DNA and the roles of
water in organisms
A quick review of biomolecules
The DNA molecule
►
►
►
►
Each chromosome is made up of
thousands of genes in a long chain.
Genes carry the genetic information that
affects how we grow and what we look
like. (Example: eye color, skin, etc.)
The long chain is made up of
deoxyribonucleic acid
DNA belongs to a complex group of
biological molecules called a nucleotide
A nucleotide molecule
►
►
►
A single nucleotide is made up of three molecules: a phosphate,
a sugar, and a base
The sugar and phosphate molecules join up to form the
backbone
The bases are attached to the sugar molecule
The structure of DNA
Base Pairing
►
Each base is held together by weak
bonds. There are four different bases:
►
Adenine (A)
►
Thymine (T)
►
Cytosine (C)
►
Guanine (G)
►
Adenine always pairs with Thymine
►
Cytosine always pairs with Guanine
►
Although the bonds are weak, there are many of them. So altogether they keep the
double helix in shape.
The role of water in organisms
Why do we need it?
Water as a solvent
► Circulatory system
► Digestive and
excretory
► Lymphatic system
Water in the
circulatory system
Blood plasma (the liquid
portion of the blood) is made
up of 90% water
Transports carbon dioxide,
glucose, proteins, and
hormones and vitamins to all
parts of the body
Has a diluting effect
Water in the
digestive
and
excretory
system
Creates saliva
Dissolves biomolecules,
Allows the body to absorb and assimilate
substances
Flushes out toxins and waste (urea, used
hormones, drugs, dead blood cells)
Helps regulate body temperature and
water potential
Transport
substance in
plants
►Water molecules
clump together
(cohesive)
►Water molecules are
adhesive
► water sticks to xylem
vessels like a mountain
climber
Nutrient uptake
Water dissolves minerals
so that plants can take
them up through the
xylem
Phloem transports glucose
molecules from the leaves
throughout the plant for
storage or use
Temperature
regulation
►
Organisms can use
evaporation to cool down
►
It takes a lot of energy
before organisms freeze
Ecosystem
stabilization
►
Water can absorb a lot
of heat without
damaging the
enzymes/ proteins in
the cell
►
Organisms are less likely
to be affected by
mild/moderate
changes in
temperature
The End.