1.3 Lipids + 1.7 Water + 1.8 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 &
3 fatty acids forms ester bonds
Contrast saturated and unsaturated fatty
acids.
Saturated: ● Contain only single bonds ● Straight-chain molecules have many contact points ● Higher melting point = solid at room temperature ● Found in animal fats
Unsaturated: ● Contain C=C double bonds ● ‘Kinked’ molecules have fewer contact points ● Lower melting point = liquid at room temperature ● 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 & used for waterproofing.
● Slow conductor of heat = thermal insulation e.g.
adipose tissue.
● Less dense than water = buoyancy of aquatic
animals.
Describe the structure and function of
phospholipids.
Amphipathic molecule: glycerol backbone
attached to 2 hydrophobic fatty acid tails & 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, monounsaturated & polyunsaturated fatty acids. ● Both contain the elements C, H, O. ● Both formed by condensation reactions.
Contrast phospholipids and triglycerides.
phospholipids: ● 2 fatty acids & 1 phosphate group attached ● Hydrophilic head & 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?
O is more electronegative than H, so attracts the electron density in the covalent bond more strongly. forms O 𝛿- (slight negative charge) & H 𝛿+ (slight positive charge).
State 4 biologically important properties
of water.
due to polarity & intermolecular H-bonds:
● Metabolite / solvent for chemical reactions in
the body.
● high specific heat capacity.
● high latent heat of vapourisation.
● 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 temperature.
● Cohesion-tension of water molecules in
transpiration stream.
What are inorganic ions and where are
they found in the body?
● Ions that do not contain carbon atoms. ● Found in cytoplasm & extracellular fluid. ● May be in high or very low concentrations.
Explain the role of hydrogen ions in the
body.
● High concentration of H+ = low (acidic) pH. ● H+ ions interact with H-bonds & ionic bonds in tertiary structure of proteins, which can cause them to denature.
Explain the role of iron ions in the body.
Fe2+ bonds to porphyrin ring to form haem
group in haemoglobin.
Haem group has binding site to transport 1
molecule of O2
around body in bloodstream.
4 haem groups per haemoglobin molecule.
Explain the role of sodium ions in the
body.
Involved in co-transport for absorption of glucose & amino acids in lumen of gut (Topic 2.3). Involved in propagation of action potentials in neurons (Topic 6.2).
