1.3 Lipids, 1.7 Water, 1.8 Inorganic Ions Flashcards
Describe test for lipids in a sample
1) Add 2cm3 food sample to test tube
2) Dissolve samples in ethanol
3) Add equal volume of water and shake
4) Positive result: 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 have only single bonds, unsaturated contains C=C double bonds
- Saturated has straight chain molecules, unsaturated has kinked molecules with fewer contact points
- Saturated has higher melting point (solid at room temp), unsaturated has lower melting point (liquid at room temp)
- Saturated fatty acids found in animal fats, unsaturated fatty acids found in plant oils
Relate structure of triglycerides to their function
- High energy:mass ratio = high calorific value from oxidation (energy storage)
- Insoluble hydrocarbon chain = osmotically inactive and used for water proofing
- Slow conductor of heat = thermal insulation e.g. adipose tissue
- Less dense than water = buoyancy of aquatic animals
What is an amphipathic molecule?
Glycerol backbone attached to 2 hydrophobic fatty acid tails and 1 hydrophilic polar phosphate head
Describe structure and function of phospholipids
- Forms phospholipid bilayer in water = component of membranes
- Tails can splay outwards = waterproofing
Compare phospholipids to triglycerides
- Both have glycerol backbone
- Both may be attached to a mixture of saturated, monounsaturated and polyunsaturated fatty acids
- Both contain elements C, H and O
- Both formed by condensation reactions
Contrast phospholipids to triglycerides
- Phospholipids have 2 fatty acids and 1 phosphate group, triglycerides have three fatty acids
- Phospholipids: hydrophilic head and hydrophobic tail, Triglycerides: entire molecule is hydrophobic
- Phospholipids: used primarily in membrane formation, triglycerides: used primarily as storage molecule (oxidation releases energy)
Are phospholipids and triglycerides polymers?
No, they aren’t made from small repeating units. 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 delta-negative (slightly positive charge) and H delta-positive (slightly positive charge)
State 4 biologically important properties of water
- Metabolite/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 reaction
- Enables organisms to avoid fluctuations in core temperature
- Cohesion-tension of water molecules in transpiration stream
What are inorganic ions?
Ions that do not contain carbon atoms
Where are inorganic ions found in the body?
- Found in 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 (acidic) pH
- H+ ions interact with H-bonds and ionic bonds in the tertiary structure of proteins, which can cause them to denature
