What Is Metabolism???  Thousands of chemical reactions that occur in the cell  Concerned with the managing of materials and energy resources of the cell  2 main metabolic pathways  Catabolic Pathways  Anabolic Pathways

Catabolic Pathways  Release energy by breaking down complex molecules to simpler compounds  Example in living organisms???

Anabolic Pathways  Energy absorbing processes that build complex molecules from simple molecules  Examples????

Energy  The ability to do work  The ability to move matter against opposing forces  Relationship between kinetic energy, potential energy, chemical energy???

 Kinetic Energy: Energy of motion  Potential Energy: Stored energy  Chemical Energy: Energy stored in the bonds of molecules

Thermodynamics  The study of the energy transformations that occur in a collection of matter  What is an closed system???  What is an open system???

1 st Law of Thermodynamics  Energy cannot be created or destroyed, it can only be transferred or transformed  Principle of conservation of energy  What prevents organisms from behaving like closed systems and recycling their energy???

2 nd Law of Thermodynamics  Every energy transfer or transformation increases the entropy of the universe  Explain entropy.  What is the role of heat in energy transformation???

1 st and 2 nd Laws Combined  Explain the following Quantity of energy in the universe is constant, but quality of energy is not constant

Entropy vs. Life  How can the 2 nd law of thermodynamics be reconciled with the fact that many life processes decrease entropy???  Living organisms are open systems  Energy enters ecosystems as light and leaves as heat – increasing the entropy of their environment

Spontaneous Process  Change that can occur without help (or an input of energy)  Can be used to perform work  Increases the entropy of the universe  Unstable systems are those which can change by a spontaneous process and become more stable

Free Energy  Is free energy free?????? What????  Free energy is spent with a cost to the universe  Definition: the portion of a system’s energy that can perform work when temperature is uniform throughout the system

Free Energy Equation  G = H – TS  G = free energy  H = total energy in system  S = entropy  T = temperature

Spontaneity and Free Energy  For a process to occur spontaneously, the system must give up energy (decrease in H) or increase entropy (increase in S), or both  G must have a negative value or nature runs “downhill” 

Relationship between free energy and equilibrium  Equilibrium means that a process has reached maximum stability  As processes proceed toward equilibrium, the amount of free energy decreases  For chemical reactions in equilibrium G = 0

Exergonic and Endergonic Reactions  Exergonic Reaction  Reactions that release energy  G is negative  Work can be done  Endergonic Reaction  absorbs free energy from its environment  G is positive

Examples  Exergonic reaction C 6 H 12 O 6 + 6O 2  6CO 2 + 6O 2 G = -686 kcal/mol  Endergonic reaction 6CO 2 + 6O 2  C 6 H 12 O 6 + 6O 2 G = +686 kcal/mol

Metabolic Disequilibrium  Living organisms are open systems  Reactions in a closed system will reach equilibrium, where no work can be done  Cells that reach metabolic equilibrium are dead  What keeps cells from reaching metabolic equilibrium???

What is Energy Coupling?  The use of exergonic processes to drive endergonic ones  This is possible because of ATP  Give an example of energy coupling.

What are the 3 main types of work performed by a cell???  Mechanical work  Transport work  Chemical work

Structure of ATP  Adenosine triphosphate Adenine – nitrogenous base  Where else is this found?  Ribose – what type of molecule is this?  3 phosphate groups

ATP as an Energy Storing Compound  Phosphate-phosphate bonds can be broken by hydrolysis  Inorganic phosphate is released when the bond is broken  ATP + H 2 O  ADP + P i  G = -7.3 kcal/mol (under standard conditions)  What is the free energy yield in a cell? Why???

How does ATP transfer energy?  Phosphate bonds are relatively weak  Their instability allows energy to be released when hydrolysis occurs  ADP is more stable than ATP  Which molecule has more free energy?

Why are the phoshate bonds so unstable???  ATP contains three negatively charged phosphate groups  How do like charges respond to each other???

How does ATP perform work???  Phosphate group is released from ATP  Another molecule receives the inorganic phosphate – it becomes phosphorylated  Phosphorylated molecules are the key to energy coupling

Example 1.Glutamic acid + NH3  glutamine G = +3.4 kcal/mol nonspontaneous 2. Glutamic acid + ATP  glutamic acid-P + ADP Glutamic acid-P + NH 3  glutamine + P i  What is the net change in free energy in the second rxn.? Explain.

The ATP Cycle  Describe the ATP cycle.  Why is it important that ATP be regenerated efficiently in working cells (be specific)?  How is ATP regenerated??? What is the change in free energy? Is this process spontaneous?

Enzymes  What is a catalyst? A chemical that changes the rate of a reaction without being comsumed by the reaction An enzyme is a catalytic protein

Activation Energy  The initial investment of energy for starting a reaction  Molecules must absorb enough energy to become unstable  Exergonic reactions have a net release of energy, in spite of E A

 Free energy must be added to start a reaction  This causes the original bonds to become unstable – What is this state called???  The difference between the free energy in the reactants and the free energy in the products is G for the overall reaction

Enzymes and E A  Most molecules do not spontaneously react at the normal temperature of the cell  Why is heat a poor choice for moving metabolic pathways in living cells???  What is the alternative to heat???

How do enzymes work???  Enzymes lower activation energy  Enzymes speed up chemical reaction  Enzymes allow reactions to occur in cells at normal cell temperatures  Enzymes speed up metabolism

Essay Quiz  5 minute reading period Used to organize thoughts and outline essay  22 minutes to write the essay  Essay must be written in paragraph form

Essay  Explain why enzymes are substrate specific and describe the role of the active site in an enzymes ability to lower E A. Give specific example of how amino acid side chains can affect a substrate.  How do a cell’s physical and chemical environment affect enzyme activity? Discuss the role of temperature, pH, cofactors, and enzyme inhibitors in enzyme activity. Be specific and give example where possible.