All living systems require constant input of free energy All living systems require constant input of free energy. Metabolism and Energy

The First Law of Thermodynamics Energy cannot be created or destroyed, only transformed. Living systems need to continually acquire and transform energy in order to remain alive.   “Free energy”: The energy available in a system to do work.

Flow of energy through life Life is built on chemical reactions transforming energy from one form to another organic molecules  ATP & organic molecules sun organic molecules  ATP & organic molecules solar energy  ATP & organic molecules

The 2nd Law of Thermodynamics Every time energy is transformed, the entropy (“disorder”) of the universe increases. In order to increase/ maintain their internal order, living systems must process more ordered forms of matter in to less ordered ones

Living Systems are “Open” Systems Matter and energy move in to living systems from the environment. Living systems transform matter and energy and return it to the environment

Multi-Step Metabolism To increase control, living systems produce free energy in multiple-step pathways, mediated by enzyme catalysts.

Metabolic Reactions Can form bonds between molecules dehydration synthesis synthesis anabolic reactions ENDERGONIC Can break bonds between molecules hydrolysis digestion catabolic reactions EXERGONIC building molecules= more organization= higher energy state breaking down molecules= less organization= lower energy state

Endergonic vs. exergonic reactions - energy released - digestion energy input synthesis +G -G G = change in free energy = ability to do work

Stable polymers don’t spontaneously digest into their monomers What drives reactions? If some reactions are “downhill”, why don’t they just happen spontaneously? because covalent bonds are stable bonds Stable polymers don’t spontaneously digest into their monomers “spontaneous” does not imply that the change will happen quickly. Rusting is spontaneous under the right conditions and takes a long time.

Getting the reaction started… Breaking down large molecules requires an initial input of energy activation energy large biomolecules are stable must absorb energy to break bonds Need a spark to start a fire Can cells use heat to break the bonds? energy cellulose CO2 + H2O + heat

Too much activation energy for life The amount of energy needed to destabilize the bonds of a molecule moves the reaction over an “energy hill” Not a match! That’s too much energy to expose living cells to! 2nd Law of thermodynamics Universe tends to disorder so why don’t proteins, carbohydrates & other biomolecules breakdown? at temperatures typical of the cell, molecules don’t make it over the hump of activation energy but, a cell must be metabolically active heat would speed reactions, but… would denature proteins & kill cells

Catalysts So what’s a cell got to do to reduce activation energy? get help! … chemical help… ENZYMES Call in the ENZYMES! G

Energy needs of life Organisms are endergonic systems synthesis (biomolecules) reproduction active transport movement temperature regulation Organisms are endergonic systems What do we need energy for? Which is to say… if you don’t eat, you die… because you run out of energy. The 2nd Law of Thermodynamics takes over! 2005-2006

Metabolic pathways Work of life is done by energy coupling use exergonic (catabolic) reactions to fuel endergonic (anabolic) reactions energy + + energy + +

Metabolic Strategies Temperature must be maintained for metabolic reactions. Ectotherms vs. endotherms Body size vs. metabolic rate Reproductive strategies optimized

Insufficient Free Energy Production Individual = disease or death Population = decline of a population Ecosystem = decrease in complexity Less productivity Less energy moving through system

ATP Living economy Fueling the body’s economy Uses an energy currency eat high energy organic molecules food = carbohydrates, lipids, proteins, nucleic acids break them down catabolism = digest capture released energy in a form the cell can use Uses an energy currency a way to pass energy around need a short term energy storage molecule ATP Whoa! Hot stuff!

ATP Adenosine Triphosphate modified nucleotide nucleotide = adenine + ribose + Pi  AMP AMP + Pi  ADP ADP + Pi  ATP adding phosphates is endergonic Marvel at the efficiency of biological systems! Build once = re-use over and over again. Start with a nucleotide and add phosphates to it to make this high energy molecule that drives the work of life. Let’s look at this molecule closer. Think about putting that Pi on the adenosine-ribose ==> EXERGONIC or ENDERGONIC? How efficient! Build once, use many ways high energy bonds

