1.3-Lipids + 1.8-Water + 1.9-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
- 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 insulution 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 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 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.
State 4 biologically important properties of water.
Due to polarity and 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 and extracellular fluid.
- Maybe in high or very low concentrations.
Explain the role of phosphate ions in the body.
Component of:
- DNA
- ATP
- NADP
- cAMP
