Biology - 1.3 - lipids
give 2 examples of a lipid
triglyceride and phospholipid
how is a triglyceride formed?
condensation between 1 glycerol and 3 fatty acid creating an ester bond
what is a use for lipids in organisms
adipose tissue in humans to insulate and prevent damage to major organs
secreted oils to waterproof organisms
part of cell membranes
what are the 2 key parts of an R group
carboxylic group and hydrocarbon chain
what is the structure of a saturated fat
has an R group with no double bonds, only single covalent bonds so straight and stacks well
usually solid at room temperature
what is the structure of an unsaturated fat
R group has 1+ double bonds so kinked, does not stack well so is usually liquid at room temperature
what is a monounsaturated fat
a fat with one double bond in the R group
what do glycerol molecules have three groups of
hydroxyl
why do triglycerides not dissolve in water
they are polar molecules, so are hydrophobic and insoluble
when does an ester bond form?
when a -OH group from glycerol bonds with a -OH group from the -COOH grpup from the fatty acid in a condensation reaction forming an oxygen bridge and one H2O molecule
describe the structure of a phospholipid
1 glycerol molecule bonded to 2 fatty acids and 1 phosphate, phosphate head and fatty acid tails.
is the phosphate in a phospholipid positively or negatively charged
negatively charged, making it polar
is the fatty acid in a phospholipid positively or negatively charged
positively charged, making it polar
is the phosphate group hydrophilic or phobic
hydrophilic because it is polar so dissolves in water
why are phospholipids useful
allow phospholipid bilayers to be created around cells
why are saturated fats usually solid
straight chains with no double bonds between carbon allow for neat and ordered stacking
how do plants store lipids
as oil in seeds, often unsaturated
how are triglycerides useful for insulation
composes adipose layer under skin which prevents loss of heat
part of the myelin sheath, protects nerve impulses and increases speed of transmission
how are triglycerides useful for buoyancy
low density of fat tissue improves flotation ability of animals
how are triglycerides useful for protection
adipose tissue surrounds vital organs such as liver
how are triglycerides useful for energy storage
insoluble in water so can be stored without affecting water potential
store more energy per gram (37kJ compared to 17kJ)
how are triglycerides useful for energy source
oxidised during respiration, abundance of carbon-hydrogen bonds are broken, releases ATP
how do phospholipids create an water impermeable barrier?
hydrophobic core as a result of hydrophobic fatty acid tails, barrier to water soluble molecules.
how does the structure of a phospholipid relate to the function
phosphate heads make contact with water, tails orientate away from water, creates an impermeable membrane
how do phospholipids create glycolipids
can bond with carbohydrates due to structure, useful for cell recognition on cell surface