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AP Biology All living systems require constant input of free energy. Metabolism and Energy
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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.
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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
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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
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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
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AP Biology Multi-Step Metabolism To increase control, living systems produce free energy in multiple-step pathways, mediated by enzyme catalysts.
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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 breaking down molecules= less organization= lower energy state building molecules= more organization= higher energy state
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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
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AP Biology 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
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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 Can cells use heat to break the bonds?
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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” Not a match! That’s too much energy to expose living cells to!
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AP Biology Catalysts So what’s a cell got to do to reduce activation energy? get help! … chemical help… ENZYMES GG Call in the ENZYMES!
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AP Biology 2005-2006 Energy needs of life Organisms are endergonic systems What do we need energy for? synthesis (biomolecules) reproduction active transport movement temperature regulation
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AP Biology Metabolic pathways Work of life is done by energy coupling use exergonic (catabolic) reactions to fuel endergonic (anabolic) reactions ++ energy + +
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AP Biology Metabolic Strategies Temperature must be maintained for metabolic reactions. Ectotherms vs. endotherms Body size vs. metabolic rate Reproductive strategies optimized
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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
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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 Whoa! Hot stuff!
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AP Biology ATP high energy bonds How efficient! Build once, use many ways Adenosine Triphosphate modified nucleotide nucleotide = adenine + ribose + P i AMP AMP + P i ADP ADP + P i ATP adding phosphates is endergonic
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AP Biology How does ATP store 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 P O–O– O–O– O –O–O P O–O– O–O– O –O–O P O–O– O–O– O –O–O P O–O– O–O– O –O–O P O–O– O–O– O –O–O 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 I think he’s a bit unstable… don’t you? AMP ADPATP
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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 ADPATP
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AP Biology It’s never that simple! An example of Phosphorylation… Building polymers from monomers need to destabilize the monomers phosphorylate! C H OH H HOHO C C H O H C + H2OH2O + +4.2 kcal/mol C H OH C H P + ATP + ADP H HOHO C + C H O H CC H P + PiPi “kinase” enzyme -7.3 kcal/mol -3.1 kcal/mol enzyme H OH C H HOHO C
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AP Biology 2005-2006 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
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AP Biology 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!
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AP Biology 2. M ATH S KILLS : G IBBS F REE E NERGY 3.1: All living systems require constant input of free energy.
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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
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Spontaneity Spontaneous reactions continue once they are initiated. Non-spontaneous reactions require continual input of energy to continue.
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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.
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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
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4. M ATH S KILLS : C OEFFICIENT Q 10 3.1: All living systems require constant input of free energy.
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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
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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
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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 2018 2542
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