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)
Explain the role of phosphate ions in the body
Componant of:
.DNA
.ATP
.NADP (Topic 5.1)
.cAMP (Topic 6.4)
