Organisms obtain energy through chemical reactions. Autotrophs like plants produce their own food through photosynthesis, an endothermic reaction that stores energy. Heterotrophs obtain energy by consuming other organisms. All organisms must obtain energy from outside sources according to the first law of thermodynamics. Chemical reactions are catalyzed by enzymes to make them fast enough to support life. Energy is required for synthesis reactions and released by decomposition reactions like cellular respiration. ATP is used to store and transport energy in cells.

1. Energy and Physiology

2. •Energy is the capacity to do work or cause change
•Organisms store energy in organic molecules as chemical energy
•Free energy is the portion of energy released during chemical reactions
that is available to do work
Energy and Nutrients

3. Energy and Nutrients
Organisms obtain their energy through Autotrophy or Heterotrophy
Autotrophs are organisms capable of producing their own food
Heterotrophs are organisms that must obtain food from an outside source
by consuming another organism

4. Chemical Reactions Make Life Possible!
Autotrophs Heterotrophs
and Autotrophs

5. The Law of Conservation of Energy (1st Law of Thermodynamics)
•Energy cannot be created or destroyed, but it can change form
•The total energy of the universe is constant
•Organisms cannot create their own energy but must obtain it from an
outside source

6. The Second Law of Thermodynamics
•There is a natural tendency towards disorder “entropy”
•Energy is required to resist entropy
•An organism must be well organized to remain alive and grow
(Organization requires energy)

7. Chemical Reactions Proceed as Follows:
Reactants Products
Energy must be added to “activate” the reaction and
break the bonds between atoms
Activation Energy
Metabolism and Energy Transfer

8. Types of Reactions
Endothermic
Stores energy in bonds
Ex. is photosynthesis

9. Types of Reactions
Exothermic
Energy is released by breaking
bonds
Ex. is cellular respiration

10. Energy Curve of an Uncatalyzed Exothermic
Reaction
Energy of
Reactants
Energy of
Products
Activation Energy
In cases like this (High
AE), reactions would occur
too slowly to support life!!!

11. Catalysts speed up the rate of a reaction by lowering the
activation energy needed to get the reaction going
Catalysts are not changed or used up during a reaction!
Catalysts

12. Protein molecules that act
as catalysts
Specific to a Substance or
Reaction
Speeds up Biological
Reactions to
10,000,000,000 times
faster
Enzymes

13. Bind to Specific Reactants to Form a complex
Reactants enzymes interact with are called Substrates
Substrate binds to the enzyme at a location called the Active Site
How Enzymes Work

15. E + S ES E + P
Catalase
Breaks H2O2 into H2O and O2
Hydrogen Peroxide is Toxic to Cells
Catalase + H2O2 Complex Catalase + H2O + O2
Enzymatic Reactions

16. Induced Fit

17. Enzymes are named by taking either the name of the
substrate or the action performed and adding the ending “ase”
DNA Polymerase
Lactase
Ligase
Naming Enzymes

18. Factors Effecting
Enzyme Action

19. Metabolism: All the chemical activities in a cell or
organism
Chemical Reactions in Organisms

20. Synthesis
“building-up” reactions
Anabolism; biosynthesis
photosynthesis
dehydration synthesis

21. Decomposition
“breaking down” reactions
Catabolism
cellular respiration
digestion
hydrolysis

22. Decomposition reactions release free energy
Oxidation is the removal of electrons from a molecule
Bonds are broken and rearranged
Some energy of the original molecule is released as heat and free energy
Free energy is finally captured in ATP (adenosine triphosphate)
Energy Exchange in Cells

23. ATP
ATP is the cellular energy currency
Can store/release small amounts of energy
The bond between the 2nd and 3rd phosphate is made or
broken to exchange energy