AQA A-Level Biology Topic 1 Summary Notes by Miss Estruch (reselling it cheaper for you guys).
Highly recommend, contains everything you need to know for Biological Molecules with key words that are used in exams markschemes.
This summary contains detail notes for:
Water
Proteins
Lipids
...
MISSESTRUCH 2020 Metabolite
The Structure of Water
Solvent
High specific heat capacity
Water is an incredibly important biological
molecule, which is why about 60-70% of your body Strong cohesion
is water. Large latent heat of vaporisation
Water is a dipolar molecule (di meaning two and
polar referring to charges). Water has an unevenly
distributed charge due to the fact that the oxygen
atom is slightly negative, and the hydrogen atoms
are slightly positive. The delta ( δ ) symbol
indicates a slightly positive/negative on the
diagram.
Five Key Properties of Water
Hydrogen bonds form between different water molecules between the oxygen and a hydrogen atom.
The formation of these hydrogen bonds and the fact that water is dipolar results in 5 key properties of
water:
1. It is a metabolite (e.g. in condensation and hydrolysis reactions).
2. An important solvent in reactions.
3. Has a high heat capacity, it buffers temperature.
4. Has a large latent heat of vaporisation, providing a cooling effect with loss of water through
evaporation.
5. Has strong cohesion between water molecules; this supports water columns and provides
surface tension
MISSESTRUCH 2020
, WATER
Key Terms
Metabolite
3.1 BIOLOGICAL MOLECULES Hydrolysis
MISSESTRUCH 2020 Dipolar
Metabolite
Solvent
Hydrophobic
Water is involved in many reactions, such as photosynthesis,
hydrolysis, and condensation reactions. Hydrophilc
This is one reason why it is essential that approximately
90% of the plasma in the blood is water and the cytoplasm in
cells is largely composed of water.
Solvent
Water is a good solvent, meaning many substances dissolve in
it. Polar, or charged, molecules dissolve readily in water due to
the fact water is dipolar. The slight positive charge on
hydrogen atoms will attract any negative ion solutes and the
slight negative charge on the oxygen atoms of water will
attract any positive ions in solutes. These polar molecules are
often described as hydrophilic, meaning they are attracted to
water.
Non-polar molecules, such as lipids, cannot dissolve in water and are therefore described as
hydrophobic- they are repelled by water.
The fact that so many essential polar substances dissolve in water enables them to be transported
easily around animals and plants, either in the blood or xylem, to cells, they are needed in inside of
the organism.
MISSESTRUCH 2020
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