Lipids, Water, Inorganic ions - Biological Molecules 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
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
How do triglycerides form?
condensation reaction between 1 molecule of glycerol & 3 fatty acids forms ester bonds
check google for picture explanation
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.
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.
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)
They are attached to glycerol
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.
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).
