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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
Protein Glycogen
Glucose
Glucose
Amino acids
ANABOLIC REACTIONS
CATABOLIC REACTIONS
Glycerol
Uses energy
Uses energy
Uses energy
Yields energy
Yields energy
Yields energy
Yields energy
Triglycerides
Protein Glycogen Triglycerides
Fatty acids Amino acids Amino acids
Fatty acids
Glycerol Glucose + + +
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) Each enzyme molecule can only be used once.
b) The shape of enzyme’s active site generally fits a specific substrate.
c) The substrate molecules react with enzymes to create new enzymes.
d) Enzymes are randomly produced. With thousands of different shapes—one is likely to work.
What molecules provide energy to bodies?
1. Adenosine triphosphate (ATP) 2. Creatine Phosphate (CP) 3. Carbohydrates (Glucose) 4. 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) Endergonic b) Exergonic c) 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