How does ATP store energy? I think he’s a bit unstable… don’t you? How does ATP store energy? P O– O –O P O– O –O P O– O –O P O– O –O P O– O –O ADP AMP ATP Each negative PO4 more difficult to add a lot of stored energy in each bond most energy stored in 3rd Pi 3rd Pi is hardest group to keep bonded to molecule Bonding of negative Pi groups is unstable Pi groups “pop” off easily & release energy Spring Loaded! Not a happy molecule Add 1st Pi  Kerplunk! Big negatively charged functional group Add 2nd Pi  EASY or DIFFICULT to add? DIFFICULT takes energy to add = same charges repel  Is it STABLE or UNSTABLE? UNSTABLE = 2 negatively charged functional groups not strongly bonded to each other So if it releases Pi  releases ENERGY Add 3rd Pi  MORE or LESS UNSTABLE? MORE = like an unstable currency • Hot stuff! • Doesn’t stick around • Can’t store it up • Dangerous to store = wants to give its Pi to anything Instability of its P bonds makes ATP an excellent energy donor

How does ATP transfer energy? 7.3 energy P O– O –O P O– O –O P O– O –O P O– O –O + ATP ADP ATP  ADP releases energy (exergonic) Phosphorylation (adding phosphates!) released Pi can transfer to other molecules destabilizing the other molecules enzyme that phosphorylates = kinase How does ATP transfer energy? By phosphorylating Think of the 3rd Pi as the bad boyfriend ATP tries to dump off on someone else = phosphorylating How does phosphorylating provide energy? Pi is very electronegative. Got lots of OXYGEN!! OXYGEN is very electronegative. Steals e’s from other atoms in the molecule it is bonded to. As e’s fall to electronegative atom, they release energy. Makes the other molecule “unhappy” = unstable. Starts looking for a better partner to bond to. Pi is again the bad boyfriend you want to dump. You’ve got to find someone else to give him away to. You give him away and then bond with someone new that makes you happier (monomers get together). Eventually the bad boyfriend gets dumped and goes off alone into the cytoplasm as a free agent = free Pi.

An example of Phosphorylation… Building polymers from monomers need to destabilize the monomers phosphorylate! H OH C H HO C enzyme C H OH HO O + H2O +4.2 kcal/mol + ADP C H OH “kinase” enzyme C H P Monomers  polymers Not that simple! H2O doesn’t just come off on its own You have to pull it off by phosphorylating monomers. Polymerization reactions (dehydration synthesis) involve a phosphorylation step! Where does the Pi come from? ATP It’s never that simple! + ATP -7.3 kcal/mol C H P H HO C + C H O + Pi -3.1 kcal/mol

A working muscle recycles over 10 million ATPs per second ATP / ADP cycle Can’t store ATP too reactive transfers Pi too easily only short term energy storage carbs & fats are long term energy storage A working muscle recycles over 10 million ATPs per second 2005-2006

Make ATP! That’s all I do all day. And no one even notices! What’s the point? Cells spend a lot of time making ATP! “WHY?” For chemical, mechanical, and transport work Make ATP! That’s all I do all day. And no one even notices!

2. Math Skills: Gibbs Free Energy 3.1: All living systems require constant input of free energy. 2. Math Skills: Gibbs Free Energy

What You Have To Do Be able to use and interpret the Gibbs Free Energy Equation to determine if a particular process will occur spontaneously or non-spontaneously. ΔG= change in free energy (- = exergonic, + = endergonic)  ΔH= change in enthalpy for the reaction (- = exothermic, + = endothermic) T = kelvin temperature ΔS = change in entropy (+ = entropy increase, - = entropy decrease)

Spontaneity Spontaneous reactions continue once they are initiated. Non-spontaneous reactions require continual input of energy to continue.

Using the Equation To use the equation, you’ll need to be given values. Exothermic reactions that increase entropy are always spontaneous/exergonic   Endothermic reactions that decrease entropy are always non-spontaneous/endergonic. Other reactions will be spontaneous or not depending on the temperature at which they occur.

Sample Problem Determine which of the following reactions will occur spontaneously at a temperature of 298K, justify your answer mathematically: Reaction 1: A + B → AB Δ H: +245 KJ/mol Δ S: -.02 KJ / K Reaction 2: BC → B + C Δ H: -334 KJ/mol Δ S: +.12 KJ/K

4. Math Skills: Coefficient q10 3.1: All living systems require constant input of free energy. 4. Math Skills: Coefficient q10

What You Have To Do Be able to use and interpret the Coefficient Q10 equation: t2 = higher temperature t1 = lower temperature k2= metabolic rate at higher temperature k1= metabolic rate at lower temperature Q10 = the factor by which the reaction rate increases when the temperature is raised by ten degrees.

What It Means Q10 tells us how a particular process will be affected by a 10 degree change in temperature. Most biological processes have a Q10 value between 2 and 3

Sample Problem Data taken to determine the effect of temperature on the rate of respiration in a goldfish is given in the table below. Calculate the Q10 value for this data. Temperature (°C) Heartbeats per minute 20 18 25 42