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Energy and metabolism
Section 1.3
Energy and metabolism
 Energy is the ability to do work.
Living organisms must continually
capture, store and use energy to
carry out the functions of life.
 Metabolism refers to the sum of all
*anabolic and catabolic processes in a
cell or organism.
 *anabolic means to build, catabolic to
break down
Thermodynamics
 Is the study of energy
 Energy is classified as either:
 Kinetic
 energy possessed by moving objects
 comes in many forms (thermal/heat,
mechanical, electromagnetic and electrical)
 Potential
 stored energy
 ex: gravitational potential energy, and
chemical potential energy
First Law of Thermodynamics:
Energy cannot
be created or
destroyed but
only converted
from one form
into another.
Types of reactions:
1. Exergonic reaction: also known as
exothermic is a reaction where
energy is liberated. Ex: cellular
respiration
Types of reactions:
 Endergonic reaction: also known as
endothermic is a reaction that
absorbs and uses more energy than is
released. Ex: photosynthesis
Activation Energy
 Most reactions do not occur
spontaneously. They require
activation energy (EA) which is the
energy needed to strain and break
the reactants bonds and kick start the
action.
ATP
 Adenosine triphosphate (ATP) is the
primary source of free energy in living cells.
It is made of adenine (a nitrogenous base)
+ ribose (a 5 carbon sugar) + a chain of 3
phosphate groups.
 When a cell needs energy for an
endothermic reaction it uses the
enzyme ATPase to catalyse the
hydrolysis of an ATP molecule. The
result is an ADP molecule (adenosine
diphosphate), a molecule of inorganic
phosphate, Pi, and the release of
31kJ/mol of free energy which can now
be used as activation energy for an
endothermic reaction.
 ATP recycles some of its own
produced free energy to make more
ATP.
 A single working muscle cell uses
about 600 million ATP molecules per
minute!
Homework
 Questions 1,2,3,4,5a,10 on page 68