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

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 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.

The 2nd Law of Thermodynamics Every time energy is transformed, the entropy (“disorder”) of the universe increases. *Loss of order or free energy flow results in death.

How do organisms maintain order? By “Coupling Cellular Processes” Using reactions that increase entropy (disorder) to power those that decrease entropy (make orderly) energy + + energy + +

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 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 an EXERGONIC 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

How Much Energy to Get Over Hump? The amount of energy needed to destabilize the bonds of a molecule Is our temperature adequate? 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

Biological Catalysts: ENZYMES Reduces the amount of Activation Energy needed to get reaction going… 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

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

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

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 Reaction 1 answer is: + 250.96 so a positive delta G means it is NOT spontaneous Reaction 2 answer is: - 369.76 so a negative delta G means it IS spontaneous

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 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 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 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!

Energy Requirements Life requires energy to run reactions The speed at which reactions occur is one’s metabolic rate. Energy needs correlate to metabolism Factors affecting energy needs: Animal size Activity Environment Minimum metabolic rate for endotherms = BMR Minimum metabolic rate for ectotherms = SMR

Size Matters! Energy needs for endothermic animals is inversely related to body size. WHY? Surface area/Volume ratio Heat loss greater and quicker for smaller animals…must eat

Activities to Regulate Metabolism Torpor – state of decreased metabolism to save energy when in difficult conditions Hibernation Estivation

Thermoregulation Heat must be regulated to keep metabolic rate stable Adaptations that help animals thermoregulate: Insulation Circulatory adaptations Cooling by evaporative heat loss Behavioral responses Adjusting metabolic heat production Hair and feathers

Ectotherms vs. Endotherms Body temperature must be regulated for metabolic reactions

Circulatory Adaptations for Thermoregulation Vasoconstriction or Vasodilation Counter-current heat exchange

Other adaptations:

Bioenergetics Transformation of energy through an organism Figure 40.17 Bioenergetics of an animal: an overview. 33

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

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

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 10 degrees.

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