Transcript Cellular Energetics - Mount Mansfield Union High School

How do cells acquire and use Energy?
Why is energy essential to life?
 cell division
 movement of flagella or cilia
 the production and storage of
proteins
 muscle contractions during
exercise
 your heart pumping
 your brain controlling your
entire body
What is energy?
 The capacity to do work
 ie. change or move something
 chemical energy= changes structure
 mechanical energy= move objects
 light energy= boosts electrons to an outer shell
 thermal energy (heat)= increases the motion of molecules
Potential vs. Kinetic energy
 A.K.A.-- stored vs. expended energy
 glycogen is potential energy that when broken down and
metabolized is kinetic energy that is used by muscles
 Chemical bonds store energy that can be released when
the bond is broken.
 Just as some springs are tighter than others, some
chemical bonds store more energy than others.
The Laws of Thermodynamics
 # 1: The law of Energy Conservation “Energy is neither created nor
destroyed”
 Examples:
 Electrical energy is converted to
mechanical energy when we plug
in a clock or turn on a blender
 Green plants convert solar energy
into chemical energy that is stored
as starch or cellulose and used by
the plant
#2: With each energy transfer,
some energy is lost
 Every time energy changes or moves, some
of it, or all of it, becomes less useful
 Examples:
 Remember Food Chains? As you move
further and further up the food chain, there
is less available energy.

When you exercise, some of the food energy
gets converted into muscle work, but most of it
gets converted to thermal energy. That's why
you get all hot and sweaty..
 Cars convert chemical energy (gasoline) into
mechanical energy in order to turn the
wheels.

Heat is generated and must be removed by a
radiator and only about 5% of the chemical
energy is converted into the mechanical energy
which moves the car.
ENTROPY
 a natural tendency towards disorder. It requires
energy to fight disorder. Think of your bedroom, for
example!
 Cells spend energy to fight this tendency so they use
ATP
Adenosine triphosphate
 a.k.a ATP
 is the energy molecule that transports chemical energy
within cells!
 It is made up of an adenine and a ribose molecule
(a.k.a. adenosine)+ three phosphate groups
Things to know about ATP:
 The phosphate groups are charged
molecules

molecules with the same charge do not like being too
close to each other.
 Bonding phosphate groups to the
adenosine requires CONSIDERABLE
energy.

So much energy is required to force the third charged
phosphate close to the other two, that when the bond is
broken, a great amount of energy is released.
 When the chemical bonds between phosphate
groups in ATP are broken, energy is released and
ADP is formed.
 ADP can reform ATP by bonding with another
phosphate group.
animation
Another animation
A few more tid-bits about ATP:
 No storage is necessary–
 This cycle or formation/breakdown is important so a cell
doesn’t have to store all of the ATP it needs. As long as
phosphate molecules are available, the cell has an unlimited
supply of energy.
 Use it or lose it!
 ATP is broken down and the released energy must be captured
and used efficiently—otherwise it will be wasted.
 Think of a rechargeable battery—
 it’s of little use sitting on a table, but if you snap it into the
holder on the radio, the radio then has access to the stored
energy and can use it. Then, when the energy has been used
up, the batteries can be taken out, recharged, and replaced
into the radio.
Different types of reactions
 The energy-related reactions within cells generally
involve the synthesis or the breakdown of complex
organic molecules. Here’s the difference:
 Anabolic reactions



are those that synthesize compounds
Energy is required for these reactions.
Also called endergonic
•Catabolic reactions
•Reactions that break down
molecules
•Energy is released when molecules
are broken down.
•Also called exergonic
Activation Energy
 Energy required to cause even spontaneous reactions
to begin
Is this an example of an
Endergonic or Exergonic
Reaction?
What are enzymes?
 catalysts
 most are proteins
 speed up chemical reactions
Enzymes bind temporarily to one or more of the reactants
of the reaction they catalyze.
In doing so, they lower the amount of activation energy
needed and thus speed up the reaction
Overview
Real World Examples:
 Catalase- catalyzes the decomposition of
hydrogen peroxide into water and oxygen.
 2H2O2 -> 2H2O + O2
 One molecule of catalase can break 40 million
molecules of hydrogen peroxide each second.
 Carbonic anhydrase- is found in red blood
cells where it catalyzes the reaction
 CO2 + H2O <-> H2CO3
 It enables red blood cells to transport carbon
dioxide from the tissues to the lungs.
The Lock & Key Analogy
 In order to do its work, an enzyme must unite — even
if ever so briefly — with at least one of the reactants.
Successful binding of enzyme and substrate requires that
the two molecules be able to approach each other closely
over a fairly broad surface.
Vocab to Know:
 Substrate(s) The reactants which bind to enzymes and are
subsequently converted to a product or products
 Active Site the area on the enzyme that binds the substrate(s)
 The active site and the substrate(s) have complementary
shape – like pieces in a jig-saw puzzle.
Factors that Effect Enzyme Activity
 Heat
 first it boosts enzyme activity by
increasing molecular motion.
 Above a critical temperature, the
rate of reaction rapidly decreases
because enzymes change shape
and get denatured.
 Cold slows reaction time down
pH
 a rise or fall in H+ conc. can change the charge of
amino acid and affect the structure of the active site.
Concentration
 Increased concentration of enzyme does not increase
the rate of reaction once a critical conc. is reached.
 This is because enzymes are recycled.
Competitive inhibitors an inhibitor has a similar structure as the substrate and
clogs the active site so enzymes cannot work (ex. sulfa
drugs)
Heavy Metals
 can bind nonspecifically to an enzyme and alter their
shape so that they cannot function properly
 ex. lead, mercury, & arsenic
Bigger Picture
 Metabolic Pathways A set of enzymatic reactions involved in either building
or dismantling complex molecules
 Feedback Inhibition when a key enzyme in a metabolic pathway is
temporarily inactivated when the conc. of the end
product of the pathway becomes elevated.
One final animation