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1) A solvent

Importance: many biochemical reactions
occur in water. When a chemical dissolves in
water it is free to move around and react
with other chemicals.

How: water is dipolar so it attracts other
charged particles e.g. ions like Na+, K+, Cl- or
molecules which contain charged particles

Page 2

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How: water breaks down larger molecules
(hydrolysis) e.g.
glycogen glucose.
Reactions making bigger molecules
evolve water e.g.
glucose + glucose maltose + H2O

3) A transport medium

Importance: water dissolves and carries
mineral salts in xylem, it also carries sucrose
and amino acids in phloem. Plasma in our
blood vessels…

Page 3

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4) As a thermos

Importance: most cells only survive within
narrow temperature limits, otherwise their
enzymes can't work well. Many organisms
have water as their habitat for feeding,
breeding, baring young and migrating.

How: the `movement' of water molecules is
restricted because of the H-bonds between
them. A lot of…

Page 4

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5) As an insulator

Importance: ice floats on water's surface,
insulating the water below and allowing
nutrient cycling. Fish can survive the winter!

How: water is most dense at 4 c so frozen
water (ice) will rise up.

6) As a surface for insects to walk on

Importance: some insects…


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