AP Biology Unit 2: Cellular Metabolism -Connection with Big Idea 2: All living organisms require energy

AP Biology Metabolism  An organism’s chemical reactions  Forming bonds between molecules  Dehydration synthesis  Anabolic reactions  Breaking bonds  Hydrolysis  Catabolic reactions

AP Biology

Forms of Energy  Kinetic  Thermal energy and heat  Potential

AP Biology Organisms are energy transformers  How?

AP Biology The Laws of Energy Transformation -Thermodynamics 1. Energy can be transferred and transformed but cannot be destroyed or created 2. Every energy transfer or transformation increases the entropy of the universe

AP Biology Free-energy Change  A Measurement of the amount of "useful" energy  At the cellular level, the major biological source of energy is from the rearranging of atoms to from higher energy compounds to lower energy compounds.

AP Biology G= H- T S  G = Free Energy  H = Enthalpy (energy stored in a substance)  T = Temperature (Kelvin)  S = Entropy

AP Biology Importance of Free Energy  Tells us what might happen  Measure of system’s instability  Tendency to move to more stable state  Unstable systems have higher G, stable have lower G  What about equilibrium?

AP Biology Free Energy and Metabolism 2 main reactions 1. Exergonic- net release of free energy, G is negative 2. Endergonic- absorbs energy (energy stored in molecules) -Nonspontaneous -G is positive

AP Biology

So how do the two interact?  Example: metabolism in plants  1. Photosynthesis  Stores energy- what is this process?  2. Cellular respiration  Releases energy- what is this process?

AP Biology

Equilibrium and Metabolism  Isolated system- reach equilibrium  If reach equilibrium, G is minimal and can do no work  If this is a cell- dead!

AP Biology ATP Making energy! The point is to make ATP!

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

AP Biology Where do we get the energy from?  Work of life is done by energy coupling  use exergonic (catabolic) reactions to fuel endergonic (anabolic) reactions ++ energy + + digestion synthesis

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

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

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  spring-loaded  P i groups “pop” off easily & release energy Instability of its P bonds makes ATP an excellent energy donor I think he’s a bit unstable… don’t you? AMP ADPATP

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  ∆G = -7.3 kcal/mole  Fuel other reactions  Phosphorylation  released P i can transfer to other molecules  destabilizing the other molecules  enzyme that phosphorylates = “kinase” ADPATP

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 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 synthesis

AP Biology Another example of Phosphorylation…  The first steps of cellular respiration  beginning the breakdown of glucose to make ATP glucose C-C-C-C-C-C fructose-1,6bP P-C-C-C-C-C-C-P DHAP P-C-C-C G3P C-C-C-P hexokinase phosphofructokinase Those phosphates sure make it uncomfortable around here! C H P C P C ATP 2 ADP 2 activation energy

AP Biology Can’t store ATP  good energy donor, not good energy storage too reactive transfers P i too easily only short term energy storage  carbohydrates & fats are long term energy storage ATP / ADP cycle A working muscle recycles over 10 million ATPs per second Whoa! Pass me the glucose (and O 2 )! ATP ADP PiPi kcal/mole cellular respiration

AP Biology Cells spend a lot of time making ATP! What’s the point? The point is to make ATP!

AP Biology H+H+ catalytic head rod rotor H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ ATP synthase ATP But… How is the proton (H + ) gradient formed? ADP P +  Enzyme channel in mitochondrial membrane  permeable to H +  H + flow down concentration gradient  flow like water over water wheel  flowing H+ cause change in shape of ATP synthase enzyme  powers bonding of P i to ADP: ADP + P i  ATP

AP Biology That’s the rest of my story! Any Questions?