Essential Biology 03.1: Chemical Elements and Water
1. What are the four most commonly occurring elements in living things?
Hydrogen, Oxygen, Carbon, Nitrogen
2. State some functions of each of these elements in living things:
a. Iron
Symbol: Fe
Ion: 26
Function(s): used to make chlorophyll , used in photosynthesis as ferredoxin. It also
facilitates the movement of electrons in cells.
a. Sulphur
Symbol: S
Ion: 16
Function(s): It is a reactant for chemosynthetic bacteria (chemoautotrphs).
b. Calcium
Symbol: Ca
Ion: 20
Function(s): It is used in the structure of bones and teeth in animals and can also be used for
blood clotting.
c. Phosphorous
Symbol: P
Ion: 15
Function(s): It is essential for the formation of the phospholipid bilayer. They are also the
active components in ATP molecules and make up part of the backbone of DNA.
d. Sodium
Symbol: Na
Ion: 11
Function(s): Sodium Is essential in generating an action potential for nerve impulses.
e. Potassium
Stephen Taylor
Symbol: K
Bandung International School
Ion: 19
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Essential Biology 03.1: Chemical Elements and Water
Function(s): Potassium also plays a role in nerve impulses and has a strong influence in
osmosis.
3.
In the space below, draw three water molecules attracted to one another by hydrogen
bonding. Include labels to show the polarity of the molecules.
Annotate: How does H-bonding work?
H
Oxygen
H
H
Oxygen
H
Oxygen
Hydrogen bonds
H
H
6. Water has many properties which are essential for life. Complete the table below.
Thermal Properties
Cohesion
Stephen Taylor
Explanation
Significance to living things
Water has a high specific heat capacity. This
means it takes a lot of energy for the
temperature of water to change. This is
because there are so many H-bonds.
Most organisms are adapted to a
narrow range of conditions. The slow
heating and cooling of water are ideal
for these organisms – there is less risk of
extreme changes.
A single hydrogen is not very strong. A large
number of hydrogen bonds is very strong.
Molecules of water stick to each other, and
water stick to other surfaces.
These properties lead to capillary action,
where water will move up xylem against
gravity, and surface tension, where the
surface of water is strong enough to
support insects ad causes drops to form.
Bandung International School
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Essential Biology 03.1: Chemical Elements and Water
Solvent Properties
Water is a good solvent because it is a polar
molecule. It will dissolve polar solutes easily.
Polar attractions cause water molecules
to surround and isolate the solute
molecules.
(include uses as a coolant, medium for metabolic reactions, transport medium)
Stephen Taylor
Bandung International School
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