Download An Introduction to Metabolism

An Introduction to
Metabolism
• In order to stay alive, living things
must capture, store and use energy.
Without energy, work cannot be
done and life comes to an end.
• Energy is the capacity to do work
• Work is the transfer of energy from
one body or place to another
• Although we can see growth and
movement (etc.), all work is done on
a molecular level (means that
everything that happens on the
outside, happens because of what is
going on at the molecular level).
• Through chemical reactions, cells
manage materials and energy to
keep us alive.
• Sugar possesses chemical
energy. Glucose – Potential
energy of life
• Our bodies can break down
carbohydrates (catabolic
reactions) and build new
material such as DNA from
nucleotides (anabolic reactions).
• The sum of all the anabolic and
catabolic reactions occurring in
a body is called metabolism.
Energy
• Energy exists in many forms:
chemical, electrical, nuclear,
heat, light, mechanical
• 2 types of mechanical energy:
1) kinetic (moving objects), 2)
potential (stored)
Diver Example
• A diver on a platform
has potential energy
because of gravity.
• When he dives he will
fall and gain speed
(gaining kinetic
energy)
• * kinetic energy is
energy possessed by
moving objects
• While he is falling, potential
energy is converted to kinetic
energy.
• Energy in the universe is not
created or destroyed, it can
only be changed from one form
to another (First law of
Thermodynamics).
• Most times, organisms get one type
of energy and convert it to another.
Plants take in light in
photosynthesis, along with water and
carbon dioxide and change it to
glucose (chemical potential energy).
• Animals eat plants to get glucose.
Then, they perform cellular
respiration that takes chemical
energy in glucose and makes ATP.
Chemical Reactions
• In a chemical reaction the bonds
between reactant molecules must be
broken and the bonds between
product molecules must form.
• Energy is absorbed when reactant
bonds break and energy is released
when product bonds form.
• The amount of energy needed to
break the reactants’ bonds is called
activation energy.
• If activation energy is provided,
reactants will reach the transition
state.
• The transition state is when (in a
chemical reaction), the bonds within
the reactants are breaking and the
bonds between products are
forming.
Endothermic and
Exothermic Reactions
• Energy absorbing reactions are
called endothermic reactions
• Endothermic - chemical
reaction in which the energy of
the products is more than the
energy of the reactants
• Energy releasing reactions are
called exothermic reactions
• Exothermic - chemical reaction in
which the energy of the products is
less than the energy of the reactants
• The universe is lazy, it prefers states
that require less energy. So
exothermic reactions happen often.
Why do Endothermic
Reactions Happen?
• These types of reactions occur often
in living organisms (heat, light,
photosynthesis)
• It would seem that exothermic
reactions would happen all the time
since the products require less
energy than the reactants (less
energy state more favorable), but
this is not always the case.
• Why not?
• Entropy - measure of randomness or
disorder in a collection of objects or
energy
• Entropy increases when disorder
increases.
• As substances become more
liquid/gaseous, complex molecules form
simpler molecules, things move from high
concentration to low concentration, this
increases entropy.
• Energy and entropy both affect
whether a chemical reaction
will take place.
• Products with the least energy
requirements are favored
• The universe favors an increase
in entropy
• See p. 61 table 2
• Readings P. 58-68
• Questions: P. 68 1,2,3,4
• Questions on handout