Lipids Flashcards
Lipids
Biological molecules made of carbon, hydrogen and oxygen that are only soluble in organic solvents such as alcohols
What are the two states lipids can present themselves in?
Fats and oils
What are two common uses of lipids?
Hormones and respiratory substances
What are the two types of lipids?
Triglycerides and phospholipids
What makes lipids insoluble in water?
They contain fatty acid tails that are hydrophobic and contain lots of chemical energy
What is the bond formed in triglycerides?
Ester bond
How many molecules of water are formed in the formation of a triglyceride?
Three molecules due to the three reactions that take place
What state are triglycerides usually found in?
Fats
Saturated lipids (SSS)
Fatty acids that don’t contain any carbon-carbon double bonds and are usually found in animal fats
Unsaturated lipids (DUL)
Fatty acids that contain carbon-carbon double bonds and are usually found in plants
What can occur to saturated lipids?
The molecule is able to bend due to the presence of a double bond and therefore they cannot pack together as tightly
What state are unsaturated lipids usually found in?
Oils since they are liquid at room temperature
Why are triglycerides an excellent energy store?
Because they contain a high ratio of energy-storing carbon-hydrogen bonds to carbon atoms
Why are triglycerides a good storage molecule?
Because they have a low mass to energy ratio so they have a lot of energy stored in a small volume
Why are lipids insoluble in water?
Because they are large and non-polar and so their storage doesn’t affect the water potential of cells
Why are triglycerides an important source of water for organisms that live in dry environments?
Because they have a high ratio of hydrogen-oxygen atoms so they can release water when they are oxidised
What state are phospholipids usually found in?
Waxes
What describes phosphate heads?
Hydrophilic as they love water
What structure do phospholipids form when they are in contact with water?
A polar micelle that presents itself as an insoluble droplet
Where are phospholipids commonly found?
In cell membranes as the hydrophilic phosphate heads are used to remain at the surface to provide structure
What structure do phospholipids form when they are in an aqueous environment?
A phospholipid bilayer
Why is it important that the centre of the phospholipid bilayer is hydrophobic?
Because it makes sure water-soluble substances can’t pass through
Which test is used to detect the presence of lipids?
Emulsion test
What does a positive result of the emulsion test look like?
A cloudy white milky emulsion will form
