lipids Flashcards
what is a lipid?
a triglyceride; it is made up of one glyercol bonded to three fatty acid chains via ester bonds
why are lipids not polymers?
they are made up of chemical units not monomers (no repeated units)
what is a monoglyceride?
a glycerol attached to one fatty acid chain via an ester bond
what is the structural formula for glycerol?
H
I
H – C – OH
I
H – C – O H
I
H – C – OH
I
H
what is the hydroxyl functional group in glycerol?
-OH
what are fatty acids made of?
a carboxyl group (-COOH) and a hydrocarbon
what is a hydrocarbon?
a compound only made of hydrogen and carbon
what does R represent in the fatty acid structural formula?
hydrocarbon
what can vary about the R group of fatty acids?
they can be saturated or unsaturated
what is teh difference between saturated and unsaturated hydrocarbons?
saturated means single bonds and unsaturated are double bonds
what does polyunsaturated mean?
more than one double bond in the chain
why can’t triglycerides dissolve in water?
they are non-polar
what can lipids be dissolved in?
ethanol
write a description of a condensation reaction to form a monoglyceride from a glycerol and fatty fatty acid?
the hydroxyl group of glycerol reacts with the carboxyl group of the fatty acid
water is removed to form an ester bond between the glycerol and fatty acid
a monoglyceride has been produced and one molecule of water
what is the test for lipds?
emulsion test
how does the emulsion test work?
add ethanol, shake , add water , shake
reagents are ethanol and water
what is the positive result in the lipids test?
milky white emulsion
what is a phospholipid?
glycerol bonded to two fatty acid chains and a phosphate ion (negative charge)
why can phospholipids be dissolved in water?
a phosphate ion has a negatice charge (polar)
how are phospholipids structured?
head and two tails
what is the head of a phospholipid made up of and what are its properties?
a phosphate ion and glycerol
negative charge
HYDROPHILIC (love water) face outward towards the intracellular and extracellular fluid
what are the tails of phospholipids made of and what are the properties?
fatty acid chains
no charge
not water soluble
HYDROPHOBIC (don’t dissolve in water)
what are cell membranes and organelle membranes made from?
phospholipid bilayer
what is the phospholipid bilayer?
two layers of phospholipids that make up the cell or plasma membrane.
what is a significant point about the phospholipid bilayer?
no charge- so charged ions cannot pass through
what can/ can’t get across a phospholipid bilayer?
small non-polar molecules that are lipid soluble
not polar molecules that can dissolve in water
what are the roles of lipids?
-cell membranes
-source of energy (when oxidised they provide more than twice the energy as the same mass of carbohydrate and release valuable water)
-waterproofing (since they are insoluble)
-insulation (slow conductors of heat and help retain body heat)
-protection
why are triglycerides such a good source of energy?
high ratio of energy- storing carbon-hydrogen bonds to carbon atoms
why are triglycerides good storage molecules?
have low mass to energy ratio, making them good storage molecules because much energy can be stored in a small volume- beneficial to animals as it reduces the mass they have to carry as they move around
what is the benefit of triglycerides being insoluble in water?
being large, non-polar molecules makes them insoluble in water
so their storage does not affect osmosis in cells or the water potential of them
how are triglycerides an important source of water?
as they have high ratio of hydrogen to oxygen atoms, triglycerides release water when oxidised
