Energy

Outline

A. What is Energy?

B. Formula ∆G = ∆H - T ∆S

C. ∆G

D. ∆H

E. T

F. ∆S

A. What is Energy?

• Energy is the ability to do work • In cells this means molecules undergo a chemical change.

Generally this change results in how a starting molecule undergoes one or more chemical rxns that results in a new molecule or product at the end. E.G. glucose enters the cell and goes through glycolysis and results in two pyruvate molecules. Glucose (6 carbon molecule) to 2 pyruvate (3 carbon molecule)

• ATP is invested to do the “work” to make the change happen

• Energy exists in different forms. E.g. Chemical, mechanical, thermal, elastic, gravitational etc.• Total energy is the formula PE = KE

• This means energy is conserved in a system

• PE is non-motion while KE is motion

• Energy is conserved!

• Law of Thermodynamics

• 1st law = energy is transferred and transformed

• Organisms are open systems which means energy can absorb (photosynthesis) energy and release metabolic waste (exhale CO2) and heat (sweat)

• 2nd Law of Thermodynamics

• Every transfer or transformation increases entropy in the universe

• This means chemical rxns cause molecules to be broken apart to create new ones at random. E.g. Cellular respiration is an example of an increase in entropy. 1 Glucose molecule (6 carbon sugar) goes through a series of chemical rxns to produce carbon dioxide and water (1 carbon, 2 oxygen and 2 hydrogen, 1 oxygen). One large molecule to several smaller ones. In chemistry we also call this balancing equations…..Hello? This is what is meant by disorder and more “clutter in the room”

• The reverse is true. E.G. small molecules are arranged into more complex molecule such as an amino group plus an acid group and an “R” coming together to form an amino acid and amino acids form bonds to produce proteins! One or more small molecules to form one large molecule. This is what describes order! Got it?

So How do We Measure Energy?????

• Formula ∆G = ∆H - T ∆Sexplained • ∆G is a measure of available energy after a rxn…basically and the SI unit

is J/mole

• J stands for joules and mole is the molar mass (you should have learned about the mole in chemistry.

• Briefly a mole is the atomic mass of a given molecule. E.G. one mole of CO2 is equal to C= 12.011 plus O=15.999 X 2 =44.009. E.G. Avogadro’s # is always 6.022 x 1023 per mole!!!!!! That is one mole of anything!!!!!!!!!! The mole stands for a unit of measurement like a dozen means 12. In the Gibbs Free Energy Equation ∆G means J/mole. It is a unit of measurement.

• ∆H is the measure of enthalpy or total energy in a system. This is PE=KE and is measured in Joules.; the SI unit is Joules. This is starting/no motion of the object (PE) and ending/motion of the object (KE)

• In biology one glucose molecule has PE in the cell. When the cell metabolizes or breaks glucose apart to pyruvate (Oxidation/reduction + lysing water all with the help from enzymes) energy is transferred and transformed – we call this KE. Most is transferred to heat. Oh just as a side note you produce heat to stay warm and maintain homeostasis.

• The sum of the internal energy of the system plus the product of the pressure of the gas in the system and its volume. This is products minus the reactants….exergonic vs. endergonic rxns.

Endergonic (Endothermic) vs. Exergonic (Exothermic) RXNS

ENDO-∆H is positive, not spontaneous, and absorbs heat

Exo-∆H is negative, spontaneous and releases heat

• T = temperature in measured in Kelvin (K)

• Tabulated standard-state thermodynamic data are generally for a temperature of 25C (298 K)

• ∆S or entropy• SI unit is J/K; J is joules and K is temperature in Kelvin!

• Measure of the Disorder/Order of molecules in cells

• Large molecule like Glucose and Amino Acids represent order and in an exothermic rxn these molecules are broken down to smaller molecules that take up more space and create disorder

• Small molecules like Carbon dioxide and Water represent or amino group and an acid group represent disorder because they CAN come form chemical bonds to create larger molecules like glucose and amino acids respectively

After everything cancels out you are left with ∆G which is measured in j/mole or kcal/mole

• SPONTANEOUS: G is negative (G< 0, Keq > 1)

• NON-SPONTANEOUS: Gis positive (G > 0, Keq < 1)

• EQUILIBRIUM: G = 0 (Keq = 1)

• If you are still lost and confused do your homework and visit the Bozeman Gibbs energy website and click on the Gibbs Energy button on my website under AP Bio websites page!!!!!!!!!!!!!