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Cellular Energy:
ATP & Enzymes
What is it? Where do organism’s
get it? How do they use it?
Where does
Energy come
from?
• Ultimately, from the
sun.
• It is transferred
between organisms in
the earth’s
lithosphere, but is
slowly lost with every
transfer
Energy
• The capacity to perform work; to
rearrange matter
• 2 forms:
– Potential Energy (PE): stored energy, due to
position or structure
– Kinetic Energy (KE): Energy of motion
• Heat is KE associated with the movement of
molecules/atoms
Energy is transferred not
created
• Total amount of Energy in Universe is
constant (1st Law)
– Nothing created or destroyed, only
transformed
• One result of ALL energy transfers is
the production of heat (2nd Law)
– Heat = disordered, unharnessed KE. This KE
is LOST; cannot be used to perform work
Heat loss during rxns
Chemical Reactions
• Reactants (Substrates): The starting
materials that are consumed during a
chemical reaction.
• Products: The ending materials of a
chemical reaction.
• Endergonic (energy input): Store Energy –
products have higher energy than
reactants.
• Exergonic (energy output): Release
Energy – products have lower energy.
Endergonic
• Products have more
energy than
reactants
• Photosynthesis:
– Reactants = CO2 &
H2O + light energy
– Products = sugar
molecules
Exergonic
• Reactants have more
energy than products
• Bonfire
– Reactants: Cellulose
(glucose), O2
– Products: light, heat,
CO2, H2O
• Cellular respiration
“burns” glucose to
harness energy for
work
Anabolic and Catabolic Reactions
ANABOLIC REACTIONS
Triglycerides
Glycogen
Uses
energy
Uses
energy
Glucose
+
Glucose
Glycerol
Protein
Uses
energy
+
Fatty acids
Amino acids + Amino acids
CATABOLIC REACTIONS
Glycogen
Glucose
Yields
energy
Triglycerides
Glycerol
Yields
energy
Protein
Fatty acids
Yields
energy
Amino acids
Yields
energy
Cellular metabolism
• The sum of all cellular endergonic and
exergonic reactions.
• The ATP molecule delivers and transfers
energy to parts of a cell that are
conducting these reactions.
ATP
• Sugar, base, and…
• 3 phosphates
groups
• Covalent bonds +
negatively charged
phosphates groups
= high PE!
Energy Transfer
• Some freed energy is lost as heat
• The rest is transferred via the phosphate
group when it binds to another molecule
(phosphorylation)
ATP fuels ALL cellular work
ATP is continually regenerated
Enzymes are also required to
drive reactions
Exergonic Reaction without
Enzyme
Enzymes lower Activation Energy
• Some energy (EA) must be applied to begin a rxn
– Sometimes the energy barrier is prohibitively large
– Enzymes reduce that barrier, allowing rxn to
proceed with LESS energy input
Enzyme are not consumed,
they are recycled
1. Available enzyme
w/ active site
2. Substrate binds
3. Conversion to
products
4. Products
released
Enzymes possess:
• Ideal temperature regimes
• Ideal pH ranges
• Cofactors (inorganic molecules & ions)
and coenzymes (organic molecules)
Competition & Inhibition
• Some molecules may
“mimic” enzymes
(competitive inhibition)
– Either shutdown OR
accelerate reaction
• Others change enzyme
conformation
(noncompetitive
inhibition)
– Always shuts down
reaction
Concept Check
•
Enzymes catalyze reactions in a cell.
There are hundreds of different
enzymes in a cell—each with a unique
three-dimensional shape. Why do cells
have so many different enzymes?
a)
b)
c)
d)
Each enzyme molecule can only be
used once.
The shape of enzyme’s active site
generally fits a specific substrate.
The substrate molecules react with
enzymes to create new enzymes.
Enzymes are randomly produced.
With thousands of different shapes—
one is likely to work.
What molecules provide
energy to bodies?
1.
2.
3.
4.
Adenosine triphosphate (ATP)
Creatine Phosphate (CP)
Carbohydrates (Glucose)
Fats
What molecules provide
energy to organisms?
• Adenosine triphosphate (ATP) – THE
energy carrying molecule in the body
• Muscles store only enough ATP for 1 – 3
seconds of activity
– ATP is generated continuously
• Usually via carbohydrate catabolism with or
without O2
ATP structure
Substrates for producing ATP
• After depleting stored ATP, cells turn to
other sources of stored energy to
regenerate ATP:
– Creatine phosphate (CP)
– Carbohydrates (Glucose)
– Triglycerides
CP transfers P to make ATP
Glucose metabolism
In cytoplasm
In mitochondria
Fats as fuel
• Stored triglycerides (storage form of fats) are
metabolized to generate ATP for:
– Low intensity exercise
– Exercise of long duration
• Ex: 10 hr. hike + moderate climb
• Abundant energy source, even in lean
people
• Provides 2x more energy per gram as
carbohydrate
Distribution
– ATP/CP
– Carbohydrates
– Fats
– Protein
Energy use over time:
Increasing intensity
Interpreting Data
•
This graph illustrates how
an enzyme catalyzes
reactions in biological
systems. From an energy
standpoint is this reaction
an endergonic or exergonic
reaction?
a)
b)
c)
Endergonic
Exergonic
There is not enough
information in this graph
to decide the type of
reaction.
Interpreting Data
•Which of the following
represents the energy
of activation after
modification by an
enzyme?
–
–
–
A.
B.
C.
Answer
•Which of the following
represents the energy of
activation after
modification by an
enzyme?
–
A.
Energy