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CHEMISTRY AND LIFE
One unromantic but productive
way of viewing life is to see it as a
set of coordinated chemical
reactions.
This leads to an obvious question –
What determines which chemical
reactions are possible?
CHEMICAL REACTIONS
Whether a chemical reaction will or won’t occur under
particular conditions is determined by the laws of
thermodynamics.
Keeping it simple -
•If the overall amount of order is decreased by a reaction, the
reaction is favoured
•Generally, if energy is released in a reaction, the reaction is
favoured
The Direction of Spontaneous Reactions
(and what it takes to go the other way)
Life Requires Lots of Unfavourable Reactions – How Is This
Possible?
By coupling favourable to
unfavourable reactions.
favorable
reactions
unfavorable
reactions
The “Nature of Life” – Coupling Favourable to Unfavourable
Reactions
ATP – LIFE’S
ENERGY
CURRENCY
ATP =
Adenosine
Triphosphate
Energy is released
when ATP is
hydrolyzed (broken
down by water) to
ADP.
ATP is restored
from ADP and an
input of energy.
ATP’s energy is
used to drive
endergonic
(energy-requiring)
reactions.
ENZYMES SPEED UP CHEMICAL REACTIONS
Enzymes are biological catalysts – substances that speed a reaction
without being altered in the reaction.
Most enzymes are proteins.
Enzymes are essential for life.
Model of the surface of an enzyme.
Enzymes
Lower a
Reaction’s
Activation
Energy
ENZYME ACTION

http://highered.mcgrawhill.com/sites/0072495855/student_view0/cha
pter2/animation__how_enzymes_work.html
The Fit Between Enzyme and Substrate is Critical and Precise
Hexokinase,
an enzyme
(blue),
binding its
substrate,
glucose
(yellow).
ENZYME DEFICIENCY AND HEALTH
Most genetic disorders are due to a deficiency in enzyme function.
This archival photo shows three children with the enzyme deficiency
that causes phenylketonuria.
What is it?
Phenylketonuria (PKU)
is a hereditary disease
that is caused by the
lack of a liver enzyme
required to digest
phenylalanine.
Phenylalanine is an
amino acid that is most
commonly found in
protein-containing foods
such as meat, cow's
milk, over the counter
infant formulas (both
regular and soy) and
breast milk.
Signs & Symptoms
Newborns affected by PKU usually do not
show any signs of the disease at birth. But
within the first few weeks of life they begin to
show neurologic disturbances such as epilepsy.
Signs also include skeletal changes such as a
small head, short stature, and flat feet. PKU
sufferers may also have a skin disorder called
eczema.
Long Term Effects
PKU-affected children who are not diagnosed
and do not eliminate phenylalanine from the
diet will suffer from irreversible brain damage
and mental retardation. Properly treated
individuals should live a normal, healthy life.
Treatment
Treatment of PKU is the elimination of
phenylalanine from the diet. Phenylalanine is
commonly found in protein-containing foods
such as meat. Babies who are diagnosed with
PKU must immediately be put on a special
milk/formula substitute. Later in life, the diet
is mainly vegetarian.

A phenylketonuria (PKU)
test is done to check
whether a newborn baby
has the enzyme needed to
use phenylalanine in his or
her body. Phenylalanine is
an amino acid that is
needed for normal growth
and development. If a
baby's body does not have
the enzyme that changes
phenylalanine into another
amino acid called tyrosine,
the phenylalanine level
builds up in the baby's
blood and can cause brain
damage, seizures, and
mental deficiencies.
Enzyme Activity is Often
Regulated
Feedback inhibition - a
common form of enzyme
regulation in which the
product inhibits the enzyme .

Temperature and pH effect enzyme action

Temperature and pH effect enzyme action

Enzyme and substrate concentrations