Summary Edexcel Alevels Unit 1 Topic 1 Biology notes
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Course
Chemistry for biologists
Institution
PEARSON (PEARSON)
Notes for Edexcel Alevel Biology Topic 1: 1- The chemistry of life 2-Monosaccharides 3- Disaccharides 4-Polysaccharides 4- Lipids 5-Proteins. Has tables, definitions and highlighted notes for easy memorization. Contains questions to check your understanding and practice active recall
CHAPTER 1A Chemistry for biologists
THE CHEMISTRY OF LIFE
The properties of water that make it important in biological systems: (discuss how the
properties of water affect living organisms)
1. Water is a polar solvent so many ionic substances like sodium chloride with dissolve in it
2. Water is an excellent transport medium because the dipole nature of water enables many
different substances to dissolve in it
3. As the water cools to 4 degrees it reaches its maximum density as it cools further the
molecules become more widely spaced so ice is less dense than water thus ice floats up
and acts as an insulating layer and prevents the water underneath from freezing as well
this helps organisms in really cold countries survive
4. Water has a high specific heat capacity so the hydrogen bond in the molecules need a lot
of energy to separate so the temperature of large bodies of water doesn't change a lot
throughout the year which makes them good habitats for different organisms
5. Water cant be compressed this is an important factor in many hydraulic mechanisms in
living organisms
6. Water molecules are cohesive and stick together which is vital in the plant transport
system
7. Water molecules are adhesive this is also important in the plant transport systems and in
surface tension
8. Water has a high surface tension because the attraction of water molecules including
hydrogen bonds is greater than the attraction between the water molecules and the air
this is important in the plant transport system and also affects life at the surface of lakes
and ponds
9. Chemicals easily dissolve in water= biochemical reactions can occur in the cytoplasm of
cells
SUMMARY
1- Water is an excellent solvent
2- Water has a high surface tension
3- The water molecule is amphoteric
4- Good tranport medium
5- High specific heat capacity
, Each water molecule is slightly polarized. Water molecules are dipolar because they have
slightly negative (oxygen atom) and slightly positive parts (hydrogen atom). One of the most
important parts of this separation is that water molecules form hydrogen bonds
Water dissolves many non-polar substances These substances may form colloids
Colloid A mixture in which very small particles of one substance are distributed evenly
throughout another substance the solute particles of a colloid are larger than the particles
of the solvent
Particles that are insoluble in water form emulsions or suspensions
Emulsion Tiny droplets of one liquid suspended in another liquid
Suspension A solid mixed with a liquid in which the particles will separate if the mixture
is not constantly moved or stirred
What is a dipole
A dipole exists when a molecule has areas of asymmetrical positive and negative charge.
a molecule that has both negative and positive charges.
The separation of charge in a molecule when the electrons in covalent bonds are not
evenly shared (book)
Polar molecule
. A molecule with a net dipole as a result of the opposing charges (i.e. having partial
positive and partial negative charges) from polar bonds arranged asymmetrically.
A molecule containing a dipole
Water is a polar molecule= it has an unevenly distributed chemical charge
The two hydrogens are pushed towards each other forming a V shaped molecule
Hydrogen= slightly positive charge
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