Lipids Flashcards
What are lipids commonly known as?
Fats or oils.
Why are lipids different from proteins and carbohydrates?
Because they are not polymers formed from long chains of monomers.
What are lipids made from?
A variety of different components.
What do all lipids contain?
Hydrocarbons.
What do the components lipids are made from relate to?
Their functions.
What two types of lipid do you need to know about?
- Triglycerides
* Phospholipids
What is the structure of a triglyceride molecule?
One molecule of glycerol with three fatty acid molecules attached to it.
What is the structure of fatty acid molecules?
They have long ‘tails’ made of hydrocarbons.
What do fatty acids do in water?
They repel water molecules (they are hydrophobic).
What do the hydrophobic fatty acid tails make lipids?
Insoluble in water.
What do triglyceride molecules look like?
image
What do all fatty acids consist of?
The same basic structure.
What varies within all fatty acids?
The hydrocarbon tail (R group).
What are the two types of fatty acids?
- Saturated
* Unsaturated
What is the structure of a fatty acid?
image
Where is the difference between saturated and unsaturated fatty acids?
In their hydrocarbon tails (R group).
What is the difference between saturated and unsaturated fatty acid hydrocarbon tails?
Saturated fatty acids don’t have any double bonds between their carbon atoms whereas unsaturated fatty acids do.
What are saturated fatty acids saturated with?
Hydrogen.
What do the double bonds in unsaturated fatty acids do?
Cause the chain to link.
What do saturated fatty acids look like?
Image
What do unsaturated fatty acids look like?
Image
How are triglycerides formed?
By condensation reactions.
What bond forms when triglycerides are formed by condensation reactions?
An ester bond.
What happens when an ester bond is formed during triglyceride formation?
A molecule of water is released (this is a condensation reaction).
How many times does a condensation reaction occur to form a triglyceride?
Three times.
What does the condensation reaction forming a triglyceride molecule look like?
Image
Which type of lipids are found in cell membranes?
Phospholipids.
What are phospholipids, compared to triglycerides?
Very similar except one of the fatty acid molecules is replaced by a phosphate group.
What does the phosphate group in phospholipids do in water?
They attract water (they we are hydrophilic).
Where is the hydrophilic phosphate group and the hydrophobic fatty acid tail in a phospholipid important?
In the cell membrane.
What does a phospholipid look like?
Image
What do we need to know about triglyceride and phospholipid structures?
How they relate to their properties:
What are some uses of lipids?
- As certain hormones (e.g. testosterone)
* As respiratory substrates (molecules used in respiration to release energy).
What are triglycerides mainly used as?
Energy storage molecules.
Why are triglycerides good as energy storage molecules?
Because the long hydrocarbon tails of the fatty acids contain lots of chemical energy and loads of energy is released when they’re broken down.
What do lipids contain compared to carbohydrates due to the fatty acid tails?
About twice as much energy per gram as carbohydrates.
What happens when you mix triglycerides in water?
They don’t affect water potential of the cell as they’re insoluble in water.
Why is it good that triglycerides don’t affect water potential of the cell?
Because they don’t cause water to enter the cells by osmosis (which would make them swell).
How do triglycerides avoid making water enter the cell by osmosis?
Many triglycerides bundle together as insoluble droplets in cells.
How do triglycerides make insoluble droplets with other triglycerides?
When they bundle together the fatty acid tails face inwards, shielding themselves from water with their glycerol heads.
Why do storage molecules need to be insoluble?
Because if they weren’t they would just dissolve and release what they were storing whenever they came into contact with water.
What do insoluble triglyceride droplets look like?
Image
What do phospholipids do?
They make up the bilayer of cell membranes.
What do cell membranes do?
They control what enters and leaves a cell.
How are phospholipid bilayers structured?
They form a double layer with their hydrophilic heads facing out towards the water on either side and their hydrophobic tails facing inwards.
What do phospholipid bilayers act as?
A barrier to water-soluble substances.
Why are phospholipids good at making up the bilayer of cell membranes?
Because water-soluble substances can’t easily pass through it as the centre of the bilayer is hydrophobic due to the fatty acid tail.
What does a phospholipid bilayer look like?
Image
How do you test for the presence of lipids in a sample?
By doing the emulsion test.
What is the method of the emulsion test for lipids?
- Shake the test substance with ethanol for about a minute.
* Pour the solution into water.
What is the result of the emulsion test for lipids if lipids are present?
The lipid will show up as a milky emulsion (the more lipid there is, the more noticeable the milky colour will be).
What does the emulsion test for lipids look like?
Image
