Living Metabolism Part 1 AP Biology Living Metabolism Part 1

Energy and Life Life requires energy to survive. The way that different organisms acquire this energy and use it to survive allows for diversity. In this unit we will look at energy, how energy is used by living organisms, and two processes that are fundamental to life.

Catabolism (Hydrolysis Reaction) Reactants Amount of energy released (G < 0) Free energy Energy Products Progress of the reaction Exergonic reaction: energy released

Catabolism - Exergonic Catabolism refers to the breaking down (hydrolysis) of a molecule. This process releases potential E stored in the chemical bonds of the molecule. This is an exergonic reaction, because heat is released into the environment. Cellular respiration is an example of a natural catabolic reaction.

Anabolism (Dehydration Synthesis) Products Amount of energy required (G > 0) Free energy Energy Reactants Progress of the reaction Endergonic reaction: energy required

Anabolism - Endergonic Anabolism refers to the assembly (dehydration synthesis) of molecules. This requires kinetic E to position monomers in a way that chemical bonds can be formed. This is an endergonic reaction, because energy is absorbed from the environment. Photosynthesis is an example of a natural anabolic reaction.

Energy Coupling Two processes united by Energy THIS IS THE BIG PICTURE IDEA OF THIS WHOLE UNIT!! The processes of cellular respiration and photosynthesis are “coupled” by energy. One process uses light energy to create organic molecules, and the other process breaks those organic molecules down to release energy. These processes need one another to continue. It is a fantastic cycle that drives all life on Earth. Life requires free energy to survive. But, what is free energy?

Catabolism (Hydrolysis Reaction) Reactants Amount of energy released (G < 0) Free energy Energy Products Progress of the reaction Exergonic reaction: energy released

Anabolism (Dehydration Synthesis) Products Amount of energy required (G > 0) Free energy Energy Reactants Progress of the reaction Endergonic reaction: energy required

Bioenergetics Video Link https://www.youtube.com/watch?v=nDCxIpiI7-Y

Free Energy – “Gibb’s” Gibb’s free energy is the energy that is available in a system to do work. Energy that is available to make ATP. ATP is used for the signal transduction pathway, moving materials around within the cell, moving materials across the membrane, and anabolic/catabolic reactions. The change is the free energy, determined by using the formula on the next slide, will be positive or negative, depending on the type of reaction.

Gibbs “Free” Energy Δ G = ΔH – TΔ S G- Gibbs “free” energy H – Enthalpy (Total usable energy in the system) T – Temperature in Kelvin (273 + C⁰) S- Entropy (Disorder created by something being broken down) Δ – Change in a variable over time ****Overall, the change in free energy is the final energy minus the initial energy in the system.****

Free Energy Not all energy is available as a result of a reaction! Much of the energy is lost as heat. However: If the Δ G is negative, then there is energy available to do work. This is the result of cellular respiration. (Catabolic, Exergonic) If the Δ G is positive, then there is energy that is not available. It is in the chemical bonds. This is the result of photosynthesis. (Anabolic, Endergonic)

Practice Problems Calculate the Gibbs free energy change (Δ G ) for the following chemical reaction: ATP  ADP + Pi The reaction occurs at 68 °C, the change in heat (Δ H) = 19,070 cal, and the change in entropy (Δ S) = 90 cal/K. Is the reaction anabolic or catabolic? Endergonic or exergonic?

68 °C = 341 K, therefore the equation is set up in the following way: Δ G = Δ H – T Δ S Δ G = 19,070 cal – (341 K) (90 cal/K) Δ G = –11,620 cal = –11.62 kcal

Practice Problems Calculate the Gibbs free energy change (Δ G) for the following chemical reaction: glutamate + NH3  glutamine + H2O The reaction occurs at 68 °C, the change in heat (Δ H) = 4103 cal, and the change in entropy (Δ S) = 2.4 cal/K. Is the reaction anabolic or catabolic? Endergonic or exergonic?

68 °C = 341 K, therefore the equation is set up in the following way: Δ G = Δ H – T Δ S Δ G = 4103 cal – 341 K (2.4 cal/ K) Δ G = 3284.6 cal = 3.3 kcal

Unstable (Capable of work) vs. Stable (no work) G < 0 G = 0 A closed hydroelectric system

Progress of the reaction LE 8-6a Reactants Amount of energy released (G < 0) Free energy Energy Products Progress of the reaction Exergonic reaction: energy released

Progress of the reaction LE 8-6b Products Amount of energy required (G > 0) Free energy Energy Reactants Progress of the reaction Endergonic reaction: energy required

Potential Energy vs. Kinetic Energy

Types of work performed by living cells Motor protein Protein moved Mechanical work: ATP phosphorylates motor proteins Membrane protein ADP ATP + P i P P i Solute Solute transported Transport work: ATP phosphorylates transport proteins P NH2 + NH3 Glu + P i Glu Reactants: Glutamic acid and ammonia Product (glutamine) made Chemical work: ATP phosphorylates key reactants

ATP

Phosphorylation