Lipase enzymes break down triglycerides releasing the glycerol and fatty acid molecules. this reaction requires 3 water molecules and is a hydrolysis reaction.
What are features of triglycerides
They are non polar molecules so are hydrophobic and don’t dissolve in water. Because triglycerides contain lots of carbon and hydrogen lots of energy can be released from them.
What are phospholipids
They are comprised of glycerol, two fatty acids and a molecule with a phosphate group
What are the bonds between glycerol and the fatty acids as well as the phosphate group
They are all ester bonds
In a phospholipid what is the hydrophilic and hydrophobic part
The tail (fatty acids) are hydrophobic repelling water.
The head (phosphate group) is hydrophilic and attracts water as it’s charged.
What happens when phospholipids are put in water
the molecules position themselves so that the hydrophilic head groups interact with water molecules while the hydrophobic tails cluster away from the water molecules. So a phospholipid layer is formed.
What do the properties of phospholipids allow
It allows for phospholipids to form membranes
What are sterols
They are steroid alcohols
They are complex with a 4 ring structure and an OH at one end
The OH is polar (hydrophilic), the rest is non polar (hydrophobic)
What is cholesterol
Cholesterol is a sterol so has a hydrophilic OH group and the rest of the molecule is hydrophobic.
What do the hydrophilic and phobic properties allow cholesterol to do
It allows cholesterol to insert themselves into cell membranes as the OH group interacts with the head of phospholipids and the rest with the tails
Where is cholesterol most commonly made
It’s most commonly made in the liver and also intestines
What is the purpose of cholesterol (1)
It’s a common part of membranes, regulating fluidity and is positioned between phospholipids - keeps membranes fluid at low temperatures, and stops them for becoming too fluid at high temperatures
What is the purpose of cholesterol (2)
It makes up vitamin D, which is produced by the skin in response to U.V light and strengthens bones
What is the purpose of cholesterol (3)
It makes up steroid hormones (e.g oestrogen and testosterone)
What is the purpose of cholesterol (4)
It makes up bile which increases the rate of digestion of lipids by lipase.
What are the roles of lipids (1)
Membrane formation and creation of hydrophobic barriers
Hormone production
Electrical insulation necessary for impulse transmission
Water proofing for example bird feathers
What are the roles of lipids (2)
Thermal insulation to reduce heat loss
Cushioning to protect vital organs such as the heart and kidneys
Buoyancy for aquatic animals such as whales
They also have an important role in long term energy storage.
What is the test for lipids
The emulsion test
What are the steps for the emulsion test
First the sample is mixed with ethanol, the resulting solution is then mixed with water and shaken. if a white emulsion forms a layer on top then a lipid is present.
