Topic 1.5 - Lipids Flashcards
What are lipids made of ?
Carbon, hydrogen and oxygen. Like carbohydrates, but they have a higher proportion of hydrogen and lower proportion of oxygen.
What are lipids? Are they soluble or insoluble?
A diverse group of compounds that are insoluble in water but soluble in organic solvents
Why are lipids a good energy sources?
They contain twice the amount of energy as carbohydrates
Where are lipids stored?
Adipose tissue (fat)
What is the function of lipids?
- Source of energy
- Waterproofing - as lipids are insoluble in water
- Insulation - help retain heat
- Protection - stored around delicate organs
Where can fat be used as an electrical insulator?
In the myelin sheath around nerve cells
What are triglycerides made up of?
3 fatty acids bonded to glycerol
What bond forms between the glycerol and fatty acid?
An ester bond
What reaction occurs to form a triglyceride?
Condensation reactions, where H2O is removed and water forms as a product
What happens when triglycerides break down?
They hydrolyse (water is added), producing glycerol and 3 fatty acids
If there are no carbon-carbon double bonds in a fatty acid, what is it called?
Saturated
If there is one carbon-carbon double bonds in a fatty acid, what is it called?
Monounsaturated
If there is two or more carbon-carbon double bonds in a fatty acid, what is it called?
Polyunsaturated
What happens to the lipid produced if the fatty acids have C=C bonds (double carbon-carbon bonds)?
They become oils at room temperature, as the double bond causes the molecule to bend and therefore cannot pack together as tightly.
How is the structure of triglycerides suited to its function?
- Excellent source of energy
- Insoluble (due to being large and non-polar) - does not affect osmosis or water potential
- Provide an important source of water
What are phospholipids made up of?
A phosphate, a glycerol and 2 fatty acids
Is a phospholipid hydrophilic or hydrophobic?
It is amphipathic, both hydrophilic and hydrophobic
Is a phospholipid polar or non-polar?
It is a polar molecule
What do phospholipids play a key role in?
Forming cell membranes as they are able to separate the aqueous environment.
This is done by creating a bilayer of phospholipids, where the hydrophilic head faces the water and the hydrophobic tail is on the inside.
What part of the phospholipid is hydrophilic?
The phosphate group (the ‘head’)
What does ‘hydrophilic’ mean?
‘Water-loving’ - it interacts with water
What part of the phospholipid is hydrophobic?
The fatty acids (the ‘tail’)
What does ‘hydrophobic’ mean?
Water ‘hating’ - does not interact with water so it orientates itself away
What are sterols?
Lipids that are neither fats nor oils
What test is used to identify fats?
The emulsion test
Using the emulsion test, how would you know that the sample contains lipids?
A cloudy-white colour
How is the structure of a phospholipid related to its function?
- They are polar - forms a bilayer in cell membranes to form a barrier between the inside and outside of the cell
- The hydrophilic heads - interacts with the polar molecules, so this allows the passage of proteins, water and many other molecules to go in and out of the cell
- Allows them to form glycolipids (lipids + carbohydrates) - important in cell recognition
How would you conduct a test for lipids?
- For every 2cm cubed there is of the sample, add 5cm cubed of ethanol
- Shake thoroughly to dissolve any potential lipids
- The presence of a lipid will be indicated by the cloudy-white colour formed in tube
