Metabolism: Energy
and Enzymes
By: Holly Davis and Diana Brizan
Energy:
the ability to do work or
bring about change. Develop, grow and
reproduce.
 There are many different types of energy
 Kinetic is energy of motion (a ball
rolling)
 Mechanical is also a ball rolling or
muscle contracting
 Solar energy is energy from the sun
 Potential is stored energy (food we eat)
 Chemical energy (organic molecules)
Laws of Thermodynamics
1. The law of conservation of energy.
Energy cannot be created or destroyed,
but it can be changed from one form to
another.
2. Second Law
Energy cannot be changed from one
form to another without a loss of usable
energy.
 Entropy: measures relative amount of disorder or
randomness.
 Every process in cells increases total entropy,
making less energy available to do work in the
future.
 Eventually all usable forms of energy become heat.
Heat cannot be converted to any other form of
energy.
Metabolic Reaction
 Metabolism - sum of all chemical reactions
that occur in a cell
Product A and B
A + B  AB
Join to form the
reactant AB
 Reactants – substances that participate in
reaction
 Products – substances that are formed as a
result of reaction
 A spontaneous reaction increases total entropy.
 Free energy “G” – amount of energy still free after
a chemical reaction has taken place.
 Exergonic reactions – product has less free
energy then reactants
 Endergonic reactions – product has more free
energy then reaction, they can only occur if there
is an input of energy.
Endergonic reaction
ATP (adenosine triphosphate)
 Carrier of energy
 Common energy currency,
can be used in many
different types of reactions
 ATP is constantly being
made from ADP (adenosine
diphosphate) and
Phosphate, little energy is
wasted
Coupled Reaction :
when the energy
released from an
exergonic reaction is
used to drive an
endergonic reaction
blue – ribose (5 carbon sugar)
Green - adenine (a nitrogenous base)
Yellow – phosphate groups
Metabolic Pathways &
Enzymes
 Reactions in cells occur
usually because they are
part of a metabolic
pathway, series of linked
reactions.
 Enzyme is a protein molecule that functions
as an organic catalyst to speed chemical
reaction
 Reactants in enzymatic reaction are called
substrates for that enzyme
Enzyme Substrate Complex
 One part of the enzyme is called the active
site, which complexes with the substrate.
 Fit together like “key and lock”. Induced Fit
Model means that it undergoes slight
change for optimum fit.
 Every reaction requires
its specific enzyme
Factors Affecting Enzymatic Speed
Substrate Concentration: Enzyme
activity increases as
Enzyme Concentration: If
concentration increases. When all
there are too many
active sites filled, max rate,
enzymes present they
cannot increase any more
can get in the way. Only
Temperature and pH:
certain enzymes work for
Higher temperature increases
certain substrates.
enzyme activity. KMT, higher
Enzyme Inhibition: when
collision between enzyme and
an active enzyme is
substrate. Too hot becomes
prevented from
denatured.
combining with its
At optimal pH the reaction is
substrate, eg. poisons.
highest. Extreme conditions of pH
also denatures the enzyme
Oxidation-Reduction
 Oxidation – the loss of electrons
 Reduction – gain of electrons
 Example: Na + Cl  NaCl
sodium has been oxidized, chlorine has been reduced
 When oxidation and reduction go hand in hand it is
called a redox reaction
This is an example of a
spontaneous redox reaction. When
zinc metal is placed in a solution of
copper sulfate, the copper is
reduced and appears as a black
coating on the zinc.
Photosynthesis and cellular respiration permit a
Flow of Energy
all living things
Photosynthesis:
energy + carbon dioxcide + water
 glucose + oxygen
Chloroplasts capture solar energy
and convert it into ATP
Cellular Respiration:
Glucose + oxygen  carbon
dioxcide + water + energy
When ATP is used up as an
energy source, all useable
energy is converted into heat
from the sun through
Bibliography
 Inquiry Into Life ~ Slyvia S. Mader
 http://www.people.vcu.edu/~rgowdy/mod/020/bow.gif
 http://resources.yesicanscience.ca/energy_flow/images/kinetic_energy1.png
 http://regentsprep.org/Regents/biology/units/homeostasis/lo
ckkey.gif
 http://www.brooklyn.cuny.edu/bc/ahp/LAD/C7/graphics/C7_a
tp_1.GIF
 http://www.polk.edu/instruct/Mash/bane/BSC1005/Energy.ht
ml
 http://kentsimmons.uwinnipeg.ca/cm1504/respiration.htm
 http://genchem.chem.wisc.edu/demonstrations/Images/04ch
emrxn/sponoxred.jpg