ENERGY& METABOLISM

ENERGY Energy is the capacity to do work Energy exists in multiple forms Light Heat Electricity Chemical bond energy Etc. These various types of energy can be places into two groups Kinetic energy Potential energy

KINETIC ENERGY “Energy of motion” Anything that moves possesses kine e.g., Heat, light, balls on a pool table, flowing water, flowing electrons, etc.

POTENTIAL ENERGY “Energy of location or structure” “Stored energy” Resting objects may still possess energy e.g., A rock at the top of a hill, chemical bond energy

Potential Energy Diagram: shows changes in potential energy during a chemical reaction. Activation Energy EA Transition state Exergonic

THERMODYNAMICS “Energy cannot be created or destroyed” First Law of Thermodynamics (The Law of Conservation of Energy) “Energy cannot be created or destroyed” “The total amount of energy in the universe is constant”

THERMODYNAMICS Energy cannot be created or destroyed However, it can be converted from one form to another What energy transformations are taking place here?

THERMODYNAMICS If energy cannot be created or destroyed, why do living things need continual inputs of energy?

THERMODYNAMICS The Second Law of Thermodynamics “Every energy transformation makes the universe more disordered” Entropy is a measure of this disorder or randomness “Every energy transformation increases the entropy of the universe” “When energy is converted from one form to another, some fraction of the potentially usable energy is lost” Not destroyed, but converted to entropy

THERMODYNAMICS I weighed eight pounds and change at birth I weigh slightly more than eight pounds now I have increased in order and complexity Isn’t this counter to the Second Law?

THERMODYNAMICS The Second Law of Thermodynamics Note that we have talked about the universe as a whole, not each individual part of the universe The universe is a “closed system” No energy enters or leaves In a closed system, entropy increases

THERMODYNAMICS The Second Law of Thermodynamics You, as an individual, can increase in order You do so at the expense of your environment Overall, the net change in you and in your environment is an increase in disorder You + environment = a closed system

THERMODYNAMICS Certain events occur spontaneously, while others do not Spontaneous processes occur (once initiated) without outside help e.g., Water flows downhill, not uphill How can we explain this?

THERMODYNAMICS The free energy released in spontaneous processes can be harnessed to do work

THERMODYNAMICS What energy transformations are occurring here? What is the spontaneous process? Is work being done?

CHEMICAL REACTIONS Some chemical reactions release free energy Spontaneous reactions Exergonic reaction / Exothermic Some chemical reactions require free energy in order to proceed Non-spontaneous reactions Endergonic reaction /Endothermic The energy released in exergonic reactions can be used to drive endergonic reactions

NEED FOR ENERGY The environment within a cell is highly organized and separate from the external environment Maintaining this ordered environment costs energy Many processes within a cell require energy The requirement for energy is a unifying feature of life Many organisms extract energy from food via aerobic cellular respiration

Metabolism: the sum of all the anabolic(energy storing) and all the catabolic activities(energy releasing) in the cell Identify each of the following activities as either anabolic or catabolic: (a) protein synthesis (b) digestion (c) DNA synthesis (d) photosynthesis (e) cellular respiration

CELLULAR RESPIRATION Cellular Respiration is the controlled breakdown of glucose -catabolic CR involves a series of chemical reactions that release free energy Exergonic reactions/Exothermic spontaneous This free energy is used for cellular work

Redox Reactions: Cellular respiration is also know as the “Oxidation of Glucose” Oxidation is a chemical reaction in which an atom loses one or more electrons. Lost electrons must have somewhere to go Reduction is a chemical reaction in which an atom gains one or more electrons. A redox reaction - oxidation coupled with reduction!

Free energy in the body =ATP ATP couples of energy-releasing (exergonic) reactions to energy-requiring (endergonic) reactions

ATP CYCLE ATP and ADP are readily interconverted ATP  ADP releases energy * ADP  ATP requires energy **

The hydrolysis of the terminal phosphate of ATP in a living cell yields and energy value ~54 kJ/mol

ATP CYCLE - phosphorylation Energy-releasing reactions store energy as ATP ADP  ATP Energy-requiring reactions receive energy from ATP ATP  ADP

IS THERE ENOUGH ENERGY TO RUN ALL METABOLIC PROCESSES IN A CELL?? WHAT HAPPENS TO THE ENTROPY PRODUCED IN ALL THE CHEMICAL CONVERSIONS IN A CELL?? IN A BODY??

The laws of thermodynamics define which reactions are spontaneous and which are not… Some reactions are spontaneous but occur at nearly imperceptibly slow rates Too slow to sustain life Enzymes can increase the rate of chemical reactions by more than 100 000 x