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

AP Biology 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.

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

AP Biology The 2 nd 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

AP Biology 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

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

AP Biology 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

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

AP Biology What drives reactions?  If some reactions are “downhill”, why don’t they just happen spontaneously?  because covalent bonds are stable bonds

AP Biology 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 energy cellulose CO 2 + H 2 O + heat

AP Biology 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”

AP Biology Catalysts  So what’s a cell got to do to reduce activation energy?  get help! … chemical help… ENZYMES GG

AP Biology Energy needs of life  Organisms are endergonic systems  What do we need energy for?   synthesis (biomolecules)  reproduction  active transport  movement  temperature regulation

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

AP Biology Metabolic Strategies  Temperature must be maintained for metabolic reactions.  Ectotherms vs. endotherms  Body size vs. metabolic rate

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

AP Biology ATP Living economy  Fueling the body’s economy  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

AP Biology ATP high energy bonds  Adenosine Triphosphate  modified nucleotide  nucleotide = adenine + ribose + P i  AMP  AMP + P i  ADP  ADP + P i  ATP  adding phosphates is endergonic

AP Biology How does ATP store energy?  Each negative PO 4 more difficult to add  a lot of stored energy in each bond  most energy stored in 3rd P i  3rd P i is hardest group to keep bonded to molecule  Bonding of negative P i groups is unstable  P i groups “pop” off easily & release energy  Spring Loaded! Instability of its P bonds makes ATP an excellent energy donor

AP Biology How does ATP transfer energy? P O–O– O–O– O –O–O P O–O– O–O– O –O–O P O–O– O–O– O –O–O 7.3 energy + P O–O– O–O– O –O–O  ATP  ADP  releases energy (exergonic)  Phosphorylation (adding phosphates!)  released P i can transfer to other molecules  destabilizing the other molecules  enzyme that phosphorylates = kinase ATP

AP Biology An example of Phosphorylation…  Building polymers from monomers  need to destabilize the monomers  phosphorylate! enzyme H OH C H HOHO C

AP Biology ATP / ADP cycle A working muscle recycles over 10 million ATPs per second Can’t store ATP  too reactive  transfers P i too easily  only short term energy storage  carbs & fats are long term energy storage

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) What You Have To Do

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.

Be able to use and interpret the Coefficient Q 10 equation: t 2 = higher temperature t 1 = lower temperature k 2 = metabolic rate at higher temperature k 1 = metabolic rate at lower temperature Q 10 = the factor by which the reaction rate increases when the temperature is raised by ten degrees. What You Have To Do

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

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 Q 10 value for this data. Temperature (°C)Heartbeats per minute