Energy and Physiology

• 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

Energy and NutrientsOrganisms 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

Chemical Reactions Make Life Possible!

Autotrophs Heterotrophs and Autotrophs

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

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)

Chemical Reactions Proceed as Follows:

Reactants ProductsEnergy must be added to “activate” the reaction and break the bonds between atoms

Activation Energy

Metabolism and Energy Transfer

Types of ReactionsEndothermic

Stores energy in bonds

Ex. is photosynthesis

Types of ReactionsExothermic

Energy is released by breaking bonds

Ex. is cellular respiration

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!!!

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

Protein molecules that act as catalysts

Specific to a Substance or Reaction

Speeds up Biological Reactions to 10,000,000,000 times faster

Enzymes

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

E + S ES E + PCatalase

Breaks H2O2 into H2O and O2

Hydrogen Peroxide is Toxic to Cells

Catalase + H2O2 Complex Catalase + H2O + O2

Enzymatic Reactions

Induced Fit

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

Factors Effecting Enzyme Action

Metabolism: All the chemical activities in a cell or organism

Chemical Reactions in Organisms

Synthesis “building-up” reactions

Anabolism; biosynthesis

photosynthesis

dehydration synthesis

Decomposition

“breaking down” reactions

Catabolism

cellular respiration

digestion

hydrolysis

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

ATPATP 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