Biological molecules (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 & 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 solid
- 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 and polyunsaturated fatty acids
.Both contain the elements Carbon,Hydrogen and Oxygen
.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 - (slight negative charge) and Η + (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 t living orrganisms
. 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?
. lons 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 and ionic bonds in tertiar 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 and amino acids in lumen of gut (Topic 2.3)
Involved in propagation of action potentials in neurons (Topic 6.2)
