lipids Flashcards
Functions of lipids
Energy source: can be used in respiration (twice energy per gram as carbohydrates)
Water source
Energy store – insoluble in water so can be stored without affecting the water potential.
Thermal insulation E.g., whale blubber, hibernating animals.
Stores fat soluble vitamins – adipose tissue stores A, D, E and K.
Buoyancy: fat is less dense than water
Cushioning: visceral fat protects organs
Membrane formation and the creation of hydrophobic barriers e.g., lipid-rich coat in bacteria
Hormone production
Electrical insulation for impulse transmission
Waterproofing: e.g., birds’ feathers and cuticle on leaves
elements
carbon, hydrogen and oxygen
what are lipids
macromolecules
macromolecules
complex molecules with a relatively large molecular mass. This means they do not form polymers as they are not monomers.
are lipids polar
no, because of the even distribution of electrons in the outer orbitals where the bonds form.
if lipids are not polar what does this tell us
insoluble in water because they do not attract water molecules, but they do dissolve in alcohol.
Structure of triglycerides
one glycerol molecule with three fatty acids.
glycerol act as backbone of macromolecules
how does triglyceride form
Both molecules have hydroxyl groups (-OH).
The hydroxyl groups interact leading to the formation of three water molecules and three bonds between the fatty acids and glycerol molecule.
These are called ester bonds.
Saturated fatty acids
Fatty acid chains with no double bonds between carbon atoms
all of the carbon atoms have formed the maximum number of bonds with hydrogen atoms.
straight chain
fatty acid chains to pack closely
solid at room temperature
Unsaturated fatty acids
A fatty acid with double bonds between some of the carbon atoms
only one double bond = monounsaturated
two or more double bonds = polyunsaturated
kink
Molecules cannot pack tightly together
liquid at room temperature.
Triglycerides as ideal energy storage molecules
insoluble, do not affect the water potential of cells
release twice as much energy as carbohydrates per gram
bundle together to form insoluble droplets in cells with the hydrophobic tails inwards and the hydrophilic heads outwards allowing them to be transported through
the cell’s aqueous environment
Ratios
1:2:<1
much less oxygen in triglycerides than in carbohydrates
Phospholipids
modified triglycerides
phosphorus, carbon, hydrogen and oxygen
two fatty acids
polar phosphate group is joined to the
third hydroxyl group of the glycerol molecule
amphipathic
How phospholipid structure allows it to perform its functions
dual hydrophilic/hydrophobic structure causes them to form a layer on the surface of water with the phosphate heads in the
water and the fatty acid tails sticking out of the water
surfactants
water-soluble substances cannot easily pass
through.
Sterols
lipid found in cells, but they are not fats or oils
complex ring structures with a hydroxyl (OH) group at one end
amphipathic
The hydroxyl group is polar and therefore hydrophilic ,hydrophobic
