1.3 Lipids, 1.7 Water, 1.8 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
- lower melting point= liquid at room temperature
- found in plant oils
Relate 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 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 & polyunsaturated 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 function
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 covalent bond more strongly
State 4 biologically important properties of water
Due to polarity & intermolecular H-bonds:
- metabolite/ solvent for chemical reactions in 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 & extracellular fluid
- may be in high or very low concentrations
Explain 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 molecules
Explain role of sodium ions in body
- involved in co-transport for absorption of glucose & amino acids in lumen of gut (topic 2.3)
- involved in propagation of action potentials in neurons (topic 6.2)
Explain role of phosphate ions in body
component of:
- DNA
- ATP
- NADP (topic 5.1)
- cAMP (topic 6.4)
