lipids + water + inorganic ions Flashcards
Describe how to test for lipids in a sample.
- dissolve solid samples in ethanol.
- add an equal volume of water and shake.
- positive result - milky white emulsion forms.
how do triglycerides form?
condensation reaction between 1 molecule of glycerol and 3 fatty acids forms ester bonds.
contrast saturated and unsaturated fatty acids.
saturated contain only single bonds, unsaturated contain C=C double bonds.
saturated are straight-chain molecules with many contact points, unsaturated are ‘kinked’ molecules with fewer contact points.
saturated have a higher boiling point = solid at room temp. unsaturated have lower boiling point = liquid at room temp.
saturated are found in animal fats. unsaturated found in plant oils.
relate the structure of triglycerides to their functions.
high energy:mass ratio = high calorific value from oxidation (energy storage).
insoluble hydrocarbon chain = no effect on water potential of cells and used for waterproofing.
slow conductor of heat = thermal insulation.
less dense in water = buoyancy of aquatic mammals.
describe the structure and function of phospholipids.
amphipathic molecule.
glycerol backbone attached to 2 hydrophobic fatty acid tails and 1 hydrophilic polar phosphate head.
forms phospholipid bilayer in water = component of membranes.
tails can splay outwards = waterproofing.
compare phospholipids and triglycerides.
both have glycerol backbone.
both may be attached to a mixture of saturated and unsaturated fatty acids.
both contain the elements C, H and O.
both formed by condensation reactions.
contrast phospholipids and triglycerides.
phospholipids:
2 fatty acids and 1 phosphate group attached.
hydrophilic head and hydrophobic tail.
used primarily in membrane formation.
triglycerides:
3 fatty acids attached.
entire molecule is hydrophobic.
used primarily as a storage molecule (oxidation releases energy).
are phospholipids and triglycerides polymers?
no.
they are not made from a small repeating unit.
they are macromolecules.
why is water a polar molecule?
oxygen is more electronegative than hydrogen, so attracts the electron density in the covalent bond more strongly.
forms O- and H+.
state 4 biologically important properties of water.
due to polarity and intermolecular H-bonds:
- solvent for chemical reactions in the body.
- high specific heat capacity.
- high latent heat of vaporisation.
- cohesion between molecules.
explain why water is significant to living organisms.
solvent for polar molecules during metabolic reactions.
enables organisms to avoid fluctuations in core temp.
cohesion-tension of water molecules in transpiration stream.
what are organic ions?
ions that do NOT contain carbon atoms.
where are inorganic ions found in the body?
the cytoplasm and extracellular fluid.
may be in high or very low concentrations.
explain the role of hydrogen ions in the body.
high concentration of H+ = low pH.
H+ ions interact with hydrogen bonds and ionic bonds in the tertiary structure of proteins, which can cause them to denature.
explain the role of iron ions in the body.
iron ions bond to porphyrin ring to form the haem group in haemoglobin.
haem group has binding site to transport 1 molecule of oxygen around the body in the bloodstream.
4 haem groups per haemoglobin molecule.
