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Energy & ATP
Vocab: ATP
Objectives:
1. Describe the structure of ATP and how it stores energy.
2. Give examples of work that cells perform.
3. Summarize the ATP cycle.
Life depends on the fact that energy can be converted from one form to another.
EnergyEnergy• Energy: the capacity to rearrange matter/ “do
work”• There are two basic forms of energy:
– Kinetic energy- energy of motion; moving objects do work by transferring motion to other matter
• Examples: Motion of one car causes motion of others in a crash.
• Includes: heat (random motion of molecules) & light
– Potential energy- stored energy as a result of location or structure (energy in arrangement of atoms in a molecule)
• Includes: Chemical energy- energy available to cell to do work
Energy Transformations
• Thermodynamics- study of energy transformation that occur in a system (collection of matter)
Endergonic v. Exergonic Rxns
Release EnergyEnergy in Bonds of reactants > Bonds of products Ex.: Combustion; Respiration
Energy Required/AbsorbedEnergy in Bonds of Product > Bonds of Reactants Ex.: Photosynthesis; Biosynthesis
Reactants
Pote
ntia
l ene
rgy
of m
olec
ules
Energy required
Products
Amount ofenergy
required
•Endergonic reaction, energy is absorbed from surroundings.
• Products contain more energy in bonds than reactants.
Examples of endergonic reactions?
Reactants
Amount ofenergy
released
Pote
ntia
l ene
rgy
of m
olec
ules
Energy released
Products
•Exergonic reaction, energy is released.
•Bonds of reactants contain more energy than those in the products. Examples of exergonic reactions?
Endo or Exergonic Reaction?
1. Use of gasoline in a lawn mower2. Photosynthesis3. Synthesis of a protein in a cell4. Synthesis of glycogen in a cell5. Cell Respiration6. Hydrolysis of ATP
MetabolismSum of all reactions in an organismsMetabolic Pathway: Series of chem. Rxns that builds or breaks down complex molecules.Ex: Respiration; series of rxns that breaks down glucose and slowly releases energy stored in sugar.
Coupled Reactions
Use of energy released in exergonic to drive endergonic reactions
Coupled Reactions
ATP
Cells do NOT get energy directly from foods; Chemical energy stored in food must first be converted to energy stored in ATP.
ADENOSINE TRIPHOSPHATE
Adenosine: nitrogen-containing compound called ADENINE + 5 carbon sugar called RIBOSE
Tail: 3 phosphate groups; SOURCE OF CELLULAR ENERGY.
ATP to ADP releases Energy
ATP --> ADP + P + ENERGYMore energy Less energy
(Remember: Energy cannot be gained or lost)
Phosphate groups are negatively charged & REPEL one another – This makes ATP unstable.
More Phosphate groups = more potential energy (trying to get away fr. One another).
Energy is released when ATP --> ADP + P
ADP: Adenosine Diphosphate (2 phosphates)
ATP Cycle
ATP <--> ADP + P + ENERGY
More energy Less energy
Cellular Respiration
ATP and Cellular WorkATP --> ADP + P + Energy
Enzymes transfer the “P” to other molecules = PHOSPHOROLATION
= Phosphate forms a bond with something else (something more stable; energy released)
Energy released used to MAKE THINGS HAPPEN” = “work”
EnzymesLower activation energy for reactions to proceed.
Reactionwithoutenzyme
EA with enzyme
Ene
rgy Reactants
Reaction withenzyme
EA withoutenzyme
Netchangein energy(the same)
Products
Progress of the reaction
Figure 5.14 The effect of an enzyme is to lower EA
a.
b.c.
d.
e.
f.
Enzyme (sucrase)
Active siteSubstrate(sucrose)
Induced Fit
Products released
Substrate hydrolyzed
Catalytic cycle of an enzyme:
Why don’t macromolecules such as DNA, carbohydrates, lipids spontaneously break down into simpler less energetic molecules?
• Energy barrier must be overcome, bonds between atoms must be weakened
• Referred to as energy of activation (EA)
• How can this be accomplished?
1. add heat- problem?
2. enzyme- proteins that function as biological catalyst, lowers EA and are not consumed in reaction
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