Metabolism
Today we will study concepts on energy and metabolism
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The concept of energy and types of energy.
The laws of thermodynamics.
Review of endergonic and exergonic reactions.
The molecule of ATP as an energy carrier.
The concept of Metabolism and metabolic pathways.
The role of enzymes in metabolic pathways and how
they work.
Energy is defined as the capacity
to do work.
All organisms require energy to
stay alive.
Energy makes change possible
„
Kinetic energy is energy
that is actually doing
work
„
Potential energy is stored
energy
„
Chemical energy is the energy
stored in the bonds of chemical
compounds such as sugars and
lipids.
„
Electrical energy
„
When you turn your car on, your engine transform
chemical energy (gasoline) to kinetic energy.
„
When you walk, you transform chemical energy (ATP)
into kinetic energy.
„
When you turn the light on, you transform electrical
energy into light or radiant energy.
„
The part of physics that studies energy transformations
is called Thermodynamics.
Two laws govern energy conversions
First law of thermodynamics :
Energy cannot be created or destroyed it is simply
transformed from one type to another.
Second law of thermodynamics
„
Energy conversions are not 100% efficient, some
energy is always lost as heat
„
Does this law apply to the car conversion we
mentioned earlier? Explain!
Chemical reactions either store or
release energy
„
Cells carry out thousands of chemical reactions.
Some of these reactions are endergonic, some of
these reactions are exergonic. The sum of these
reactions constitutes cellular metabolism.
Review
An endergonic reaction is:
A reaction that requires energy.
An exergonic reaction is:
A reaction that releases energy
ATP shuttles chemical energy within
the cell
„
In cellular respiration, some energy is stored in
ATP molecules
„
ATP powers nearly all forms of cellular work
„
ATP molecules are the key to energy coupling
„
When the bond joining a phosphate group to the
rest of an ATP molecule is broken by hydrolysis,
the reaction supplies energy for cellular work
Phosphate
groups
Adenine
Hydrolysis
Energy
Ribose
Adenosine triphosphate
Adenosine diphosphate
(ADP)
Figure 5.4A
ATP shuttles chemical energy
within the cell
„
„
„
In cellular respiration, some energy is stored in
ATP molecules
ATP powers nearly all forms of cellular work
ATP molecules are the key to energy coupling
„
When the bond joining a phosphate group to the
rest of an ATP molecule is broken by hydrolysis,
the reaction supplies energy for cellular work
Phosphate
groups
Adenine
Hydrolysis
Ribose
Adenosine
triphosphate
Energy
Adenosine
diphosphate
(ADP)
ATP synthesis: Energy is stored in ATP
energy
ATP
ADP
phosphate
ATP breakdown: Energy of ATP is released
energy
ATP
ADP
phosphate
The ATP cycle
Hydrolysis
Energy
from
exergonic
reactions
Dehydration
synthesis
„
Energy for
endergonic
reactions
„ The great number of exergonic and
endergonic reaction couple forming
metabolic pathways or organized series
of chemical reactions.
How Do Cells Control Their
Metabolic Reactions?
„
„
„
Enzymes are biological catalysts
Enzymes are of a proteic nature
The structure of enzymes allows them to
catalyze specific reactions
What is the role of enzymes?
Catalysts speed up the rate of the reaction because
they reduce activation energy needed for the
reaction to initiate.
How does it work?
A given chemical reaction requires a certain
amount of energy of activation (like a push) that
takes a certain amount of time to accumulate. If
this amount of energy is reduced, the amount of
time needed is also reduced. Enzymes reduce the
energy of activation.
high
activation energy
without
catalyst
energy
content
of
molecules
activation energy
with catalyst
reactants
products
low
progress of reaction
„
The activity of the enzyme is influenced by
its environment. This includes temperature,
pH, salinity, etc…
„
Some enzymes require some additional
element to work. These are called “cofactors”. For example, vitamins are very
common co-factors. Many trace elements
importance is due to the fact that they work
as enzymatic co-factors.