Lipids, Water and 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:
- contains only single bonds
- straight chain molecules have many contact points
- higher melting point = solid at room temp
- 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 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 play outwards = waterproofing
Compare phospholipids and triglycerides.
- both have glycerol backbone
- both may be attached to a mixture of saturated, monounsaturated & polyunsaturated fatty acids
- both contain 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 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.
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 vaporisation
- cohesion and adhesion 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 the 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.
Involved in propagation of action potentials in neurons.
