This my biology notes for AS/A Level that helped me to achieve an A on AS biology exam as well as a full UMS. Additionally, it helped me to get predicted an A* this year
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A. An inorganic ion is an ion that does not contain carbon and there are 4 organic ions that
we need to know
EXAM NOTES 1. Iron ions are essential as they can bind oxygen to form
Hemoglobin is the large protein in red blood cells that is responsible for
Carbohydrates consist transporting oxygen around the body. Hemoglobin is made up of four
of oxygen, hydrogen, polypeptide chains
and carbon
2. PO43- attaches to other molecules to form phosphate groups, which are an
essential component of DNA, RNA and ATP. In DNA and RNA, the phosphate
Amylose coils up due to groups allow individual nucleotides to join up (to form polynucleotides)
the formation of
hydrogen bond In ATP, the bonds between phosphate groups store energy. These phosphate
groups can be easily attached or detached. When the bonds between
What makes amylose phosphate groups are broken, they release a large amount of energy, which
can be used for cellular processes. Phosphates are also found
efficient while storing
in phospholipids, which are key components of the phospholipid bilayer of cell
molecules. membranes
1. Branched therefore
3. Ca2+ Strengthens teeth, bones and nerves in animals, and cell walls in plants.
can be rapidly
hydrolysed (to 4. Mg2+ is needed to produce chlorophyl
release glucose)
2. Glucose molecule
could be easily
added or removed
3. Compact so more
(energy / glucose)
can be stored
4. Insoluble therefore
does not affect
osmosis
Properties of triglyceride
dependent upon the
fatty acids they contain
Hydrogen bond forms in
polysaccharides such as
starch, chitin, and
, Properties of water
1. Water is a solvent
Water is regarded as the ‘universal solvent’ due to the polarity of its molecules. As the positive
oxygen atoms in water attract the negative ions, and the negative hydrogen atoms attract the
positive ions. Hence, all polar molecules (molecules containing ions) can dissolve in water, except
for the non-polar molecules such as lipids do not dissolve in water
2. Water has a high specific heat capacity
Water has the highest specific heat on Earth due to the hydrogen bonds between its molecules. As
a result of having high specific heat, water needs a great amount of energy to increase its
temperature and loses a great amount of energy when its temperature decreases. This prevents
large fluctuations in water temperature. This keeps the temperature stable so that organisms do
not have to endure extreme levels of temperature
3. Water has a high latent heat of vaporisation
Due to cohesion between water molecules (caused by hydrogen bond) a large amount of heat
energy is needed to change water from a liquid to a vapour state and it is very effective way of
cooling the body e.g., via sweating. So, the evaporation of water from a surface causes cooling.
4. Water has strong cohesive properties.
Due to hydrogen bonds, water molecules stick together. Individually these are weak but, because
there are many of them, the molecule stick together in a lattice structure and this sticking is called
cohesion. It allows columns of water to be drawn up the xylem vessels in plants
5. Water has high surface tenson
At normal temperature water has the highest surface tension for any liquid except for mercury.
This is because of the cohesion b/w water molecules at the surface produces surface tension.
Hence, the surface of water can support the mass of many organisms and becomes a habitat for
them e.g., pond skaters
2
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